-
生物专业英语
（
Bioengineering
English
）
Lesson One
（
4
学时）
Inside the Living
Cell: Structure
and
Function
of Internal Cell Parts
Cytoplasm: The Dynamic, Mobile
Factory
细胞质：动力工厂
Most of the properties we associate
with life are properties of the
cytoplasm.
Much
of the
mass
of
a
cell
consists
of
this
semifluid
substance,
which
is
bounded
on
the
outside
by
the
plasma membrane.
Organelles are suspended
within it, supported by the filamentous network
of
the
cytoskeleton.
Dissolved
in
the
cytoplasmic
fluid
are
nutrients,
ions,
soluble
proteins,
and other
materials needed for cell functioning.
生命的大部分特征表现在细胞质的特征上。细胞质大部分由半流体物质组成，并由细胞膜
（原生质膜）包被。细胞器悬浮在其中，并由丝状的细胞骨架支撑。细胞质中溶解了大量
的营养物质，离子，可溶蛋白以及维持细胞生理需求的其它物质。
The Nucleus: Information
Central
（细胞核：信息中心）
The eukaryotic cell
nucleus
is the largest organelle and houses the
genetic material (DNA) on
chromosomes.
(In
prokaryotes
the
hereditary
material
is
found
in
the
nucleoid.)
The
nucleus
also
contains
one
or
two
organelles-the
nucleoli-
that
play
a
role
in
cell
division.
A
pore-
perforated sac called the
nuclear
envelope
separates the nucleus and its
contents from the
cytoplasm.
Small molecules can pass
through the nuclear envelope, but larger molecules
such
as mRNA and ribosomes must enter
and exit via the pores.
真核细胞的细胞核是最大的细胞器
，细胞核对染色体组有保护作用（原核细胞的遗传物质
存在于拟核中）。细胞核含有一或
二个核仁，核仁促进细胞分裂。核膜贯穿许多小孔，小
分子可以自由通过核膜，而象
mRNA
和核糖体等大分子必须通过核孔运输。
Organelles: Specialized Work
Units
（细胞器：特殊的功能单位）
1
生物专业英语
< br>（
Bioengineering
English
）
All
eukaryotic
cells
contain
most
of
the
various
kinds
of
organelles,
and
each
organelle
performs
a
specialized
function
in
the
cell.
Organelles
described
in
this
section
include
ribosomes, the endoplasmic reticulum,
the Golgi complex, vacuoles, lysosomes,
mitochondria,
and the plastids of plant
cells.
所有的真核细胞都含有多种细胞器，
每个细胞器
都有其特定功能。
本节主要介绍核糖体，
内质网，高尔基体系，
液泡，溶酶体，线粒体和植物细胞中的质体。
The
number of
ribosomes
within a
cell may range from a few hundred to many
thousands.
This quantity
reflects the fact that, ribosomes are the sites at
which amino acids are assembled
into
proteins for export or for use in cell processes.
A complete ribosome is
composed of one
larger and one smaller
subunit.
During protein
synthesis the two subunits move along a strand
of mRNA,
Several
ribosomes may become attached to a single mRNA
strand; such a combination is called
a
polysome.
Most
cellular
proteins
are
manufactured
on
ribosomes
in
the
cytoplasm.
Exportable
proteins
and
membrane
proteins
are
usually
made
in
association
with
the
endoplasmic reticulum. <
/p>
核糖体的数量变化从几百到几千，核糖体是氨基酸组装成蛋白质的重要场所。完整的核
糖体由大亚基和小亚基组成。核糖体沿着
mRNA
< br>移动并阅读遗传密码，翻译成蛋白质。一
条
mRNA
上可能有多个核糖体，
称多聚核糖体。
大多
数细胞蛋白是由细胞质中核糖体生产。
输出蛋白和膜蛋白通常与内质网有关。
The
endoplasmic
reticulum,
a lacy array of membranous
sacs, tubules, and vesicles, may be
either rough (RER) or smooth (SER).
Both types play roles in
the synthesis and transport of
proteins.
The
RER,
which
is
studded
with
polysomes,
also
seems
to
be
the
source
of
the
nuclear envelope after a
cell divides.
2
生物专业英语
（
Bioengineering
English
）
< br>内质网，带有花边的生物囊，有管状，泡状之分，以及光滑和粗糙面区别。两种都与蛋
白质的合成和运输有关。粗糙内质网上分布许多核糖体，也可能提供细胞分裂后所需的细
胞膜。
SER lacks polysomes;
it is active in the synthesis of fats and steroids
and in the oxidation of
toxic
substances
in
the
cell.
Both
types
of
endoplasmic
reticulum
serve
as
compartments
within
the
cell
where
specific
products can be
isolated and
subsequently
shunted
to
particular
areas in or
outside the cell.
光滑内质网上无核糖体，主要作用是脂肪和类固
醇的合成以及细胞内有毒物质的氧化。
两种内质网合成的产物在其中进行分流或运输到细
胞外。
Transport vesicles may
carry exportable molecules from the endoplasmic
reticulum to another
membranous
organelle, the
Golgi complex.
Within the Golgi complex
molecules are modified
and packaged for
export out of the cell or for delivery else where
in the cytoplasm.
运输小泡能够将可运输分子从内质网运输到高尔
基复合体上。在高尔基复合体中修饰，
包装后输出细胞或传递到细胞质中的其他场所。<
/p>
Vacuoles
in
cells
appear
to
be
hollow
sacs
but
are
actually
filled
with
fluid
and
soluble
molecules.
The
most
prominent
vacuoles
appear
in
plant
cells
and
serve
as
water
reservoirs
and
storage
sites
for
sugars
and
other
molecules.
Vacuoles
in
animal
cells
carry
out
phagocytosis
(the intake of
particulate matter) and
pinocytosis
(vacuolar drinking).
细胞中的液泡好
象是中空的，
但实际上充满了液体和可溶分子。
最典型的液泡存
在于植
物细胞中，储备水，糖以及其它分子。动物中的液泡起吞噬和胞饮作用。
A
subset
of
vacuoles
are
the
organelles
known
as
lysosomes,
which
contain
digestive
enzymes
(packaged
in
lysosomes
in
the
Golgi
complex)
that
can
break
down
most
biological
macromolecules.
They act to digest food
particles and to degrade damaged cell parts.
溶酶体是液泡亚单位，
含有消化酶，
降解大部分生
物大分子。
消化食物微粒和降解损伤
的细胞残片。
3
生物专业英语
（
Bioengineering
English
）
Mitochondria
are the sites
of energy-yielding chemical reactions in all
cells.
In addition,
plant cells contain
plastids
that utilize light energy to
manufacture carbohydrates in the process
of photosynthesis.
It is on the large surface area
provided by the inner cristae of mitochondria
that ATP-generating enzymes are
located.
Mitochondria are
self-replicating, and probably they
are
the evolutionary descendants of what were once
free-living prokaryotes.
线粒体是细胞中化学产能的场所
。
另外，
植物细胞中的质体在光合作用中利用光能产生
碳水化合物，线粒体内嵴上提供了很大的表面积并分布着产
ATP
酶。线粒体自我复制，并
且可能是自由生活的原核生物在进化中形成的
后代。
There are two types of
plastids: leucoplasts, which lack pigments and
serve as storage sites
for starch,
proteins, and oils; and chromoplasts, which
contain pigments.
The most
important
chromoplasts
are <
/p>
chloroplasts-
organelles
that
contain
the
chlorophyll
used
in
photosynthesis.
The
internal
structure
of
chloroplasts
includes
stacks
of
membranes
called
grana,
which
are
embedded in a matrix called the
stroma.
质体有两种类型：白色体，缺乏色素，是淀粉
，蛋白质和油的储备场所；色质体，含有
色素。叶绿体是最重要的色质体，含有与光合作
用有关的叶绿素。叶绿体的内部结构是由
多层膜形成的叶绿体基粒，其中包埋在基质中的
基粒称子座。
The
Cytoskeleton
（细胞骨架）
All eukaryotic cells have a
cytoskeleton, which is a convoluted latticework of
filaments and
tubules that appears to
fill all available space in the cell and provides
support for various other
organelles.
A
large
portion
of
the
cytoskeleton
consists
of
threadlike
microfilaments
composed
mainly
of
the
contractile
protein
actin.
They
are
involved
in
many
types
of
intracellular movements in plant and
animal cells.
A second
protein,
myosin,
is involve
in the
contraction of muscle cells.
Another main structural
component of the cytoskeleton consists of
microtubules,
which
are
composed
of
the
globular
protein
tubulin
and
together
act
as
scaffolding
that
provides
a
stable
cell
shape.
Cytoskeletal
intermediate
filaments
appear
to
4
生物专业英语
（
Bioengineering
English
）
impart tensile strength to the cell
cytoplasm.
Mechanoenzymes
such as myosin,
dynein,
and
kinesin
interact
with
the
cytoskeletal
filaments
and
tubules
to
generate
forces
that
cause
movements.
