唇膏英文生物专业英语第三版蒋悟生编__课文翻译

2021年1月20日发(作者：tyrannosaurus)

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. < br>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
m RNA
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）

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,
that
sequence
into
protein.

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.
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
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.
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。

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。

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
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 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。< br>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
稳固

to
cells,
its microtubules
英
[
?
maikr
?u?tju:bju:l
]


and filaments
丝状物

and their
associated proteins enable cells to move by creeping
爬行

or
gliding
滑动
.

Such movements require a solid
固体的

substrate
to which the cell can adhere
附着

and can be guided by the
geometry
d
?i??
mitri
]


几何形状
of the surface.

Some cells also
exhibit
[
i
ɡ?zibit
]

展览

chemotaxis,
kem
??
t?
ksis
趋药性

the
ability to move toward or away from the source of a diffusing
扩
散

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
[
?
sili
?
]
纤毛
or
flagella

英
[
fl
??
d
?< br>el
?
鞭毛
.
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
基体
is located.
Movement is based on the activities of tiny dynein
动力蛋白

side
arms that extend from one of the microtubules of each doublet
成
对的东西
.

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
?
mai
?
usin
肌凝蛋白

proteins attached to organelles
细
胞器
,
小器官

push against microfilaments arrayed
[
??
rei
]

展示
throughout the cell. Microfilaments and microtubules are
responsible for almost all major

cytoplasmic movements. During
cell division, microtubules of the spindle assembled
集合
,
收集

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

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 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

Numerous
short,
hairlike
structures
projecting
from
the
cell
surface that enable locomotion.

flagella





鞭毛

(
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.

Photosynthesis


Photosynthesis
occurs only in the chlorophyllchlorophyll
叶绿
素
-containing
cells
of
green
plants,
algae
藻
, and
certain
protists
原生生物
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
然而

cellular
细胞的

respiration
呼吸
is
highly
exergonic
吸收能量的

and
releases
energy,
photosynthesis
光合作用

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。

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
裂
开

(oxidized),
0
2
is
released,
and
ATP
and
NADPH
are
formed.

These reactions must take place
in the presence of

在面前

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，
A TP
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
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
色素
for
the
lightdependent
reactions
are
embedded
深入的

内含的
in
the
thylakoid
类囊体

membrane
膜

隔膜

of chloroplasts
叶绿体
.

The dark reactions take place
in the stroma.
基质



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，
P680
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。< br>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
NADP H
。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
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.


大部分植物是碳
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。



课后作业
：第一篇阅读材料

答案
：
1B,2A,3A,4D,5C,6c
























Glossar
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 giving a
continuous spectrum is passed through a substance.
Calvin-Benson cycle

卡尔文·本森循环

Cyclic reactions that are the
light-independent reactions of photosynthesis.

In land
plants, RUBP, or some other compound to which carbon
has

been affixed, under goes rearrangements that lead to
formation of a sugar phosphate and to 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

A
plant
in
which
the
light-independent
reactions
of
photosynthesis
start
with
a
threecarbon
compound.

Most plants are C
3
plants.

C
4
plant
四碳植物

A
plant
such
as
corn
in
which
the
light
independent
reactions
of
photosynthesis
star
with
a
four-carbon
compound.

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
membranes.

Photosystem
I
operates
during
the
cyclic
pathway;
photosystem
Ⅱ

operates during both the cyclic and noncyclic 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.




























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
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；
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。





Mitosis: Partitioning the Hereditary Material

Biologists divide the mitotic cycle into four phases.

At the
beginning
of
prophase
前期

the
chromosomes
each
consist
of
two
highly
condensed
chromatids
attached
to
each
other
at
a
centromere.

As
prophase
ends
and
metaphase
中期

begins,
the condensed
浓缩的

chromosomes become associated with the
spindle
纺锤体
.

Eventually the chromosomes become arranged
in
a
plane
(called
the
metaphase
plate)
at
a
right
angle
to
the
spindle
fibers.

Next,
during
anaphase
后期
,
the
two

sister
chromatids of each chromosome split, and one from each pair is
drawn
toward
each
pole
of
the
cell.

During
telophase
末期

nuclear
envelopes
包
膜

begin
to
form
around
each
set
of
chromosomes, and division of the cytoplasm takes place.
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

染色
单体

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
着丝粒
fibers,
extend
outward
from
the
spindle
poles
to
structures
on
the
chromosomes called kinetochores
着丝粒
.

During anaphase the
fibers begin to shorten, and the chromatids begin to move apart.
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
中心粒
, while in plant and
fungal
真菌

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
细胞浆移动
.

In animal cells it takes place as
a
ring
of
actin
filaments
contracts
使缩短

合同契约

around
the
cell equator
赤道
, pinching
收聚

the cell in two.

In plant cells,
which are bounded
有限制的

by a cell wall, cytokinesis involves
the
building
of
a
new
cell
plate
across
the
dividing
cell
at
its
equator.

Cell
wall
material
is
then
deposited
存放堆积

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
减数

is a special form of cell division that takes place
in
the
reproductive
生殖

organs
that
produce
sex
cells.

Like
mitosis,
it
takes
place
after
DNA
replication
has
occurred
and
involves two sequential
连续的

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
因此
,
the
homologous
同源的

chromosomes
distributed
分布

to
different
progeny
后裔

cells are not identical
同样的
.
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
同源

chromosomes undergo
经历
sy-napsis
联会

, or pairing, which is
brought about by a bridging structure of proteins and RNA called
the
synaptonemal
联会丝的

complex.

The
homologous
pairs
stay
together
when
they
align
排列

on
the
metaphase
中

plate.

Unlike
the
anaphase
of
mitosis,
however,
during
anaphase
I
the
two chromatids of each chromosome stay joined at the centromere
着丝点

and move together to one of the two poles of the cell.

It
is
this
event
that
results
in
the
halving
减
半
的

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。
During
telophase
末
期

I
nuclear
envelopes
enclose
the
chromosomes
in
nuclei,
and
in
most
species
cytokinesis
细胞浆
流动

(the
first
nuclear
division)
follows.

The
second
nuclear
division begins with metaphase
Ⅱ
, in which the chromosomes in
each
daughter
cell
again
align
排列
on
a
metaphase
plate.

The
centromeres
着丝粒

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
分别
,
make
simple
cell
division
and
sexual
reproduction
possible.

Each
means
of
passing
on
hereditary
遗传

information
has
advantages.

In
asexual

无性的

reproduction the parent organism
生物体

gives
rise to offspring
后代
that are genetic clones of the parent.

The
advantages
of
this
type
of
reproduction
are
that
it
preserves
the
parent's
successful
genetic
complement
遗传互补
,
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
灾难的

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
机制

for
the
elimination
of
deleterious
mutations.

It
also
allows

gene
forms
to
arise
and
spread
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。

课后作业
：第一篇阅读材料

答案
：
1C,2B,3D,4B,5A,6D

Glossary
mitosis
有丝分裂

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.
chromatin
染色质

The material of which the chromosomes are composed.

DNA
and protein are the 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 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 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
cytokinesis
胞质分裂

one cell into two new cells.
cell plate

细胞板

A plant cell structure that begins to form in the center of the cell
and proceeds to the cell membrane, resulting in cytokinesis.

Foundations of Genetics



Early Theories of inheritanee

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
exposed
to
theories
of
the
particulate
nature
of
matter
while
a
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.
< br>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。< br>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.
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
—
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.

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
。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 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
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 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 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
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