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By the end of this section, you will be able to:
  • Describe the three stages of interphase
  • Discuss the behavior of chromosomes during mitosis and how the cytoplasmic content divides during cytokinesis
  • Define the quiescent G 0 phase
  • Explain how the three internal control checkpoints occur at the end of G 1 , at the G 2 –M transition, and during metaphase

The cell cycle    is an ordered series of events involving cell growth and cell division that produces two new daughter cells. Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages of growth, DNA replication, and division that produce two genetically identical cells. The cell cycle has two major phases: interphase and the mitotic phase ( [link] ). During interphase    , the cell grows and DNA is replicated. During the mitotic phase , the replicated DNA and cytoplasmic contents are separated and the cell divides. Watch this video about the cell cycle: (External Link)

This illustration shows the cell cycle, which consists of interphase and the mitotic phase. Interphase is subdivided into G1, S, and G2 phases. Cell growth occurs during G1 and G2, and DNA synthesis occurs during S. The mitotic phase consists of mitosis, in which the nuclear chromatin is divided, and cytokinesis, in which the cytoplasm is divided resulting in two daughter cells.
A cell moves through a series of phases in an orderly manner. During interphase, G 1 involves cell growth and protein synthesis, the S phase involves DNA replication and the replication of the centrosome, and G 2 involves further growth and protein synthesis. The mitotic phase follows interphase. Mitosis is nuclear division during which duplicated chromosomes are segregated and distributed into daughter nuclei. Usually the cell will divide after mitosis in a process called cytokinesis in which the cytoplasm is divided and two daughter cells are formed.

Interphase

During interphase, the cell undergoes normal processes while also preparing for cell division. For a cell to move from interphase to the mitotic phase, many internal and external conditions must be met. The three stages of interphase are called G 1 , S, and G 2 .

G 1 Phase

The first stage of interphase is called the G 1 phase    , or first gap, because little change is visible. However, during the G 1 stage, the cell is quite active at the biochemical level. The cell is accumulating the building blocks of chromosomal DNA and the associated proteins, as well as accumulating enough energy reserves to complete the task of replicating each chromosome in the nucleus.

S phase

Throughout interphase, nuclear DNA remains in a semi-condensed chromatin configuration. In the S phase    (synthesis phase), DNA replication results in the formation of two identical copies of each chromosome—sister chromatids—that are firmly attached at the centromere region. At this stage, each chromosome is made of two sister chromatids and is a duplicated chromosome. The centrosome is duplicated during the S phase. The two centrosomes will give rise to the mitotic spindle , the apparatus that orchestrates the movement of chromosomes during mitosis. The centrosome consists of a pair of rod-like centrioles at right angles to each other. Centrioles help organize cell division. Centrioles are not present in the centrosomes of many eukaryotic species, such as plants and most fungi.

G 2 Phase

In the G 2 phase    , or second gap, the cell replenishes its energy stores and synthesizes the proteins necessary for chromosome manipulation. Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic spindle. There may be additional cell growth during G 2 . The final preparations for the mitotic phase must be completed before the cell is able to enter the first stage of mitosis.

Questions & Answers

Demand is set to be enlastic when its what
bohvy Reply
more than boll had him had bhaag......
SHADAB
Cant you speak in English
john
a little
Tith
I do speak English.. the question is Demand is set to be elasticity went the dash *2
bohvy
if I want some document from,that 9k?
Tith
why is scarcity a fundamental problem in economic
Abubakar Reply
what is demand curve
Takyi Reply
xplain
Ubong
thanks for your help with the same....
SHADAB
What is elasticity of demand
Karim
what is opportunity cost
Samuel Reply
Opportunity cost which also mean real cost it is a term used for foregone alternatives
john
what is demand
ikea Reply
Demand may simply be define as the total quantity of good or service a consumer are willing to buy at a specific price within a period of time.
john
your language is tough
techy Reply
How economics is related to other subjects?
Mikateko Reply
It is social science related subjects
john
How ? explain
Mikateko
and something else help me about business cycle
Mikateko
s classified as a social science. This view makes eco­nomics an academic relative of political science, sociology, psychology and anthropology. All of these disciplines study the behaviour of human beings individually and in groups.
john
The business cycle describes the rise and fall in production output of goods and services in an economy. Business cycles are generally measured using the rise and fall in the real gross domestic product (GDP) or the GDP.
john
hello everyone
Selena
hii
Yes
hello selena
Yes
How are you doing every one
john
hello Selena
Yes
hi
NONSO
yes
NONSO
What Is Economic Growth?
Saviour Reply
is the increase of quantity of goods ans services
Hashi
what is economic
Yomina Reply
Economic may be define as the science which studies human behaviour in relationship with end and scarce which have alternative use. This definition was drafted by Lionel robbin
john
good
Tith
it is science of wealth.
SHADAB
if I want some documents from you ,Are you ok?
Tith
it is not only wealth as well as welfare also.as well as scarce means of ends,for human satisfaction for alternative uses.
Avijit
economics applications
techy
who should study economics
Mary Reply
hi
Adu
How are you doing
john
finr
Tith
sorry, fine
Tith
and you?
Tith
Good
Adu
where do you live?
Tith
Accra n u
Adu
what's the difference between elasticity and demand
Rich Reply
if country had a potential full employment income of Rs 1000 and following consumption and investment function C=0.75 y=50,I=150.find the level of government expenditure necessary to maintain full employment
Vijay Reply
what is China's economy
Ved
the meaning of elasticity
Yawe Reply
when equilibrium is égal to 1
Moussa
The tendency to change consumption habits with change in price
Iben
The type of elasticity if demand
Okonkwo Reply
aren't leaving too about bathrooms
SHADAB
I don't understand
Amina
like.
Ubong
Price elasticity of demand cross elasticity of demand income elasticity of demand
Lawrence
what is money
Lawal Reply
what is supply
Lawal
the total number of goods present at a particular area at a particular time
Offset
what does post-translational control refer to?
Teresa Reply
Bioremediation includes
Rachel Reply

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Source:  OpenStax, Ucd bis2a intro to biology v1.2. OpenStax CNX. Sep 22, 2015 Download for free at https://legacy.cnx.org/content/col11890/1.1
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