所有的细胞都有细胞骨架，网络结构的
纤丝充满了它所能触及的全部空间并且对细胞器提
供支持作用。细胞骨架大部分由微丝组
成，微丝主要由可收缩的肌动蛋白组成。动植物细
胞的许多种类型细胞内运动与肌动蛋白
有关。第二类蛋白是肌球蛋白，它与肌肉细胞的收
缩有关。细胞骨架的另一个主要结构成
分是微管，由球状的微管蛋白组成，象脚手架一般
维持细胞的稳定形态。细胞骨架的中间
丝提供了细胞质伸缩动力。机械酶，例如，肌球蛋
白，动力蛋白，驱动蛋白与微丝，微管
相互作用产生动力而引起细胞运动。
Cellular
Movements
（细胞运动）
Although the cytoskeleton provides some
stability to cells, its microtubules and filaments
and
their associated proteins enable
cells to move by creeping or gliding.
Such movements require
a
solid substrate to which the cell can adhere and
can be guided by the geometry of the surface.
Some cells also exhibit
chemotaxis,
the ability
to move toward or away from
the source of a
diffusing
chemical.
尽管细胞骨架提供了细胞的某些稳定性，微丝，微管及相关蛋白能
使细胞爬行或滑动。
这种运动需要固体基质依托并通过表面几何形状的改变而运动。某些
细胞具备趋药性，即
趋向或逃离扩散开的化学源。
Certain eukaryotic cells can swim
freely in liquid environments, propelled by
whiplike
cilia
or
flagella.
Both
cilia
and
flagella
have
the
same
internal
structure:
nine
doublets
(pairs
of
microtubules)
are
arranged in a ring and
extend the length of the cilium or flagellum, and
two
more microtubules run down the
center of the ring. Every cilium or flagellum
grows only from
the
cell
surface
where
a
basal
body
is
located.
Movement
is
based
on
the
activities
of
tiny
dynein side arms that
extend from one of the microtubules of each
doublet.
5
生物专业英
语
（
Bioengineering
English
）
< br>某些真核细胞能在液体液体中自由运动，
由纤毛或鞭毛推动。
纤毛和鞭毛具有同样的内
部结构：九个双微管环形排列，纵向延伸，环中心是两个或
以上微管组成。纤毛或鞭毛从
细胞表面的基体出生长，双微管的动力蛋白臂从一侧延伸到
另一侧而引起运动。
Nutrients,
proteins,
and
other
materials
within
most
plant
cells
are
moved
about
via
cytoplasmic
streaming.
The
process
occurs
as
myosin
proteins
attached
to
organelles
push
against
microfilaments
arrayed
throughout
the
cell.
Microfilaments
and
microtubules
are
responsible for almost all
major
cytoplasmic movements.
During cell division, microtubules of
the
spindle
assembled
from
tubutin
subunits
near
organelles
called
centrioles
move
the
chromosomes.
大部分植物细胞的营养，蛋白质和其它物质由细胞质流运输。这个过程是由于依附在细
胞器上的肌球蛋白反推排列在细胞周围的微丝形成的。
绝大部分细胞质
运动由微丝和微管
完成。
在细胞分裂期间，
中心粒周围的由微管蛋白亚基装配形成的纺锤体微管移向染色体。
Glossary
cytoplasm
（细）胞质
The
living
contents
of
a
cell
bounded
externally by the plasmalemma,
including an
aqueous
ground
substance
(hyaloplasm,
cell
sap, or cell
matrix)
containing organelles and
various
inclusions
but
excluding
the
nucleus
and visible
vacuoles.
cytoskeleton
细胞骨架
Of
eukaryotic
cells,
an
internal
Its
microtubules
and
other
components
structurally
support
the
cell,
organize
and
move
its
inteftial
components.
The
cytoskeleton also helps free-living
cells move
through their environment.
nucleus
细胞核，核
(
复数
nuclei
)
The organelle of the eukaryote cell
that
contains
the
chromosomes and hence
ultimately controls cellular activity
and
inheritance through the activity of
the genetic
material, DNA
chromosome
染色体
6
生物专业英语
< br>（
Bioengineering
English
）
A DNA-histone thread residing in the
nucleus
of a cell.
Each chromosome possesses two
telomeres and a centromere, and some
contain a nucleolus organizer.
RNA
proteins are
invariably associated with the
chromosome.
nucleoid
拟核，类核，核质体
The DNA-containing area of a prokaryote
cell, analogous to the eukaryote
nucleus but
not membrane bounded.
nucleoli
核仁
(
单数
nucleolus
)
Nuclear structures composed
of completed or
partially completed
ribosomes and the
specific parts of
chromosomes that contain
the infon-
nation for their construction.
nuclear envelope
核膜，核被膜
A double
membrane (two lipid bilayers and
associated proteins) that is the
outermost
portion of a cell nucleus.
ribosome
核糖体
Small
structures composed of two protein and
ribonucleic acid subunits involved in
the
assembly of proteins from amino
acids.
polysome
多核糖体
Of protein synthesis, several ribosomes
all
translating the same messenger RNA
molecule,one after the other.
endoplasmic reticulum
内质网
Folded
membranes
and
tubes
throughout
the
eukaryotic
cell
that
provide
a
large
surface
upon which chemical activities take
place.
Golgi complex
高尔基复合体
A
stack
of
flattened,
smooth,
membranous
sacs;
the
site
of
synthesis
and
packaging
of
certain molecules in eukaryotic cells.
vacuole
液泡
Storage
container within the cytoplasm of a
cell having a surrounding
membrane.
phagocytosis
吞噬作用
The process
by which the cell wraps around a
particle and engulfs it.
pinocytosis
胞饮作用
The process
by which a cell engulfs some
molecules
dissolved in water
lysosome
溶酶体
A
specialized
organelle
that
holds
a
mixture
of hydrolytic
enzymes.
mitochondrion
线粒体
(
复数
mitochondria
)A membranous
organelle
7
生物专业
英语
（
Bioengineering
English
）
resembling a small bag with a larger
bag
resembling a small bag with a
larger bag
inside that is folded back
on itself; serves as
the site of
aerobic cellular respiration.
plastid
质体
An organelle present in all plants
except
bacteria, blue-green algae, and
fungi; it is
enclosed by two membranes
(the envelope)
and has various
functions
chloroplast
叶绿体
A
plastid in which photosynthesis is carried
out. Chloroplasts occur in all
photosynthetic
organisms except
photosynthetic bacteria
blue-green
algae.
stroma
基质，子座（复数
stromata
）
Region within a chloroplast that has no
chlorophyll.
microfilament
微丝，纤丝
Long,
fiberlike structures made of protein and
found in cells, often in close
association with
the microtubules;
provide structural support
and enable
movement.
actin
肌动蛋白
A globular contractile
protein. In muscle
cells, actin
interacts with another protein,
myosin,
to bring about contraction.
myosin
['maiesin]
肌球蛋白
A protein that, with actin, constitutes
the
principal element of the
contractile apparatus
of muscle.
microtubute
微管
Small, hollow tubes of protein that
function
throughout the cytoplasm to
provide
structural support and enable
movement.
tubulin
微管蛋白
A protein that is the major constituent
of
microtubules.
dynein
动力蛋白，动素
A
group
of
at
least
four
distinct
proteins
found
in
the
flagella
and
microtubules
of
eukaryotic
cells
and
possessing
ATPase
activity.
chemotaxis
趋化性
A locomotory
movement of an organism or
cell in
response to, and directed by, an
directional stimulus.
cilia
纤毛
8
生物专业英语
（
Bioenginee
ring
English
）
Numerous short, hairlike structures
projecting
from the cell surface that
enable locomotion.
flagella
鞭毛
(<
/p>
单数
flagellum
)
Long,
hairlike
structures
projecting
from
the
cell
surface that enable locomotion.
basal
body
基体
A body
identical in structure to a centriole,
found
always
at
the
base
of
a
cilium or eukaryote flagellum.
centriole
中心粒
An organelle located close to the
nucleus in
most animal and lower plant
cells but absent
from prokaryotes and
higher plants.
9
生物专业英语
（
Bioengineering
English
）
Lesson Two
（
2
学时）
Photosynthesis
Photosynthesis
occurs
only
in
the
chlorophyll-containing
cells
of
green
plants,
algae,
and
certain
protists
and
bacteria.
Overall,
it
is
a
process
that
converts
light
energy
into
chemical
energy
that
is
stored
in
the
molecular
bonds.
From
the
point
of
view
of
chemistry
and
energetics,
it
is
the
opposite
of
cellular
respiration.
Whereas
cellular
respiration
is
highly
exergonic and
releases energy, photosynthesis requires energy
and is highly endergonic.
