Mitosis Cell Division Animation | Phases of mitosis | Cell Cycle

Summary

This video script delves into the fascinating process of cell division, which allows a parent cell to split into two or more daughter cells. It covers the cell cycle's phases: G1, S, G2, and M, detailing the preparation and execution of division. The script also touches on checkpoints ensuring proper cell division and the significance of the mitotic spindle. It highlights the role of growth factors in re-entering the cell cycle and the variable duration cells spend in the G0 phase, depending on cell type.

Takeaways

• 🌿 Cell division is a biological process where a parent cell divides into two or more daughter cells.
• 🧬 A typical human cell contains 46 chromosomes, including 22 pairs of autosomes and two sex chromosomes.
• 🔄 The cell cycle is a series of stages that prepare a cell for division, with a typical duration of 24 hours for rapidly dividing cells.
• 🔢 The cell cycle is divided into four phases: G1, S, G2, and M, with G1 being the most variable in duration.
• 📈 The G1 phase is critical for the synthesis of RNA, proteins, and cell organelles necessary for cell division.
• 🔬 The S phase is when DNA replication occurs, resulting in two sister chromatids for each chromosome.
• 🛠️ The G2 phase involves further protein synthesis and preparation for mitosis, including organelle and cytoskeleton reorganization.
• 🧐 The M phase, or mitosis, includes stages like prophase, metaphase, anaphase, and telophase, where chromosomes are separated and the cell divides.
• 🔍 The G1 checkpoint ensures cells only enter the S phase when growth signals are present, preventing unregulated cell division.
• 🔄 The G2 checkpoint verifies DNA replication completeness and integrity before cells enter mitosis.

Q & A

What is cell division?

Cell division is a biological process by which a parent cell divides into two or more daughter cells, duplicating each chromosome into two sister chromatids and distributing them equally to ensure each new cell has the same genetic material.

How many chromosomes does a typical human cell contain?

A typical human cell contains 46 chromosomes, which include two copies of the 22 homologous chromosomes and two copies of the sex chromosomes.

What are the four phases of the cell cycle?

The four phases of the cell cycle are G1 (Gap 1) phase, S (Synthesis) phase, G2 (Gap 2) phase, and M (Mitosis) phase.

What is the duration of the cell cycle for a rapidly dividing human cell?

The total cell cycle time for a typical rapidly dividing human cell is 24 hours, with the shortest phase being 12 hours.

What happens during the G1 phase of the cell cycle?

During the G1 phase, the cell synthesizes RNA, proteins, and cell organelles, and grows. It also prepares for mitosis by synthesizing proteins required for the mitotic spindle. A G1 checkpoint ensures that the cell does not enter the S phase without proper growth signals.

What is the main event of the S phase?

The S phase is characterized by the replication of DNA, resulting in each chromosome having two copies, or sister chromatids, which are held together by cohesion proteins at the centromere.

What is the role of the G2 checkpoint in the cell cycle?

The G2 checkpoint occurs at the end of the G2 phase and checks for DNA damage and the completeness of DNA replication. It ensures that the cell is ready to enter mitosis by facilitating the initiation of mitosis through phosphorylation of various proteins.

What are the four stages of mitosis?

The four stages of mitosis are prophase, metaphase, anaphase, and telophase. These stages involve the condensation of DNA, alignment and separation of sister chromatids, and the physical division of the cell into two daughter cells.

What is the significance of the spindle checkpoint in mitosis?

The spindle checkpoint, also known as the M checkpoint, occurs between metaphase and anaphase in mitosis. It ensures the correct alignment of chromosomes and sister chromatids at the equatorial plane before they are separated, preventing errors in chromosome distribution.

What is cytokinesis and how does it relate to cell division?

Cytokinesis is the final step in cellular division where the cell physically divides into two daughter cells. It is characterized by the formation of a cleavage furrow in the cell membrane and the separation of the cell bodies, marking the end of one cell cycle and the beginning of two new ones.

