Mitosis Cell Division Animation | Phases of mitosis | Cell Cycle

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cell division introduction cell division

is a process by which a parent cell

divides into two or more daughter cells

a typical human cell contains 46

chromosomes two copies of the 22

homologous chromosomes plus two copies

of the sex chromosome when the cell

divides it roughly doubles all of its

contents including organel and the

cytoskeleton and duplicates each

chromosome into two sister chromatids

the cell then splits the large double

cell into two identical daughter cells

each with the same 46 chromosomes as the

mother cell cell cycle it is the ordered

sequence of events that occur in a Cell

in the preparation of cell division to

produce two daughter cells the total

cell cycle time for a typical rapidly

dividing human cell is 24 hours and the

most minimum time is 12 hours the cell

cycle can be divided into four phases G1

Gap 1 phase s or DNA synthesis phase G2

Gap 2 phase M mitosis phase the cell

involves two phases interphase and

mitosis interphase further involves the

G1 phase or Gap One S phase synthesis

and G2 phase Gap 2 which prepare the

cell for division G not phase is not a

part of interphase the time taken for S

G2 and M are similar for most cell types

G1 phase lasts several hours to months S

phase lasts for 6 to 8 hours G2 phase

lasts approximately 2 to 5 hours and M

phase for 1 to 2 hours in contrast the

duration of G1 phase shows a vast

variation in a rapidly dividing phase G1

phase can be less than 2 hours in a

resting cell G1 phase can be Beyond 100

hours or more in ovaries primary us

sites remain in ditin stage of meosis

from fifth month of intrauterine life

until the period before ovulation begins

let's focus on events which takes place

during each phase G1 phase this phase

lasts for several hours to months and

occurs after

mitosis this phase is critical For the

synthesis of RNA proteins and cell

organel the synthesis of proteins that

are required for mitosis such as the

mitotic spindle is particularly

important important during this phase

there is one chromatid present per

chromosome the cell grows during this

phase nucleotide excision repair takes

place at the end of this phase there is

a G1 checkpoint before entering S phase

G1 checkpoint or restriction checkpoint

is a cell division checkpoint that

restricts entry into the synthesis or S

phase without growth signals that lift

this checkpoint cells will not divide

after this checkpoint cells become

committed to division loss of this

checkpoint for example from loss of p-53

function leads to unregulated cell

division S phase this phase lasts for

approximately 8 hours during the S phase

the cell replicates its DNA so that by

the end each chromosome has two copies

the copies are attached to each other by

cohesion proteins in a structure called

a centromere and together they're

referred to as sister chromatids each

pair of sister chromatids is considered

to be one chromosome because they are

just copies of the same genetic material

and still attached to one another this

phase of the cell cycle is where

histones the proteins that bind and

organized DNA are duplicated at this

point the cell has double the amount of

genetic material most mismatch repair

takes place during the S phase once the

S phase is initiated the cell must be

completed G2 phase this phase lasts for

approximately 2 to 5 hours during G2 the

cell continues to grow and prepares for

division by reorganizing its organel and

cytoskeleton this phase is characterized

by further synthesis of proteins

required for mitosis at the end of G2

phase and before entering the the

mitosis there is a checkpoint known as

G2 checkpoint G2 checkpoint is a cell

division checkpoint that occurs during

the G2 phase which checks for DNA damage

and completeness of DNA replication it

facilitates the initiation of mitosis

through phosphorilation of various

proteins for example histones regulat

synchronized cell division mediated by

mitosis promoting factor that cycl B

cdk1 complex M phase in the M phase the

DNA condenses to form visible pairs of

sister chromatids attached at the centrr

they're subsequently separated and moved

to opposite poles of the cell after the

M phase the cell splits into two

daughter cells in a process called cyto

Kinesis karyotypes are obtained from

cells in the M phase mitosis is the

final step in cellular division prior to

the two daughter cells separating from

one another and it has four stages stage

one prophase profase is a stage during

which the DNA condenses into 46 pairs of

sister chromatids linked together at the

center by a centrr centrr keep the

sister chromatids together until it is

time to separate and ensure that each

daughter cell gets the right sister

chromatids without any duplicates or

loss

centrosome separation the centrosome is

the point of origin of the mitotic

spindle it consists of two centrioles

and a surrounding Matrix from which the

microtubules emerge prophase is a stage

of formation of the mitotic spindle

stage two metaphase metaphase is a stage

during which all the sister chromatid

pairs align at the center of the cell

and prepare for separation this is a

crucial step in which checks are made to

make sure that all the chromosomes are

attached to the mitotic Centrum mirors

in such a way that when they are pulled

apart the sister chromatids are evenly

split between the two new cells clinical

link Vin Christen a chemotherapy drug

prevents the formation of microtubules

that attach to the centrom in mitosis M

checkpoint spindle checkpoint it is a

third checkpoint between metaphase and

anaphase in mitosis this checkpoint

ensures correct alignment of the

chromosomes and sister chromatids at the

equatorial plane before the separation

of sister chromatids stage three

anaphase in anaphase the sister

chromatid start separating and moving to

the opposite poles of the cell stage

four tase in tase the cell starts

physically dividing into two it is

characterized by DEC condensation of the

chromosomes disintegration of the

mitotic spindle formation of a new

nuclear membrane cell bodies division at

the equatorial plane ribosomal RNA

synthesis clinical link proper

functioning of the mitotic spindle is a

prerequisite for chromosome

Transportation inhibition with spindle

poisons leads to arrest of mitosis and

cation of cell division spindle poisons

includ cesin as well as vinka alkaloids

and taxanes which inhibits microtubular

polymerization cytokinesis it is usually

marked by formation of a Clift in the

cell membrane as the mother cell starts

dividing into two daughter cells coming

to the G not phase it is also known as

the resting phase during the G not phase

the cell exits the cell cycle and

becomes quiescent until it receives

external stimuli in the form of growth

factors to start replicating again at

which time it will enter back into the

cell cycle at the G1 stage growth

factors are of different forms including

hormones and proximity signals from

nearby cells these ultimately initiate a

signaling Cascade inside the cell that

activates the proteins necessary for

initiation of cell division the amount

of time a cell spends in G not phase is

dependent on the cell type mature

neurons spend most if not all of their

lifespan in G not phase while cells that

produce the intestinal lining May rarely

or never enter G not

phase