光合作用只发生在含有叶绿素
的绿色植物细胞，海藻，某些原生动物和细菌之中。总体
来说，这是一个将光能转化成化
学能，并将能量贮存在分子键中，从化学和动能学角度来
看，它是细胞呼吸作用的对立面
。细胞呼吸作用是高度放能的，光合作用是需要能量并高
吸能的过程。
< br>
Photosynthesis starts with
CO
2
and
H
2
O as raw materials and
proceeds through two sets of
partial
reactions.
In
the
first
set,
called
the
light-
dependent
reactions,
water
molecules
are
split (oxidized), 0
2
is released, and ATP and NADPH are
formed.
These reactions
must take
place in the presence of
light energy.
In the second
set, called
light-independent
reactions,
CO
2
is
reduced (via the addition of H atoms) to
carbohydrate.
These
chemical events rely on
the electron
carrier NADPH and ATP generated by the first set
of reactions.
光合作用以二氧化碳和水为原材料并经历两步化学反应。
第一步，
称光反应，
水分子分
解，氧分子释放，
ATP
和
NADPH
形成。此反应需要光能的存在。第二步，称暗反应，二氧
化碳被还原成碳水化合物，这步反应依赖电子载体
NADPH
< br>以及第一步反应产生的
ATP
。
Both sets of reactions take place in
chloroplasts.
Most of the enzymes and pigments for
the
lightdependent reactions are
embedded in the
thylakoid
membrane of chloroplasts.
The dark
reactions take
place in the stroma.
10
生物专业英语
（
Bioengineerin
g
English
）
两步反应都发生在叶绿体中。光反
应需要的大部分酶和色素包埋在叶绿体的类囊体膜
上。暗反应发生在基质中。
How Light Energy Reaches
Photosynthetic
Cells
（光合细胞如何吸收光能的）
The energy in light
photons
in the visible part of the spectrum can
be captured by biological
molecules
to
do
constructive
work.
The
pigment
chlorophyll
in
plant
cells
absorbs
photons
within
a
particular
absorption
spectrums
statement
of
the
amount
of
light
absorbed
by
chlorophyll
at
different
wavelengths.
When
light
is
absorbed
it
alters
the
arrangement
of
electrons
in
the
absorbing
molecule.
The
added
energy
of
the
photon
boosts
the
energy
condition
of
the
molecule
from
a
stable
state
to
a
less-stable
excited
state.
During
the
light-dependent
reactions
of
photosynthesis,
as
the
absorbing
molecule
returns
to
the
ground
state,
the
excitation
energy
is
transmitted
to
other
molecules
and
stored
as
chemical
energy.
生物分子能捕获可见光谱中的光能。植物细胞中叶绿素在不同光波下吸收部分吸收光
谱。
在吸收分子中，光的作用使分子中的电子发生重排。光子的能量激活了分子的能量状
态，
使其从稳定态进入不稳定的激活态。
All
photosynthetic
organisms
contain
various
classes
of
chlorophylls
and
one
or
more
carotenoid
(accessory)
pigments
that
also
contribute
to
photosynthesis.
Groups
of
pigment
molecules called
antenna
complexes
are present on thylakoids.
Light striking any one of the
pigment
molecules
is
funneled
to
a
special
chlorophyll
a
molecule,
termed
a
reaction-center
chlorophyll,
which
directly
participates
in
photosynthesis.
Most
photosynthetic
organisms
possess
two
types
of
reaction-center
chlorophylls,
P680
and
P700,
each
associated
with
an
electron acceptor
molecule and an electron donor.
These aggregations are known
respectively
as
photosystem
Ⅰ
(P700) and
photosystem
Ⅱ
(P680).
所有的光合作用生物含有不同等级的叶绿素和
一个或多个类胡萝卜素
（光合作用的辅助
色素）。称作天线复合
体的色素分子群存在于类囊体中。激活色素分子的光能进入叶绿素
11
生物专业英语
（
Bioengineering
English
）
< br>反应中心，其直接参与光合作用。大部分光反应细胞器拥有两套反应中心，
P68
0
和
P700
，
每个光系统都含有一个电子受体和电子供体。这些集合体就是大家熟识的光合系统Ⅰ和光
合系统Ⅱ
。
The Light-Dependent Reaction:
Converting Solar Energy into Chemical-Bond Energy
光反应：光能转化成化学键能
The
photosystems of the light-dependent reactions are
responsible for the packaging of light
energy in the chemical compounds ATP
and NADPH.
This packaging
takes place through a
series of
oxidation reduction reactions set in motion when
light strikes the P680 reaction center
in photosystem
Ⅱ
.
In this initial event water
molecules are cleaved, oxygen is released, and
electrons are donated.
These electrons are accepted first by
plastoquinone and then by a series
of
carriers as they descend an electron transport
chain.
For each four
electrons that pass down
the chain, two
ATPs are formed.
The last
acceptor in the chain is the P700 reaction center
of
photosystem
Ⅰ
.
At this point incoming photons boost the energy of
the electrons, and they are
accepted by
ferredoxin.
Ferredoxin is
then reoxidized, and the coenzyme
NADP
+
is reduced to
the
NADPH.
The
ATP
generated
previously
and
the
NADPH
then
take
part
in
the
light
independent reactions.
光反应的光
系统将光能转化成化学复合物
ATP
和
NADPH
。
当光激活光系统Ⅱ的光反应中
心时，通过一系列的氧化还原反应实现能量的传递。反应开始时，水被分解，氧被释放并
提供电子。电子首先传递给质体醌，然后通过一系列载体形成的电子传递链。每传递
4
个
电子，形成
2
个
ATP
。最后一个受体存在于光反应系统Ⅰ的反应中心里
。此处光子激活电
子，电子传递给铁氧还蛋白。铁氧还蛋白再氧化，并且辅酶
NADP
还原成
NADPH
。早期产
生的
ATP
和
NADPH
进入暗反应。
The
production
of
ATP
from
the
transport
of
electrons
excited
by
light
energy
down
an
electron
transport
chain
is
termed
photophosphorylation.
The
one-way
flow
of
electrons
through
photosystems
II
and
I
is
called
noncyclic
photophosphorylation;
plants
also
derive
+
12
生
物专业英语
（
Bioengineering
English
）
additional
ATP
through
cyclic
photophosphorylation,
in
which
some
electrons
are
shunted
back through the
electron transport chain between photosystems
Ⅱ
and
Ⅰ
.
由电子传递链偶连产生
ATP
的过程称为光合磷酸化。通过光合系统Ⅱ流经光合系统Ⅰ的
电子路径称非循环式光合磷酸化；植物通过循环式光合磷酸化获得额外的
ATP
，一些电子
在光合系统Ⅰ和Ⅱ之间的电子传递链中回流
。
The Light-Independent
Reactions: Building Carbohydrates
暗反应：碳水化合物的形成
In
the light-independent reactions of photosynthesis,
which are driven by ATP and NADPH,
C0
2
is
converted to
carbohydrate.
The reactions
are also known as the
Calvin-Benson
cycle.
Atmospheric
CO
2
,
is
fixed
as
it
reacts
with
ribulose
biphosphate
(RuBP),
a
reaction
that
is
catalyzed
by
the
enzyme
ribulose
biphosphate
carboxylase.
The
reduction
Of
C0
2
to
carbohydrate (fructose
diphosphate) is completed via several more steps
of the cycle.
Finally,
RUBP is regenerated so that the cycle
may continue.
由
ATP
和
NADPH
驱动的暗反应中，
二氧
化碳转化成碳水化合物。
即卡尔文循环。
二磷酸
核酮糖固定二氧化碳，由二磷酸核酮糖羧化酶催化。
Oxygen: An Inhibitor of
photosynthesis
（氧：光合作用的抑制因子）
High
levels
of
oxygen
in
plant
cells
can
disrupt
photosynthesis
and
can
also
cause
photorespiration-
an
inefficient fun of the dark reactions in which
0
2
is
fixed rather than C0
2
and
no carbohydrate is
produced.
Reprieve from
Photorespiration: The C
4
Pathway
Most plants are
C
3
plants;
they experience decreased carbohydrate
production under hot, dry
conditions as
a result of the effects of photorespiration.
Among
C
4
plants,
however, special
leaf
anatomy
and
a
unique
biochemical
pathway
enable
the
plant
to
thrive
in
and
conditions.
Thus
C
4
plants
lessen
photorespiration
by
carrying
out
photosynthesis
only
in
cells
that
are
insulated from high
levels of CO
2
.
They also possess a novel mechanism for
carbon fixation.
13
生物专业英语
（
Bioengineering
English
）
大部分植物是碳
< br>3
植物，在高温干旱条件下，由于光呼吸作用而使碳水化合物的合成降低。而在大
多数
的碳
4
植物中，由于叶脉的特殊构
造和独特的化学路径使植物依然很茂盛。这是碳固定的一个新机制。
Glossary
14
生物专业英语
（
Bioengineering
English
）
light-dependent reactions
光反应
-
The first
stage in photosynthesis, driven by
light
energy.
