短裙英文生物专业英语第三版蒋悟生课文翻译精华整理

2021年1月20日发(作者：拖车费英文)

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
t..
of
the
cytoskeleton.
Dissolved
inluid 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
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，为染色体上遗
传物质（
DNA
）提供空间（原核生物遗传物质存在于拟核中）
。细胞核含有一或二个核仁，
在细胞分裂中发挥作用。
一个穿孔的囊叫核膜，
将细胞核和其中含物与细胞质分开，
小分子
物质可以自由通过核膜，但大分子物质如
m RNA
和核糖体必须通过核孔进出核膜。

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，每种细胞器在细胞中行使一项专门功能。本
节主要介绍核糖体、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,

the
genetic
sequence
coded
in
it
and
translating
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.
细胞中核糖体的数量变化从几百到几千，
核糖 体数量如此之多反映了核糖体是氨基酸组装成
蛋白质并被运出或在细胞过程中使用的位点这样一个事实。
完整的核糖体由大亚基和小亚基
组成。在蛋白质合成中两个亚基沿
mRNA
链移动，阅读其中编码的遗传序列，将序列翻译
成蛋白质。一条
mRNA
上可能有多个 核糖体，这种组合称多聚核糖体。大多数细胞中的蛋
白质由细胞质中的核糖体
（游离核糖体）< br>制造。
运输蛋白和膜蛋白通常由附着于质网上的核
糖体制造。


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.
质网是由 膜状囊、管和小泡等排列在一起，有粗面质网和滑面质网两种类
型。
两种类型都与蛋白质的合成 和运输有关。
粗面质网上散布着多聚核糖体，
似乎也是细胞
分裂后形成核膜的来源。< br>
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.
光滑质网上无核糖体
/
光滑质网上缺乏多聚核糖体，主要 作用是脂肪和类固醇的合成
以及细胞有毒物质的氧化。两种质网合成的产物在其中进行分流或运输到细胞 外
/
这两种类
型的质网都担当细胞中的隔断，致使特殊产物能够分离并最终逃避到细胞 外的特定区域。

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 和可溶性分子。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（颗粒物的吸收）和胞饮作用。












A subset of vacuoles are the organelles known as lysosomes, which contain digestive e(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
（在高尔 基体中的溶酶体中包装而成）
，能够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
/
行使消化食物颗粒和分解损坏的细胞组件的作用。

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.
线粒体是所有细胞中发生产
能化学反应的 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

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、蛋白质和油类的
贮存场所；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。
叶绿体的部结构是由多层膜垛叠形成的叶绿体基粒，其中包埋 在基质中的基粒称子座。

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 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.
所有的真核细胞都有细胞骨架，它是由细丝和


管组 成的回旋状的网格，似乎充满了细胞中的所有空间并为其它各种细胞器提供了支撑作
用。
细胞骨 架大部分由线状的微丝组成，
微丝主要由可收缩的肌动蛋白组成。
动物和植物细
胞中多 种类型的细胞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组分是微管，
由球形蛋白质
—
微管蛋白组成，< br>象脚手架那样
使细胞维持稳定的形状。
细胞骨架的中间丝提供了细胞质伸缩动力。
一些动力酶如，
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。

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。某些细胞具备趋化性，
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.
某些真核细胞能在液体中自由运
动，由纤毛或鞭毛推动。纤毛和鞭毛具有同样的部结构：
9
个联管（微管对）排列成环状，< br>沿纤毛或鞭毛纵向延伸，
环中心是两个或两个以上微管组成。
纤毛或鞭毛从细胞表面的基 体
长出，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 chromos omes.
大部分
植物细胞的营养物质、
蛋白质和其它物质通过胞质流动进行运动。< br>这个过程是由于依附在细
胞器上的肌球蛋白推动微丝在细胞中重排形成的。绝大部分细胞质运动由 微丝和微管完成。
在细胞分裂过程中，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。

