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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 karyokinesis
  • Explain how the cytoplasmic content is divided during cytokinesis
  • Define the quiescent G 0 phase

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 produces two identical (clone) 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.

Like a clock, the cell cycles from interphase to the mitotic phase and back to interphase. Most of the cell cycle is spent in interphase, which is subdivided into G_{1}, S, and G_{2} phases. Cell growth occurs during G_{1}, DNA synthesis occurs during S, and more growth occurs during G_{2}. 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.
The cell cycle consists of interphase and the mitotic phase. During interphase, the cell grows and the nuclear DNA is duplicated. Interphase is followed by the mitotic phase. During the mitotic phase, the duplicated chromosomes are segregated and distributed into daughter nuclei. The cytoplasm is usually divided as well, resulting in two daughter cells.

Interphase

During interphase, the cell undergoes normal growth processes while also preparing for cell division. In order for a cell to move from interphase into 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 (first gap)

The first stage of interphase is called the G 1 phase    (first gap) because, from a microscopic aspect, 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 sufficient energy reserves to complete the task of replicating each chromosome in the nucleus.

S phase (synthesis of dna)

Throughout interphase, nuclear DNA remains in a semi-condensed chromatin configuration. In the S phase    , DNA replication can proceed through the mechanisms that result in the formation of identical pairs of DNA molecules—sister chromatids—that are firmly attached to the centromeric region. 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. At the center of each animal cell, the centrosomes of animal cells are associated with a pair of rod-like objects, the centrioles , which are at right angles to each other. Centrioles help organize cell division. Centrioles are not present in the centrosomes of other eukaryotic species, such as plants and most fungi.

G 2 Phase (second gap)

In the G 2 phase    , the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation. Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic phase. 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

what is hominids
Dauba Reply
what is genetics
Musa Reply
what is meiosis?
Musa
list three vertebrate animal and three invertebrate animal
Katie Reply
lizard, goat, frog ,earthworm, housefly, tapeworm
idoko
what is meant by radial symmetry?
Boadi
what is meaning of polysaccharide
mark Reply
water as a function in cell for inorganic substances
chisom Reply
hi john....wat about for mineral salts, its function in a cell and structure
chisom
hi chisom which topic is this
Ezeh
what is sepsis
Dauba
this biology is for which grade?
Janet Reply
A1
Boadi
state any one specialized animal cell and it's function
Pascal Reply
sperm cell: Fertilization
Tshering
Can DNA and RNA be praticalized
Oyewale Reply
you can make models of them and show how they replicate
Oswald
what is dentition
Tisa Reply
Study of teeths and their functions
Stanisla
what are the function
Tisa
it's not teeths. teeth is plural as well as singular noun. the function of the teeth is to cut and grind food for easier swallowing and for increasing the surface area if the fish as the substrate in which digestive enzymes work
Oswald
dentition is not the study of teeth but the arrangement of teeth in the mouth of species or individuals
Oswald
what are the two types of teeth
Tisa
upper lower jaw and upper jaw teeth
Dauba
Function of probosis
Adeola Reply
why do we study biology?
SYDNEY Reply
where biology began
Alhaji
What are chromesome
Talkmore Reply
condensed DNA wrapped with histone
Elias
chromosomes are gins that we take from our parents.when mom get pregnant the baby inside is made up of 23 chromosomes from his dad and 23 chromosomes from his mom.so a baby is made up of totally 46 chromosomes
ezera
chromosome are rod or thread shape body located in the nucleus of a cell.
Alhaji
what are chromosomes
Persiviour
what is chromosome?
Royd Reply
How can a person who has been in the vascular disease repairs his or her DNA
Rabson Reply
i need its explanation sir..pls provid na...🙁
Shaf Reply
Of wat
John
explanation for wat
Christian
Of war na so dat I can provide
John
Is d process which food is converted into substance dat can be utilize by d body
John

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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