Electrons
that
trap
the
sun's
energy pass the energy to high-energy
carriers
such as ATP or NADPH, where it
is stored in
chemical bonds.
light-independent reactions
暗反应
The
second
stage
of
photosynthesis,
also
called
the
Calvin-Benson
cycle,
which
does
not
require light.
During the
six steps of the
cycle,
carbon
is
fixed
and
carbohydrates
are
formed.
chloroplast
叶绿体
A plastid in which photosynthesis is
carried
out.
Chloroplasts occur in all
photosynthetic
organisms
except
photosynthetic
bacteria
and
blue-green algae.
absorption
spectrum
吸收光谱，吸收谱
The spectrum obtained when radiation
(light, ultraviolet radiation, etc.)
from a source
A
plant
in
which
the
light-independent
giving a
continuous spectrum is passed
reactions
of
photosynthesis
start
with
a
through a substance.
Calvin-
Benson cycle
卡尔文·本森循环
Cyclic
reactions that are the
of the light-
independent reactions of
A
plant
such
as
corn
in
which
the
light
photosynthesis.
In land plants, RUBP, or
independent
reactions
of
photosynthesis
star
some other compound to
which carbon has
with a
four-carbon compound.
been affixed,
under goes rearrangements that
lead to formation of a sugar phosphate
and to
15
regeneration of the RUBP.
The cycle runs
on ATP and
NADPH from light-dependent
reactions.
carotenoid
类胡萝卜素
Light-sensitive,
accessory pigments
that
transfer absorbed
energy to chlorophylls.
They absorb violet and blue wave-
lengths but
transmit red, orange, and
yellow.
chlorophyll
叶绿素
The green
substance of plants by which
photosynthesis is accomplished; it is
usually localized in intracellular
organelles
called chloroplasts.
cyclic photophosphorylation
环形光合磷酸化（作用）
Cyclic photophosphorylation is coupled
to
cyclicelectron flow, in which ATP is
the only
product.
C
3
plant
三碳植物
threecarbon
compound.
Most
plants
are
C
3
plants.
C
4
plant
四碳植物
生物专业英语
（
Bioengineering
English
）
noncyclic photophosphorylation
非环形光合磷酸化作用
Noncyclic photophosphorylation is
coupled
to noncyclic electron flow, the
electrons being
used to reduce
NADP
+
as well as to make
ATP.
photon
光子
A particle
that has zero mass or charge and
unit
spin, the quantum of the electromagnetic
field and carrier of the
electromagnetic force.
photophosphorylation
光合磷酸化作用
The
synthesis of ATP from phosphate and
ADP
during photosynthesis, using light
energy.
photorespiration
光呼吸
A
light-dependent type of respiration that
occurs in most photosynthetic plants
and
differs from normal (or dark)
respiration.
photosynthesis
光合作用
The
synthesis
of
organic
compounds
by
reduction of carbon
dioxide using light energy
absorbed by
chorophyll.
photosystem
光合系统
One
of
the
clusters
of
light-trapping
pigments
embedded
in
photosynthetic
pathways.
ribulose
biphosphate
(RUBP)
核
酮糖二磷酸
A
compound
with
a
backbone
of
five
carbon
atoms
that
is
required
for
carbon
fixation
in
the
Calvin-Benson
cycle
of
photosynthesis.
thylakoid
类囊体
One of a
number of flattened fluid-filled sacs
that
form
the
photosynthetic
lamellar
system
of
chloroplasts,
photosynthetic
bacteria,
and
blue-green algae.
membranes.
Photosystem
I
operates
during
the cyclic pathway; photosystem
Ⅱ
operates
during
both
the
cyclic
and
noncyclic
16
生物专业英语
（
Bioengineerin
g
English
）
Lesson Three
（
2
学时）
Cellular Reproduction:
Mitosis and Meiosis
The Nucleus and
Chromosomes
The cell nucleus
is the main repository of genetic information.
Within the nucleus are the
chromosomes tightly coiled strands of
DNA and clusters of associated proteins.
Long stretches
of the continuous DNA molecule wind
around these clusters of proteins, or
histones,
forming
beadlike
complexes
known
as
nucleosomes.
More
coiling
and
supercoiling
produces
a
dense
chromosome
structure.
Each
long
strand
of
DNA
combines
with
histones
and
nonhistone
proteins to make
up the substance
chromatin.
细胞核是贮藏遗传信息的主要场所。
DNA
盘绕成螺旋线以及相
关的成簇蛋白质。
DNA
螺旋线缠绕成簇的组蛋白形成珠链状的
核小体。
这些螺旋和超螺旋形成致密的染色体组结
构。每个长链
DNA
与组蛋白和非组蛋白一起构成染色质物质。
A pictorial display of an
organism's chromosomes in the coiled, condensed
state is known
as
a
karyotype.
Karyotype
reveal
that
in
most
cells
all
but
sex
chromosomes
are
present as
two
copies,
referred
to
as
homologous
pairs.
Non-sex
chromosomes
are
called
autosomes.
Organisms whose cells
contain two sets of parental chromosomes are
called
diploid;
those with
cells containing a single set of
parental chromosomes are called
haploid.
染色体致密的超螺旋状态我们称染色体组。除了性染色体外，
大多数细胞的染色体组成对出
现，称同源染色体对。非性染色体称常染色体。生物细胞含
有两套父母本染色体的称二倍体；
含有单套染色体的称单倍体。
The Cell Cycle
The
cell
cycle
is
a
regular
sequence
in
which
the
cell
grows,
prepares
for
division,
and
divides to form two daughter cells,
each of which then repeats the cycle.
Such cycling in effect
17
生物专业英语
（
Bioengineering
English
）
makes
single-celled
organisms
immortal.
Many
cells
in
multicellular
organisms,
including
animal muscle and nerve cells, either
slow the cycle or break out of it altogether.
在细胞生长过程中，细胞循环遵循特定程序，分裂准备，分裂成
2
个子细胞，子细胞
再循环。此循环使得单细胞永生。多细胞生物中的许
多细胞，包括动物肌肉和神经细胞，
要么降低循环速度，要么同时分裂。
The
normal
cell
cycle
consists
of
four
phases.
The
first
three
include
G
1
,
the
period
of
normal metabolism; S phase, during
which normal synthesis of biological molecules
continues,
DNA
is
replicated,
and
histones
are
synthesized;
and
G
2
,
a
brief
period
of
metabolism
and
additional growth.
Together the G
1
,
S, and G
2
phases are called
interphase.
The
fourth phase
of
the
cell
cycle
is
M
phase,
the
period
of
mitosis,
during
which
the
replicated
chromosomes
condense
and
move
and
the
cell
divides.
It
is
believed
that
properties
of
the
cell
cytoplasm
control the cell cycle, along with
external stimulators and inhibitors such as
chalones.
正常细胞循环由
4
个时期组成。
头三期包括
G
1
,
正常新陈代谢；<
/p>
S
期
,
正常新陈
代谢同时，
DNA
复制，组蛋白合成；
G
2
期，短期的新陈代谢和少许生长
。
G
1
, S,
和
G
2
称分裂间期。最后
是
M
期，有丝分裂期，复制的染色体组浓缩，移
动并细胞分裂。据称是染色质控制了细胞
循环，伴随外部激活因子和抑制因子如抑素。<
/p>
Mitosis: Partitioning the
Hereditary Material
Biologists
divide
the
mitotic
cycle
into
four
phases.
At
the
beginning
of
prophase
the
chromosomes
each
consist
of
two
highly
condensed
chromatids
attached
to
each
other
at
a
centromere.
As prophase ends and
metaphase
begins, the
condensed chromosomes become
associated
with the
spindle.
Eventually the chromosomes become
arranged in a plane (called
the
metaphase
plate)
at
a
right
angle
to
the
spindle
fibers.
Next,
during
anaphase,
the
two
sister chromatids of each chromosome
split, and one from each pair is drawn toward each
pole
of
the
cell.
During
telophase
nuclear
envelopes
begin
to
form
around
each
set
of
chromosomes, and division
of the cytoplasm takes place.
18
生物专业英语
（
Bioengineering
English
）
< br>生物学家将有丝分裂划分为
4
个阶段。分裂前期，高度浓
缩的两个染色单体通过着丝
粒连接在一起。在分裂前期后期和分裂中期前期，浓缩的染色
体与纺锤体相连，最后以正
确的角度排列在赤道板上。在分裂后期，两个姊妹单体分离，
分别拽向细胞两极。在分裂
末期，在每套染色体周围形成核膜，细胞质发生分裂。
As
mitosis
proceeds,
the
spindle
microtubules
play
a
crucial
role
in
ensuring
that
both
paired
and separated chromatids move in the right
directions at the proper times.
Each half of
the spindle
forms as microtubules extend from each pole of a
dividing cell to the region of the
metaphase
plate.