Photosynthesis occurs only in the chlorophyllchlorophyll-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 发生在绿色
植物，
海藻，某些原生动物和细菌等含有叶绿素的细胞中。总体来说，
这是 一个将光能转化
成化学能，
并将能量贮存在化学键中。
从化学和能量学的角度来看，< br>它是细胞呼吸作用的对
立面。细胞呼吸作用是高度放能的，而光合作用是需要能量并高吸能的过程 。

Photosynthesis starts with CO2 and H2O 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), 02 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,
CO2
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。
第一步反应称为光反应，
水分子分解
（氧化）
，
放出氧气，< br>形成
ATP
和
NADPH
。这些反应必须有光能的存在才能进行。第二 步称为非光依赖型反应（暗反应）
，
二氧化碳被还原
（通过加氢）
成碳水化合 物，
这步反应依赖于第一步反应产生的
NADPH
和
ATP
作为电子载体

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. < br>以上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。

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
abt
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
to other molecules and stored as chemical energy.
生物分子能捕获可见光谱中的光能用于建设< br>性的工作。
植物细胞中叶绿素在不同光波下吸收特定吸收光谱。
当光线被吸收时，
光的作用
使分子中的电子发生重排
/
它改变了吸收分子的电子排列。由光子增加的能 量推进分子的能
量状况从稳定状态（基态）转变为不稳定的激发态。在光合作用的光反应过程中，
吸收分子
又回到基态，多余的激发能传递到其它分子中，以化学能的形式储存起来。


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
(P6 80).
所有的光合作用生物含有不同等级的叶绿素和一种或多种类胡萝卜素
（辅助色素），这些色素在光合作用中发挥作用。称作天线复合体的色素分子群存在于类囊
体中。
到达任 何一个色素分子的光能汇集到称为反应中心叶绿素的特殊的叶绿素分子上，
它
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 与
电子受体分子和电子供体分子相关联。
这些集合体就是大家熟识的光合系统Ⅰ
(P700)
和光合
系统Ⅱ
(P680)
。

The
photosystems
of
the
light- dependent
reactions
are
responsible
for
the
packaging
of
light
energy
in
the
chemical
compounds
A
TP
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A
TP
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。
/
这一包装过程从光< br>线到达光合系统
II
的活性中心
P680
这一步骤开始，包括了一系列 氧化还原反应反应。在第
一个步骤中，水分子被分解，放出氧气，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< br>ATP
。链的最终受体是光合系统
I
的
P700
活性中心。 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
。前面产生的
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
.
由光能激发产生的电子沿电子传递链
传递并产生
ATP
的过程称为光合磷酸化。电子通过光合系统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
，
在这一过程中一些电
子在 光合系统Ⅰ和Ⅱ之间的电子传递链中回流。

In the light- independent reactions of photosynthesis, which are driven by ATP and NADPH, C02
is
converted
to
carbohydrate.

The
reactions
are
also
known
as
the
Calvin-Benson
cycle.
Atmospheric
CO2,
is
fixed
as
it
reacts
with
ribulose
biphosphate
(RuBP),
a
reaction
that
is
catalyzed
by
the
enzyme
ribulose
biphosphate
carboxylThe
reduction
Of
C02
to
carbohydrate
(fructose
diphosphate
several
more
steps
of
the
cycle.
Finally,
RUBP
is
regenerated
so
that
the
cycle may continue.
由
ATP
和
NADPH< br>驱动的暗反应中，
CO2
转化成碳水化合物。即卡尔文
-
本森循环。在 二磷酸核酮糖羧化酶的催化下，二磷酸核酮糖固定空气中的
CO2
。
CO2
通 过
循环中的几步反应还原成为糖类（二磷酸果糖）
，最终核酮糖二磷酸再生，这样循环能够持< br>续进行。

High
levels
of
oxygen
in
plant
cells
can
disrupt
photosynthesis
and
can
also
cause
photorespiration-an inefficient fun of the dark reactions in which 02 is fixed rather than C02 and
no carbohydrate is produced.
植 物细胞中高浓度的氧气能够破坏光合作用，同时也能够引起光
呼吸，这是一种效率差的暗反应，

02
而不是
CO2
被固定，不产生糖类。


Most
plants
are
C3
plants;
they
experience
decreased
carbohydrate
production
under
hot,
dry
conditions as a result of the effects of photorespiration. Among C4 plants, however, special leaf
anatomy and a unique biochemical pathway enable the plant to thrive in and conditions. Thus C4
plants lessen photorespiration by carrying out photosynthesis only in cells that are insulated from
high levels of CO2. They also possess a novel mechanism for carbon fixation.
许多植物是
C3
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
C4
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。
这样C4
植物并非在细胞
中存在高浓度的
CO2
条件下才能进行光合作用， 这是碳固定的一个新机制。

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。这些螺旋或超
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。

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
sms
whose
cells
contain
two
sets
of
parental
chromosomes
are
called
diploid;
those
with
cells
containing a single set of parental chromosomes are called haploid.
以图示方式展示出来的螺旋
的、浓缩状态有机体染色体，称为染色体组型。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。
生物细胞含有两套亲本染色体的有机 体
称为二倍体；
含有单套染色体的有机体称单倍体。
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.
细胞周期是一 个有顺序的过程：细胞生长、准备分裂、分裂形成两个子细
胞，子细胞再循环。
此循环使得单细 胞生物永生。
多细胞生物中的许多细胞，包括动物肌肉
和神经细胞，能够使细胞周期时间延长或 完全脱离细胞周期。


The normal cell cycle consists of four phases.

The first three include G1, the period of normal
metabolism; S phase, during which normal synthesis of biological molecules continues, DNA is
replicated,
and
histones
are
synthesized;
and
G2,
a
brief
period
of
metabolism
and
additional
growth.

Toget G1, S, and G2 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 的细胞周期包括四步。
前
3
步包括
G1(
正常的代阶段
)< br>；
S
期（持续进行生物分子的正常合成，
DNA
复制，组蛋白合成）< br>；
G2
期（代和再次生长的短阶段）
。
G1
期、
S< br>期和
G2
期合起来称为间期。细胞周期的第四步为
M
期（进行有丝分 裂的阶段）
，在这一阶段，复制的染色体浓缩、运动，细胞分裂。被认为
是细胞质的特性和外部 的刺激因子和抑制剂例如抑素控制了细胞周期。

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 thein a plane (called the metaphase plate) at a rig 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.
生物学家将有丝< br>分裂划分为
4
个阶段。
分裂前期，
每一条染色体包括两条高度浓缩的染 色单体，
两个染色单
体通过着丝粒连接在一起。当前期结束时，分裂中期开始，浓缩的染色体与 纺锤体相连，最
后以与纺锤丝成垂直角度排列在赤道板上。
在分裂后期，
每个染色体上 的两个姊妹染色单体
分开，
分别移向细胞两极。在分裂末期，
围绕每一套染色体开始形 成核膜，
然后开始细胞质
的分裂。


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
micros
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.
在有丝分裂过程 中，是纺锤体的微管确保了染
色单体适时的以正确方向进行分离。
当微管从每个分裂细胞的两极 延伸至赤道板时，
形成了
纺锤体的一半。
在有丝分裂前期，
另外一种微管，< br>着丝粒纤维从纺锤体的两极向外延伸到染


色体的动粒上。在分裂后期，纤维开始缩短，染色单体开始分开。

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.
在植物和动物细胞中纺锤体的形成不同，动物细胞中，与中心体有关。在
植物和真菌细胞中纺锤 体的形成与叫做微管组织中心的区域有关。

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, pinchin the cell in two. In
plant cells, which are by a cell wall, cytokinesis involves the building of a new cell plate across
the dividing cel Cell wall material is then deposited in the region of the cell plate.
有丝分裂结束
时细胞质的分裂称为胞质分裂。
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。植物细胞有细胞壁包被，通过在赤道板形成 新的细胞板实现胞质分裂。