During
prophase,
other
microtubules,
the
centromeric
fibers,
extend
outward
from
the
spindle
poles
to
structures
on
the
chromosomes
called
kinetochores.
During anaphase the fibers begin to
shorten, and the chromatids begin to move apart. <
/p>
在有丝分裂过程中，是纺锤体微管确保了染色单体在适当时间以正确方向进行分离。
纺锤体微管由两极向赤道板延伸。在分裂前期，其它微管，着丝粒纤维延伸到染色体的
动粒。在分裂后期，纤维开始变短，染色单体分离。
The spindle forms differently in plant
and animal cells.
In
animals it is associated with
centriole,
while
in
plant
and
fungal
cells
spindle
formation
is
associated
with
reions
called
microtubule
organizing centers.
植物和
动物细胞形成的纺锤体不同。动物细胞与中心粒相连，而在植物和真菌细胞中，纺
锤体与
微管组织中心的离子相连。
Cytokinesis: Partitioning the
Cytoplasm
胞质分裂：细胞质分离
The
division of the cell cytoplasm at the end of
mitosis is called
cytokinesis.
In animal
cells
it takes place as a ring of actin filaments
contracts around the cell equator, pinching the
cell
in two.
In
plant cells, which are bounded by a cell wall,
cytokinesis involves the building of a
19
生物专业英语
（
Bioengineering
English
）
new
cell plate
across the dividing cell at its
equator.
Cell wall material
is then deposited in the
region of the
cell plate.
在动物细胞中，环形肌动蛋白丝延赤道板收缩而使细胞一分为二。在植物细胞中，在
赤道板形成新的细胞板。
Meiosis:
The Basis of Sexual Reproduction
Meiosis
is
a
special
form
of
cell
division
that
takes
place
in
the
reproductive
organs
that
produce sex cells.
Like mitosis, it takes
place after DNA replication has occurred and
involves
two
sequential
nuclear
divisions
(meiosis
I
and
meiosis
Ⅱ
).
These
divisions
result
in
four
daughter cells, each with half the
number of chromosomes of the parent cell.
The phenomenon
of
crossing
over
during
meiosis
results
in
exchanges
of
genetic
information
between
chromosomes.
Hence, the homologous
chromosomes distributed to different progeny cells
are
not identical.
减数分裂是性细胞分
裂的特殊形式。如有丝分裂，它也是发生在
DNA
复制后并有连
续
的两个核分裂。产生
4
个子细胞，分
别含有亲本一半的染色体数。
As
in
mitosis
two
chromatids
exist
for
each
chromosome
at
the
beginning
of
prophase
1.
During this phase the homologous
chromosomes undergo synapsis, or pairing, which is
brought
about
by
a
bridging
structure
of
proteins
and
RNA
called
the
synaptonemal
complex.
The
homologous
pairs stay together when they align on the
metaphase plate.
Unlike the
anaphase
of mitosis, however, during
anaphase I the two chromatids of each chromosome
stay joined at
the centromere and move
together to one of the two poles of the cell.
It is this event that
results
in the halving of the
chromosome number in the four daughter cells that
result from meiosis.
正如在有丝分裂中一样，两个同源染色单
体通过蛋白质和
RNA
桥配对形成联会复合体。
与有丝分裂不同的是，
每组染色体的两个染色单体连接在着丝点上并一起移向细
胞两极的
一级。由此而导致
4
个子细胞
染色体数减半。
20
生物专业英语
（
Bioengineering
English
）
During telophase I nuclear envelopes
enclose the chromosomes in nuclei, and in most
species
cytokinesis
(the
first
nuclear
division)
follows.
The
second
nuclear
division
begins
with
metaphase
Ⅱ
, in
which the chromosomes in each daughter cell again
align on a metaphase plate.
The
centromeres
finally
divide,
and
each
sister
chromatid
moves
to
one
of
the
poles
of
the
spindle.
The next phase is telophase , followed
again by cytokinesis.
The
result of the entire
process is four
haploid cells in which parental chromosomes are
randomly distributed.
第二次核分裂开始于分裂中期，
子细胞中染色体重新排列在赤道板上。
着丝粒最终分离，
每个姊妹染色单体分向两极。接着胞质分裂。产生
4
个单倍体，父母染色体随机分配。
Asexual
Versus Sexual Reproduction
Mitosis
and
meiosis,
respectively,
make
simple
cell
division
and
sexual
reproduction
possible.
Each
means
of
passing
on
hereditary
information
has
advantages.
In
asexual
reproduction
the
parent
organism
gives
rise
to
offspring
that
are
genetic
clones
of
the
parent.
The
advantages of this type of reproduction are that
it preserves the parent's successful genetic
complement, requires little or no
specialization of reproductive organs, and is more
rapid than
sexual
reproduction.
A
major
disadvantage
of
the
asexual
mode
is
that
a
single
catastrophic
event or
disease may destroy an entire population of
genetically identical organisms.
A prime
benefit of sexual
reproduction is that it provides genetic
variability and a ready mechanism for
the elimination of deleterious
mutations.
It also allows
through populations.
有丝分裂和减数分裂在传递遗传信
息过程中各有优势。体细胞的繁殖就是父母本的克隆，其
优势是保留了父母本的成功遗传
信息，不需要特殊器官，比性复制快的多。但一个简单灾难性
事件或疾病都可能摧毁一个
细胞群体。
性复制的优势是它提供了遗传可变性和现存排除有害突
变的机制。也可以产生新的基因并在种群中蔓延。
Glossary
mitosis
有丝分裂
21
生物专业英语
（
Bioengineering
English
）
Process that results in equal and
identical distribution of replicated
chromosomes into
two newly
formed nuclei.
meiosis
减数分裂
The process
by which a nucleus divides
into four
daughter nuclei, each containing
half
the number of chromosomes of the
parent
nucleus.
histone
组蛋白
One of a
group of simple proteins that
have a
high content of the basic amino
acids
arginine or lysine and are found
associated with nucleic acids in the
chromatin of eukaryotic cells.
nucleosome
核小体
The basic unit of chromatin structure
in
eukaryotic cells.
A nucleosome consists of
eight histone molecules of four
different
types, together with about
140 base pairs of
DNA coiled around it.
main constituents of chromatin, most of
the
protein being histone.
karyotype
核型，染色体组型
,
The appearance of the chromosome
complement of an organism or cell.
homologous pair
同源染色体对
Chromosomes that pair during
meiosis.
Each
homologue is a duplicate
of one of the
chromosomes contributed at
syngamy by
the mother or father.
Homologous chromosomes contain the
same linear sequence of genes and as a
consequence each gene is present in
duplicate.
diploid
二倍体
Any nucleus, cell, or organism that
possesses twice the haploid number of
chromosomes.
haploid
单倍体
Any nucleus,
cell, or organism that
possesses a
single set of unpaired
chromosomes,
interphase (cycle)
分裂间期（周期）
In a
cell preparing to duplicate, the
interphase stage can divided into a
period
chromatin
染色质
The material
of which the chromosomes
are composed.
DNA and protein are the
22
生物专业英语
（
Bioengineering
English
）
of initial growth
(G
1
), a period of DNA
synthesis (S), and a second growth
period
(G
2
).
chalone
抑素
Substances found in mammalian tissue
homogenates that, when applied to
intact
tissue cells, inhibit mitosis,
particularly in
the presence of
adrenaline and
corticosteroids.
prophase
（分裂）前期
First stage of mitosis, during which
individual chromosomes become visible.
chromatid
染色单体
A replicated chromosome physically
attached to an identical chromatid at
the
centromere.
centromere
着丝粒
The small
area of a chromosome that
does not
stain with basic dyes during
mitosis
and meiosis; at interphase it is
cytokinesis
胞质分裂
cell plate
细胞板
single while the rest of the chromosome
is
made up of two chromatids.
metaphase
（分裂）中期
Second stage in mitosis, during which
the
chromosomes align at the equatorial
plane.
spindle
纺锤体
An array of
microtubutes extending
from pole to
pole and used in the movement
of
chromosomes.
metaphase plate
赤道板，中期板
The
grouping of the chromosomes in a
plane
at the equator of the spindle during
the metaphase stage of mitosis.
anaphase
分裂后期
The third stage of mitosis, during
which
the centromeres split and the
chromosomes
move to the poles.
telophase
（分裂）末期
Last stage in mitosis during which
daughter nuclei are formed.
Division of the cytoplasm of one cell
into two
new cells.
23
生物专业英语
（
Bioengineering
English
）
A plant cell structure that begins to
form
in the center of the cell and
proceeds to the
cell membrane,
resulting in cytokinesis.
Lesson Four
（
2
学时）
Foundations of Genetics
Early Theories
of inheritanee
24
生物专业英语
（
Bioengineering
English
）
Early ideas of inheritance included
Hippocrates' theory of
pangenesis
and August Weismands
germ
plasm
theory.
Based
on
experiments
with
mice,
Weismann
proposed
that
hereditary
information
in
gametes
transmitted
traits
to
progeny.
Both of
these
early
views
incorporated
the blending
theory: they held that heritable traits of the two
parents blend, so that the distinct
characteristics of each are lost in
offspring.
遗传学的
早期理论包括泛生说和种质理论。基于小鼠实验，维丝曼提出遗传信息储存在
配子中并将
遗传信息传递给后代。这两个早期观点合起来形成融合理论：子代拥有父母本
混合的遗传
特征，而不完全象亲代。
Gregor Mendel
and the Birth of Genetics
Gregor
Mendel,
an
Augustinian
monk
in
the
monastery
at
Brunn,
Austria,
is
known
as
the
university
student
and
having
a
background
in
mathematics,
Mendel
carried
out
a
series
of
carefully
planned
experiments
that
demonstrated
the
particulate
nature
of
heredity.
His
revolutionary ideas were
neither understood nor accepted until many years
after Mendel died.
孟德尔，众所周知
的遗传学之父，是一名修道士。当他还是大学生时就提出了物质的粒
子属性。孟德尔进行
了一系列周密安排的实验来证实遗传的颗粒性。直到他去世后，他的
理论才被理解和接受
。
Mendel's Classic
Experiments
Mendel studied
genetics through plant-breeding experiments with
the garden pea, a plant
species that is
self-fertilizing and breeds true (each offspring
is identical to the parent in the trait
of interest).
To
test the blending theory, he focused his research
on seven distinct characters.
Each of these characters, such as seed
color and plant height, present only two, clear-
cut
possibilities.
He also recorded the type and number of
all progeny produced from each pair of
parent pea plants, and followed the
results of each cross for two generations.
25
生物专业英语
（
Bioengineering
English
）
< br>孟德尔通过豌豆实验研究遗传学，豌豆是自花授粉植物和纯品系。为验证融合理论，他
的研究主要集中在
7
个特征上。例如，种子颜色，植株高度
，这些特征只有两个明确的可
能性。他记录了产生的每一个子代类型和数量，在杂交产生
子
2
代。
For each of the characters he studied,
Mendel found that one trait was
dominant
while the
other was
recessive.
In the second
filial
(F
2
) generation,
the ratio of dominant to recessive was
3:1.
Mendel
deduced
that
this
result
was
possible
only
if
each
individual
possesses
only
two
hereditary
units,
one
from
each
parent.
The
units
Mendel
hypothesized
are
today
known
as
alleles,
alternative
forms
of
genes.
Genes
are
the
basic
units
of
heredity.
An
organism
that
inherits identical alleles for a trait
from each parent is said to be
homozygous
for that trait;
if
different
alleles
for
a
trait
are
inherited,
the
organism
is
heterozygous
for
that
trait.
When
an
organism
is
heterozygous
for
a
trait,
the
resulting
phenotype
for
that
trait
expresses
only
the
dominant , the
organism
’s
phenotype
< br>—
its
physical
appearance and properties-differs
from
its
genotype,
which
may
include
both
a
dominant
and
a
recessive
allele.
A
pictorial
representation of
all possible combinations of a genetic cross is
known as a
Punnett square.
<
/p>
对于每个特征而言，要么显形，要么隐性。在子
2
代中显形与隐性比为
3
∶
1<
/p>
。只有在每
个个体仅拥有两个研究遗传单元，并每个单元来自一个
亲代时，实验结果才成立。此遗传
单元就是今天共识的等位基因。两个一样的等位基因决
定一个特征，称纯合。相反，称杂
合。当生物是杂合时，它的表型由显性基因决定。因此
，生物的表型与基因型是不同的。
旁纳特方格可以陈列所有可能的遗传组合。
The results of Mendel's
experiments on dominant and recessive inheritance
let to Mendel's
first law: the
law of segregation.
This law
states that for a given trait an organism inherits
one
allele from each parent.
Together these alleles form
the allele pair. When gametes are formed
during
meiosis,
the
two
alleles
become
separated
(halving
of
chromosome
number).To
gain
evidence for his theory
Mendel performed
test crosses,
mating plants of unknown genotype to
plants
that
were
homozygous
recessive
for
the
trait
of
interest.
The
ratio
of
dominant
26
生物专业英语
（
Bioengineering
English
）
phenotypes (if any) in the progeny
makes clear whether the unknown genotype is
heterozygous,
homozygous dominant, or
homozygous recessive.
分离定律，生物只遗传父母本等位基因对的一个等位基因。减
数分裂期形成配子时两
个等位基因分离。为验证此理论，他做了测交实验，即基因型未知
的植物与纯合的隐性基
因植物杂交。子代显性表型可以明确测得杂合基因或纯合基因的基
因型。
Mendel's Ideas and the
Law of independent Assortment
Mendel
also performed
dihybrid crosses,
which enabled him to consider how two
traits are
inherited relative to one
another.
This work let to
the
law of independent assortment,
which
states that the
alleles of genes governing different characters
are inherited independently.
An
apparent
exception
to
Mendel's
laws
is
incomplete
dominance,
a
phenomenon
in
which
offspring
of
a
cross
exhibit
a
phenotype
that
is
intermediate
between
those
of
the
parents.
However, incomplete dominance reflects
the fact that both alleles for the trait in
question exert
an effect on the
phenotype.
The alleles
themselves remain separate.
双因子杂合试验，
两个特征是如何相互影响遗传的。
试验结果
产生独自分配定律，
即等
位基因独立遗传。特例是，不完全显性
。子代的表型是父母本的中间类型。不完全显性说
明了两个等位基因对表型都有影响。，
等位基因会继续分离。
Mendel presented
his ideas in 1866 in a scientific paper published
by the Brunn Society for
Natural
History.
Unfortunately,
the
meaning
of
his
research
was
not
understood
by
other
scientists of the day.
His work was rediscovered
in 1900 by Carl Correns and Hugo de Vries.
1866
年，孟德尔在自然史上发表了他的科学论文，陈诉了他的观点。不幸的是，他的研
究不被
当时科学家接受。在
1900
年，他的著作再被发现利用。
Chromosomes and Mendelian
Genetics
Soon after Mendel's
work was rediscovered, Walter Sutton and Theodor
Boveri independently
proposed
that
the
hereditary
units
might
be
located
on
chromosomes.
Experiments
to
prove
this
hypothesis
were
carried
out
by
Thomas
Hunt
Morgan
and
his
students
at
Columbia
27
生物专业英语
（
Bioengineering
English
）
University, in research on the sex
chromosomes of fruit flies.
Morgan's studies were also the
first exploration of sex-linked traits.
It also led to the
discovery in 1916 by Calvin Bridges of
the
phenomenon
of
nondisjunction,
in
which
a
chromosome
pair
fails
to
segregate
during
meiosis.
孟德尔著作被再发现不久，
Walter
Sutton
和
Theodor <
/p>
Boveri
提出，遗传单位可能定位在
染色体组上。伴性遗传又导致了不分离现象的发现，即在减数分裂中，染色体对不分离。
课后作业
：第一篇阅读材料
答案
：
1C,2C,3A,4A,5B,6B
Glossary
pangenesis
泛生论，泛生说
The
theory
of
heredity
postulating
that
germs,
humours,
or
essences
migrate
from
individual
body
cells
to
the
sex
organs
and
contribute to the
gametes.
germ plasm theory
种质学说
A
substance
thought
to
be
transmitted
in
the
gametes
(germ
cells)
in
an
unchanged
form
from
generation
to
generation.
The
germ plasm was believed
to be unaffected by
28
生物专业英语
（
Bioengineering
English
）
the environment and to give rise to the
body
cells.
dominant
显性
The member of a pair of alleles that
shows
its effect in the phenotype
whatever other
allele is present.
recessive
隐形的
The member of a pair of alleles that
does
not show its effect in the
presence of any
other allelic partner.
allele
等位基因
Alternative
forms
of
a
gene
for
a
particular
characteristic
(e.g.,
attached
earlobe
genes
and
free
earlobe
genes
are
alternative alleles for ear shape).
gene
基因
A unit of heredity located on a
chromosome
and
composed
a
sequence
of
DNA
nucleotides.
homozygous
纯合的
A
diploid
organism
that
has
two
identical
alleles for particular characteristic.
heterozygous
杂合的
A
diploid
organism
that
has
two
different
alletic
forms
of
a
particular
gene.
Genotype
基因型
The
catalog
of
genes
of
an
organism,
whether or not these genes are
expressed.
phenotype
表型
The physical,
chemical, and psychological
expression
of
genes
possessed
by
an
organism.