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 sequ
nuclear divisions (meiosis I and meiosis
Ⅱ
). These divisions result in four cells, each with half the
number of chromosomes of the parent cell. The phen of crossing over during meiosis results
in
exchanges
of
genetic
infon
between
chromosomes.
Hence,
the
homologous
chromosomes
distributed to different progeny cells are not identical.
减数分裂 是发生在产生生殖细胞的生殖器
官中的特殊的细胞分裂方式。如有丝分裂，它发生在
DNA复制后，包括两个有顺序的核分
裂阶段（减数分裂
I
期和减数分裂
II< br>期）
。这种分裂产生
4
个子细胞，每一个子细胞的染色
体数是母细胞染 色体数的一半。减数分裂交叉现象的出现导致了染色体之间互换遗传信息，
这样分配到不同后代细胞中的 同源的染色体并不相同。

As in mitosis two chromatids exist for each chromosome at the beginning of prophase 1. During
this phase the homologous chromosomes undergo sy-napsis, or pairing, which is brought about by
a bridging structure of proteins and RNA called the synaptonemal complex. The hom pairs stay
together
when
they
align
on
the
met
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.
象有丝分裂那样，
在分裂
前< br>I
期的开始，每个染色体含有两条染色单体。在这一阶段，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。当同源染色体对排列于赤道板上时，这两条染色体同时存在。然而，与有丝分裂后期不同的是，减数分裂后期
I
每个染色体的两条染色单体在着丝粒
处相连，
一起移向细胞的一极。
正是由于这一事件导致减数分裂中
4
个子细胞的染色体数目
减半。

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 d istributed.
在减数分裂末期
I
，
核被膜
将染色体包裹在 细胞核中，接着多数种类开始胞质分裂（第一次细胞核分裂）
。第二次细胞
核分裂开始于减数分 裂中期
II
，
每个子细胞中的染色体重新排列排列在赤道板上。
着丝粒最终分离，每个姊妹染色单体移向纺锤体的一极。接着胞质分裂。整产生
4
个单倍体细胞，亲
本的染色体被随机分配。


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 disadvant 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 variaby and a ready mec for the elimina of deleterious mutations. It also allows

有丝分类 和减数分裂分别使简单的细
胞分裂和有性生殖成为可能
,
每一种方式在传递遗传信息过 程中各有优势。无性生殖产生后
代时克隆
（完全复制）
了中亲本的遗传信息，
这种生殖类型的优点是它保存了亲本成功的遗
传信息，
基本或完全不需要特化出生殖器官，与有性生殖相比更迅速。
但一个简单灾难性事
件或疾病都可能摧毁一个细胞群体。
有性生殖的主要好处是它能够提供遗传的多样性，
具有
迅速的清除有害变异的机制。它也使新基 因形式出现、增加并扩展到整个种群。


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.
早期的遗传学思想包括希伯克拉底的泛生论和斯曼的种质理论。
在小鼠实验的基础上，
斯曼提出遗传信息储存在配子中并将遗传信息传递给后
代。
这些早期的观点合称为混合理论：
子代持有的可遗传性状是两个亲本性状的混合，
所以
在后代中每一个亲本失去了独特的性状

Gregor Mendel, an Augustinian monk in the monastery at Brunn, Austria, is known as the
of genetics.
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.
孟德尔是奥地利布鲁恩修道
院奥古斯丁教的修士，被誉为
“
遗传学之父
”
。当他还是大学生时就提出了物质的粒子属性，
同时还有数学的 背景。
他开展了一系列精心设计的实验，
证明遗传的物质本质。
他的革命性
的 思想直到他去世后许多年才被人理解与接受。

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
paia
plants,
and
followed the results of each cross for two generations.
孟德尔通过花园中的豌豆开展了植物育
种试验而研究遗传学，
豌豆是自花授粉植物和纯品系。< br>为验证融合理论，
他将研究重点放在
7
个明显的特征上。这些特征的每一个，例 如，种子颜色和植株高度，代表了仅有两个且易
于区分的可能性。他记录了产生的每一个子代的类型和数 量，以及两代杂交的结果。

For each of the characters he studied, Mendel found that one trait was dominant while the other
was
recessive.
In
the
second
filial
(F2)
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
ex
presses
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.< br>对于他研究的每一种特性，要么显性，要么隐性。
在子
2
代中显形与隐性比为< br>3
∶
1
。孟德尔推断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。
孟德尔假设的单位如今称为等位基因
（基因< br>二中选一的形式）
。基因是遗传的基本单位，一些有机体继承了来自父本、母本的同一性状
的两个相同的等位基因，
被称为某一性状的纯合体。
如果继承的是某一性状的不同的等位基< br>因，
有机体被称为某一性状的杂合体。
当有机体是某一性状的杂合体时，
它的表 型由显性基
因决定。因此，有机体的表型（它的物理形状和特性）与它的基因型不同，基因型同时包括< br>一个显性和一个隐性等位基因。遗传杂交的所有可能的组合的图示形式被称为庞纳特方格。


The results of Mendel's experiments on dominant and recessive inheritance let to Mendel's first
law: the law of 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
thMendel
performed
test
crosses,
mating
plants
of
unknown
genotype
to
plants
that
were
homozy recessive for the trait of interest. The ratio of dominant phenotypes (if any) in the progeny
makes clear whether the unkno genotype is heterozygous, homozygous dominant, or homozygous
recessive.< br>孟德尔关于显性和隐性遗传实验的结果称为孟德尔第一定律：
分离定律。
这一定律
认为对于某一特定形状，
有机体继承了每一个亲本的等位基因。
这些等位基因在一起形成了< br>等位基因对。当减数分裂形成配子时，两个等位基因分离（染色体数目减半）
。为验证此理
论，
孟德尔做了测交实验，
即基因型未知的植物与某一隐性纯合体的植物杂交。
根据 后代中
显性基因型的比例可以搞清未知基因型是杂合、纯合显性还是纯合隐性。



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.
孟德尔也开展了双因子 杂合体杂交实
验，
双因子杂合试验，
使得他考虑两个性状如何有关联的遗传。
试验结果产生独自分配定律，
即控制不同性状的等位基因独立遗传。
孟德尔定律的一个明显例外 情况是不完全显性。
杂交
后代的表型是亲本的中间类型。
然而，
不完全显性说 明了两个等位基因对表型都有影响。
等
位基因自身仍然是独立的。

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，孟德尔在布鲁恩自然历史学会出版的科学报上发表了他的观点。不幸的是，他的研究不被当时科学家接受。在
1900
年，他的著作被

Carl
Correns
和
Hugo
de
Vries
重新
发现。

。

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 chromosome 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.
孟德尔的工作被重新发现不久，
Walter Sutton
和
Theodor Boveri
分别提出，
遗传单位可能位
于染色 体上。这一假设被哥伦比亚大学的
Thomas Hunt Morgan
和他的学生用果蝇 的性染色
体实验进行了证实。
摩根的研究也是性连锁特性的首次探索。
它导致了
1916
年
Calvin Bridges
的不分离现象的发现，即在减数分裂中，染色体对不分离。

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
Garrod
爵士是第一个研究基因如何影响表型
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
发现关于特定基因和控制果蝇中复眼颜色的生物合成反应之间的关系。
接着，
在一系列关于< br>面包霉粗糙脉孢霉突变效应的经典实验中，
Beadle
和
Tatum 探究了一基因一酶假设，这一
假设认为每一个基因编码一个特定的酶。
他们的工作为其他研 究者以精确方式阐明酶影响复
杂代途径铺平了道路。

在
1949
年 ，在研究了镰刀形红细胞贫血症中血红蛋白的作用后，
Linus Pauling
帮助将一基因一酶假设精炼成为一基因一多肽假设。


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 experime 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.
核酸最早由
Johann Miescher
在
1871
年分离。 在
20
世纪早期，采用由
Feulgen
建立的红染
方法，
核酸被鉴定为组成染色体的基本成分，
Frederick Griffith
采用
R
和
S
菌株对肺炎双球
菌进行染色 ，表明来自于一个细菌的未知物质能够改变另一细菌的物理性状。在
20
世纪
40年代，
Avery
、
MacLeod
和
McCarty
组成的团队，表明这一未知物质是
DNA
。大约是同一
时代，
P.A.
Levene
发现
DNA
包括四种含氮碱基，每一种碱基与一个核糖分子 和一个磷酸
基相连，
Levene
称这种组合为核苷酸。