Punnett square
旁纳特方格
A
method
used
to
determine
the
probabilities of combination in a
zygote.
law of segregation
分裂定律
When
gametes
are
formed
by
a
diploid
organism,
the
alleles
that
control
a
trait
separate
from
one
another
into
different
gametes, retaining
their individuality.
test cross
测交
A
cross
between
a
heterozygote
of
unknown
genotype
and
an
individual
homozygous
for
the
recessive
genes
in
question
.
dihybrid cross
双因子杂种，
双因子杂合子
A cross between individuals
that differ
with respect to two
specified gene pairs.
law
29
生物专业英语
（
Bioengineering
English
）
of independent assortment
独立分配定律，
自由组合定律
Members
of
one
gene
pair
will
separate
from
each
other
independently
of
the
members of other gene
pairs.
incomplete dominance
不完全显性
The
condition
in
which
two
allelic
genes
have a different
effect when they are together
as a
heterozygote in a diploid cell than either
of them have in the homozygous
state
nondisjunction
不分离
The
failure
of
separation
of
paired
chromosomes
at
metaphase,
resulting
in
one
daughter
receiving
both
and
the
other
daughter
cell
none
of
the
chromosomes
in
question.
Nondisjunction
can
occur
during
a
meiotic or mitotic division.
Lesson Fiv
e
（
2
学时）
Discovering the
Chemical
Nature of the
Gene
Genes Code
for Particular Proteins
The
first scientist to investigate the question of how
genes affect phenotype was Sir Archibald
Garrod,
whose
studies
of
alkaptonuria
implied
a
relationship
between
genes
and
enzymes.
Thirty
years
later
Beadle
and
Ephrussi
showed
a
relationship
between
particular
genes
and
biosynthetic
reactions
responsible
for
eye
color
in
fruit
flies.
Next,
in
a
series
of
classic
experiments on the effects of mutations
in the bread mold
Neurospora crassa,
Beadle and Tatum
explored
the
one-gene-one-
enzyme
hypothesis-
the
idea
that
each
gene
codes
for
a
particular
enzyme.
Their
work paved the way for other researchers to
elucidate the precise ways in which
enzymes affect complex metabolic 1949,
in research on the role of hemoglobin in
sickle
cell
anemia,
Linus
Pauling
helped
refine
the
one-
gene-one-enzyme
hypothesis
into
the
one-
gene-one-polypeptide hypothesis.
Archibald Garro
d
是第一个研究基因是如何影响表型的科学家，
他对尿黑酸症的
研究揭示
了基因与酶之间的关系。
Beadle
和
Ephrussi
在三十年后对果蝇眼睛颜色的研
究发现特殊基
30
生物专业英语<
/p>
（
Bioengineering
English
）
< br>因与相关反应的生物合成有关。接着对面包发霉粗糙脉孢菌的突变试验得出一个基因一个
< br>酶的假说。他们的工作为其他工作者铺平了道路，即精确地阐明了酶影响了复杂的新陈代
< br>谢途径。在
1949
年，对镰刀状细胞贫血症的研究对一
个基因一个酶的假说进一步上升为一
个基因一个多肽。
The Search for the Chemistry and
Molecular Structure of nucleic Acids
Nuclei
acid,
originally
isolated
by
Johann
Miescher
in
1871,
was
identified
as
a
prime
constituent of chromosomes through the
use of the red-staining method developed by
Feulgen in
the
early
1900s.
Frederick
Griffith's
experiments
with
the
R
and
S
stains
of
pneumococci
showed that an as yet unknown material
from one set of bacterial could alter the physical
traits
of
a
second
set.
In
the
1940s
the
team
of
Avery,
MacLeod,
and
McCarty
showed
that
this
unknown
material
was
DNA.
At
about
the
same
time
P.A.
Levene
discovered
that
DNA
contained
four
nitrogenous
bases,
each
of
which
was
attached
to
a
sugar
molecule
and
a
phosphate
group-a combination Levene termed a
nucleotide.
在
1871
年，核酸最初是由
Johann Miescher
分离成功，并由
Feulgen
在
1900
年证实核酸是染
色体组最基本的组成。
Frederick Griffith
对粗糙和光滑的肺炎球菌实验
表明，
不确定的某种
物质可以从一组细菌转移到另一种细菌中。
在
1940
年，确认该物质为
DNA<
/p>
。四个碱基和磷
酸分子分别连接在糖分子上，称核苷酸。
Disagreement over whether DNA
could carry complex genetic information was ended
in the
early 1950s by Martha Chase and
Alfred Hershey, whose work with
E. coli
showed clearly that
DNA, and
not protein, is the bearer of genetic information.
直到
1950
年，通过对大肠杆菌实验
发现，遗传物质是
DNA
，而不是蛋白质。
Each
DNA
nucleotide
contains
a
five-carbon
sugar,
deoxyribose,
attached
to
one
of
four
bases:
adenine,
guanine,
cytosine,
or
thymine.
Adenine
and
guanine
molecules
are
double-ring
structures
called
purines,
while
cytosine
and
thymine
are
single-ring
structures
called
pyrimidines.
The molecule made up of a
base plus a sugar is termed a
nucleoside.
In
31
生物专业英语
（
Bioengineering
English
）
each molecule of DNA a phosphate group
links the five-carbon sugar of one nucleoside to
the
five-carbon
sugar
of
the
next
nucleoside
in
the
chain.
This
phosphate
bonding
creates
a
sugar-
phosphate backbone.
每个核苷酸都含有一个五碳脱氧核糖，分别
连接
4
个碱基，即：腺嘌呤，鸟嘌呤，胞嘧
啶，胸腺嘧啶。碱基连接糖称核苷。磷酸键形成磷酸骨架。
Chargaff’s
rules
describe
the
fact
that
(1)
the
amount
of
adenine
is
equal
to
the
amount
of
thymine in DNA, with amount of cytosine
equal to that of guanine, and (2) the ratios of A
to T
and of C to G vary with different
species.
（
1
）腺嘌呤与胸腺嘧啶，胞嘧啶与鸟嘌呤相等；（
2
）腺嘌呤与胸腺嘧啶，胞嘧啶与鸟
嘌呤的比例随物种不同而不
同。
The Research Race for the
Molecular Structure of DNA
In the late
1940s and early
1950s, researchers
looking for the structure of DNA drew upon
Chargaff s insight, Levene's ideas on
DNA components, and two other lines of evidence.
One
was the
suggestion of Linus Pauling that DNA might have a
helical structure held in place by
hydrogen
bonds,
and
the
other
was
X-ray
diffraction
photos
of
DNA,
showing
a
helical
structure with distance between the
coils, taken by Franklin and Wilkins.
直
到
40
年代末
50
年代初，研究者在寻求
DNA
结构过程中，确立了
Chargaff
的观点和
,
Levene
的组成理论以及其他两个线索。一个是
Linus
Pauling
的假设，
DNA
可能具有螺旋结
构，通过氢键连接。另一个是
X-
衍射图片，
Franklin and
Wilkins
提供。
Based
on
this
information
Watson
and
Crick
proposed
the
double
helix
model
of
DNA-A
twisted
ladder-like
molecule
with
two
outer
sugar
phosphate
chains
and
rungs
formed
by
nucleotide
pairs.
Paired
nucleotides,
which
always
occur
as
A-T
or
G-C,
are
linked
by
hydrogen bonds.
Watson and Crick also proposed that
genetic information is encoded by the
sequence of base pairs along the DNA
molecule.
32
生物专
业英语
（
Bioengineering
English
）
基于这些信息，
Watson
和
Crick
提出了双螺旋结构模型，成对的核苷酸通过氢键相连，
遗传信息就贮藏在碱基对中。<
/p>
How DNA
Replicates
In
their
model
of
DNA
structure
and
function,
Watson
and
Crick
hypothesized
that
DNA
replicates
itself
by
along
the
hydrogen
bonds
joining
A
to
T
and
C
to
G.
This
process
would
produce
two
opposite
halves
that
could
then
serve
as
templates
for
the
construction
of
new,
complementary
strands.
This
model
of
semiconservative
replication
conservative because each new molecule
has one half of the former parent molecule-was
later
confirmed by the work of
< br>DNA
进行复制是以拉链方式自我复制，
产生的两个二分
体分别为模板生成互补链，
即半
保留复制。并由
Meselson
和
Stahl
验证。
In
E. coli
DNA
replication begins with the formation of a
bubblelike structure on the circular
chromosome that is produced by
replication forks.
Studies of bacterial DNA replication
have
shown that
a
growing DNA chain lengthens only in the
5' to 3' direction (from the 5' carbon of
one sugar to the 3' carbon of the
next).
The leading strand
is synthesized continuously, while
the
lagging strand is synthesized in short stretches
known as
Okazaki fragments.
The enzyme
DNA polymerase
links free nucleotides as they line up
on the template formed by the original
strand of the parent molecule.
33
生物专业英语
（
Bioengineering
English
）
In eukaryotes DNA replication follows
the same general principles as in prokarotes. On
the
long
DNA
molecules
replication
proceeds
(in
two
directions
at
once)
from
hundreds
or
thousands of points of origin.
< br>大肠杆菌复制开始时形成泡样复制叉，链生长方向由
5
′
向
3
′端，前导链连续生成，后
随链由
冈崎片段组成，由
DNA
聚合酶催化。真核生物复制与原核生物
复制相似，但有几百
到几千个复制原点（原核一般只有一个复制原点）。
Glossary
one-gene-one-enzyme
hypothesis
一基因一
酶假说
The hypothesis that a large class of
gene exist
in which each gene controls
the synthesis or
activity
of
but
a
single
enzyme.
Since
enzymes and other
proteins whose syntheses
are controlled
by more than one gene are now
known,
this hypothesis has been replaced by
the one-gene-one polypeptide
hypothesis.
one-gene-one-
polypeptide
hypothesis
一
基
因一多肽假说
34
生物专业英语
（
Bioengineering
English
）
The hypothesis that a large class of
genes
exist in which each gene controls
the
synthesis of a single polypeptide.
The
polypeptide
may function independently or as
a
subunit of a more complex protein.
adenine
腺嘌呤
A purine base that is an essential
constituent
of
the
nucleic
acids
and
also
of
such
coenzymes as NAD and FAD.
guanine
鸟嘌呤
A
double-ring
nitrogenous
base
molecule
in
DNA
and
RNA.
It
is
the
complementary
base of
cytosine.
cytosine
胞嘧啶
A
single-ring
nitrogenous
base
molecule
in
Note
that
thymidine
is
a
deoxyriboside
and
DNA
and
RNA.
It
is
complementary
to
cytidine,
uridine,
adenosine,and
guanosine
guanine.
thymine
胸腺嘧啶
A single-ring nitrogenous base molecule
of
A technique for determining the
arrangement
DNA but not RNA.
It is complementary to
of
atoms
in
a
crystalline
substance
by
adenine.
analysing
the
diffraction
patterns
produced
purine
嘌呤
One of a group of nitrogenous bases
whose
parent compound has the formula
shown.
when
a
narrow
beam
of
X-rays
is
passed
through
the
substance.
X-ray
diffraction
has
contributed
to
the
elucidation
of
structure
of
35
The two most abundant
purines are adenine
and guanine, which
are constituents of
nucleic acids and
coenzymes.
pyrimidine
嘧啶
A
heterocyclic
organic
compound,
C
4
N
4
N
2
the
fundamental
form
of
pyrimidine
bases.
Some
of
these
bases
are
constituents
of
nucleic acid.
nucleoside
核苷
A
purine
or
pyrimidine
base
attached
to
ribose
or
deoxyribose.
The
nucleosides
commonly
found
in
DNA
and
RNA
are:
cytidine,
cytosine
deoxyriboside,
thymidine,
uridine,
adenosine,
adenine
deoxyriboside,
guanosine,
and
guanine
deoxyriboside.
are ribosides.
X-ray
diffraction
X
射线衍射
生物专业英语
（
Bioengineering
English
）
many
biological
molecules,
including
some
important
macromolecules,
e.g.,
DNA,
haemoglobin, myoglobin.
DNA double helix
双螺旋
The
three-dimensional
structure
of
A
point
at
which
the
two
strands
of
a
DNA
double
helix
are
unwound
and
separated
during replication.
Okazaki
fragment
冈琦片断
A short sequence of DNA that is the
primary
product
of
DNA
polymerase
during
DNA
replication.
polymerase
DNA
聚合酶
An
enzyme
that
brings
new
DNA
triphosphate
nucleotides
into
position
for
bonding on another DNA molecule.
doublestranded DNA.
semiconservative replication
半保留复制
The method
of replication of DNA in which
the
molecule divides longitudinally, each half
being conserved and acting as a
template for
the formation of a new
strand.
replication fork
复制叉
Lesson Six
（
2
学时）
The
Origin and
Diversity of Life
A Home for Life: Formation
of the Solar System and Planet Earth
The story of life's origins begins with
the formation of the earth.
The sequence of events
that
gave rise to our planet began, in turn, with the
cosmic explosion physicists call the
Big
Bang.
The sun at the center of our solar
system condensed from a cloud of primordial matter
roughly 5 billion years ago; the
planets, including the earth, condensed about 4.6
billion years
ago.
The earth is composed of a number of
layers: a solid
crust,
a
semisolid
mantle,
and a
largely molten (liquid)
core
that has a solid center.
Basic physical features of Earth that
may
have made the emergence of life
possible include the planet's size, temperature,
composition,
36
生物专业英语
（
Bioengineering
English
）
and distance from the sun.
The major current hypothesis holds that
life arose spontaneously
on the early
earth by means of
chemical
evolution from nonliving substances.
生命起源于地球的形成。大爆炸是
我们行星形成的开始。太阳在
50
亿年前生成，位于
太阳系中心，行星，包括地球，在
46
亿年前生成
。地球由多层组成：坚硬的地壳，半流体
的地幔，一个很大的溶解中心中存在一个坚实的
中心。地球的基本特征使生命起源成为可
能，包括行星的大小，温度，组成以及离太阳的
距离。当前主要假设认为，由非生命的化
学物质进化过程自发产生了生命。
The Emergence of life: Organic
and Biological Molecules on a Primitive
Planet
Evidence for prelife
stages of chemical organization comes from
laboratory experiments that
try
to
duplicate
the
physical
environment
and
chemical
resources
of
the
early
earth.
These
experiments,
including
the
pioneering
work
of
Miller
and
Urey,
have
successfully
produced
organic
monomers
including
amino
acids,
simple
sugars,
and
nucleic
acid
bases.
The
probable next step toward life was the
spontaneous linking of such monomers into polymers
such
as
proteinoids
and
nuclei
acids.
Current
research
suggests
that
likely
sites
for
this
polymerization were
clay or rock surfaces.
通过创造出地球早期的自然条件和化
学资源条件，科学家在实验室中已经获得了化学
有机体生命前阶段的证据。
这些实验包括米勒等早期所做工作，
成功地产出了有机单体，
包括氨基酸，单糖，核酸碱基。这些单体自发的连接成多聚体，如类蛋白和核酸，使进
< br>入生命状态成为可能。这些聚合作用可能发生在泥土或岩石表面。
Researchers have found that, when
energy is available to a system, they can generate
three
kinds of organic molecular
aggregates.
The Russian
Aleksandr Oparin obtained polymer-rich
droplets,
called
coacervates
from
solutions
of
polymers.
Sidney
Fox
generated
proteinoid
microspheres
from
mixtures
of
amino
acids
and
water.
A
third
laboratory
structure
is
the
liposome,
a spherical lipid
bilayer that forms from phospholipids.
A structure similar to one
or more of these aggregates may have
been the precursor of true cells.
37
生物专业英语
（
Bioengineering
English
）
< br>当一个系统获得能量时，
可能发生
3
种有机分子的聚集。
从多聚物的溶液中俄国科学家
获得了富
含小液滴的多聚物，
即凝聚物。
从氨基酸和水的混合液中
Fox
获得了类蛋白微球
体。实验室第三个结
构物质是脂质体，即由磷脂形成的球形脂双层结构。
Further steps in the appearance of
cells on the earth included the development of RNA
and
DNA
as
biological
information
molecules.
Evidence
suggests
that
RNA,
which
can
form
spontaneously under conditions
mimicking those of the early earth, was the first
informational
molecule.
The
discovery
of
RNA
ribozymes-RNA
that
can
act
as
an
enzymelike
catalyst
suggests
that
such
catalytic
RNA
also
could
have
assembled
new
RNAs
from
early
nucleotides.
Certain catalytic RNAs can also carry
out sexlike exchanges of pieces of RNA.
RNA
可能是地球早期形成的第一个贮藏信息的物质。在实验室模拟早期地球自然条件
下其可自发形成。核酶的发现说明它可以催化早期核酸形成新的
RNA
。对于
RNA
物种而
言，某些催化
RNA
具备类似于性交换的功能。<
/p>
Following the development of
a lipid-protein surface layer and replicating RNA
and DNA
informational
molecules,
the
events
leading
to
the
emergence
of
living
cells
would
have
included
the
origin
of
the
genetic
code;
the
sequestering
of
RNA
or
DNA
into
cell-like
structures; and the development of
metabolic pathways.
接下来脂蛋白表层的形成，
RNA<
/p>
的复制
,DNA
信息分子的形成，
最终导致活细胞的出现，
包括最初的遗传密码，
RNA
或
DNA
被包裹进细胞样的结
构中；及代谢途径的建立。
The Earliest
Cells
The oldest fossils
that may represent living cells are found in rocks
that are about 3.5 billion
years old.
The cells were probably
anaerobic heterotrophs, with autotrophs arising
much later.
The first
autotrophs produced their own nutrients and
released O,-a metabolic by-product that
had a crucial impact on later life
forms.
The resulting
ozone layer
in the earth's
atmosphere
reduced the penetration of
ultraviolet light.
As a
result, cells would survive in shallow water
and
on
the
land
surface.
The
increasing
quantity
of
atmospheric
oxygen
also
permitted
the
38
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