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.
在二十世纪
50
年代早期

Martha
和
Alfred
Hershey
关于大肠杆菌的工作清楚地表明遗传信息 的载体是
DNA
，而不是蛋白质，这样就
结束了关于ＤＮＡ是否能够携带复杂的遗传信 息的争论。


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
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.
每一个核苷
酸都含有一个五碳糖，脱氧核糖，分别连 在四种碱基的其中一种之一上，即：腺嘌呤、鸟嘌
呤、
胞嘧啶和胸腺嘧啶。
腺嘌呤和鸟 嘌呤分子是被称为嘌呤的双环结构，
而胞嘧啶核胸腺嘧
啶是被称为嘧啶的单环结构。由一个碱基 和一个糖分子构成的分子称为核苷。
DNA
的每个
分子中磷酸基团连接了链上一个核苷 的五碳糖和相邻核苷的五碳糖。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 ff
规则定义了如下事实，
(1) DNA
中腺 嘌呤数量与胸腺嘧
啶的数量相同，
胞嘧啶和鸟嘌呤的数量相同；
（
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。

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< br>年代末
50
年代初，研究
者利用
Chargaff
的观点、
Levene
关于
DNA
组分的思想和其他两条证据去研 究
DNA
结构。
一个是
Linus Pauling
的观点，认为
DNA
可能是由氢键在确定位置形成的螺旋结构，
另一个
证据是由< br>Franklin
和
Wilkins
拍摄的
DNA X-
衍射照片，
在每一圈之间存在距离的螺旋结构。

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.
在这一信息的基础上，
Watson
和
Crick < br>提出了
DNA
双螺旋模型，
一个象
盘旋曲折的梯子样的分子，外面含有
2
条糖
-
磷酸基链，里面是核苷对形成的横档。成对的
核苷通常以< br>A-T
或
G-C
以氢键相连。
Watson
和
Crick
也提出遗传信息是由
DNA
分子上的
碱基对序列进行编码的。

In their model of DNA structure and function, Watson and Crick hypothesized that DNA replicates
itself by
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
在
DNA
结构与功能的模型中，
Watson
和
Crick
假设，
DNA
通过将连接
A
和T
、
C
和
G
的氢
键解开来自我复制。这一过程将产生两 条互补链，它们方向相反，将作为组建新链的模板。
这是半保留复制的模型，
叫做半保留是因为 每一个新分子具有原来亲本分子的一半，
后来被
Meselson
和
Stahl
的工作所证明。

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 molecu le.
在大肠杆菌中，
DNA
的复制从环形染色体上的泡状结构开始，环形染色
体由复制叉开始。细菌
DNA
复制的研究表明
DNA
链长度只在
5’
至
3
方向（从
5’
端一个核
糖的碳原子，到相邻核糖的
3’
端碳）延长，前导链连续合成，后随链以被称为冈崎片段的
短片段方式合成。游离的核苷排列在父本分子的原初链形成的模板上，
由
DNA
聚合酶催化。

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.
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）
。

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, 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.
生命起源的故事看开始于地球的形成。大爆炸是我们行星形成的开始。大约
50
亿年前，位于太阳系中心的太阳由云状的原始
物质（星际物质）收缩形成。包括地球在的行星在
46
亿年前形成。地球由多层组成： 固态
的地壳，半固态的地幔，很大程度上熔化（液态的）的地核，地核含有一个固态的中心（固
态核）
。地球的基本特征包括行星的大小、温度、组成以及离太阳的距离，使生命出现成为
可能 。当前主要假设认为，在早期地球上非生命物质通过化学演化自发地产生生命。


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
Miller
和
Urey
的开创性的工作，
已成功地制造出包括氨基酸、
简单糖类和核酸碱基等有机单体。
这些单体自发的连接成多聚体，
如类蛋白和核酸，< br>使进入
生命状态成为可能。如今的研究工作表明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.
研究者业已发现，
当一个系统获得能量时，
它们将产生
3
种有机分子聚合体。
俄国科学家
Aleksandr Pparin
从聚合体溶液中得到了富含
多聚体的小滴，被称为团聚体。
Sidney
Fox
用氨基酸和水制造了类蛋白质微球。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