What is the G0 phase and how does it differ from other phases of the cell cycle?

The G0 phase is a resting phase where the cell exits the cell cycle and becomes quiescent until it receives external stimuli such as growth factors. Unlike other phases, G0 is not part of the active cell cycle and can last indefinitely, depending on the cell type.

Outlines

00:00

🌱 Cell Division and Cycle Overview

This paragraph introduces cell division, a critical biological process where a parent cell divides into two or more daughter cells. It discusses the typical human cell's 46 chromosomes, which include 22 pairs of homologous chromosomes and two sex chromosomes. During cell division, the cell's contents, including organelles and the cytoskeleton, are duplicated, and each chromosome is copied into two sister chromatids. The cell cycle, which includes the phases G1, S, G2, and M, is outlined as the sequence of events leading to the production of two identical daughter cells. The total cell cycle time for a rapidly dividing human cell is 24 hours, with the shortest phase being 12 hours. The paragraph also delves into the interphase, which includes G1, S, and G2 phases, preparing the cell for division. The G1 phase is highlighted for its variable duration and critical role in RNA, protein, and organelle synthesis, as well as the G1 checkpoint that ensures cells only divide with proper growth signals.

05:03

🔬 Detailed Cell Cycle Phases and Checkpoints

The second paragraph delves deeper into the specific phases of the cell cycle, focusing on the S, G2, and M phases. The S phase, lasting approximately 8 hours, is when the cell replicates its DNA, creating two copies of each chromosome known as sister chromatids. The G2 phase, approximately 2 to 5 hours long, is characterized by cell growth and preparation for division, including the synthesis of proteins required for mitosis. The M phase, or mitosis, involves the condensation of DNA into visible chromatids, their separation, and movement to opposite cell poles, culminating in cell division into two daughter cells. The paragraph also explains the checkpoints within the cell cycle, such as the G2 checkpoint that checks for DNA damage and replication completeness, and the spindle checkpoint that ensures correct chromosome alignment before separation. The paragraph concludes with a discussion of cytokinesis, the physical division of the cell, and the G0 phase, where cells exit the cell cycle and become quiescent until stimulated to re-enter the cycle.

Keywords

💡Cell Division

Cell division is a biological process where a parent cell divides into two or more daughter cells. This process is crucial for growth, repair, and maintenance of living organisms. In the video, cell division is the central theme, with a focus on how it ensures that each new cell receives a complete set of genetic material. The script describes the process in detail, including the doubling of cellular contents and the duplication of chromosomes into sister chromatids.

💡Chromosomes

Chromosomes are thread-like structures made of DNA and protein found in the nucleus of cells, carrying genetic information. The video script mentions that a typical human cell contains 46 chromosomes, which are duplicated during cell division to ensure that each daughter cell receives the same genetic information as the parent cell. Chromosomes play a critical role in maintaining genetic integrity across generations.

💡Cell Cycle

The cell cycle is the series of events that take place in a cell leading to its division and duplication. The video script outlines the cell cycle as having four main phases: G1, S, G2, and M. Understanding the cell cycle is essential for grasping how cells grow and divide, and the video emphasizes the orderly sequence of events that prepare a cell for division.

💡Interphase

Interphase is the phase of the cell cycle during which the cell is not dividing but is preparing for division. It includes the G1, S, and G2 phases. The video script explains that interphase involves the synthesis of RNA, proteins, and cell organelles, which are necessary for the cell to divide. This phase is critical for ensuring that the cell has all the necessary components to successfully undergo division.

💡Mitosis

Mitosis is the phase of the cell cycle where the cell's nucleus divides, resulting in two daughter cells each with the same number of chromosomes as the parent cell. The video script describes mitosis as involving several stages, including prophase, metaphase, anaphase, and telophase, where sister chromatids are separated and moved to opposite poles of the cell. Mitosis is a key process in the cell cycle, ensuring genetic material is accurately distributed to new cells.

💡Sister Chromatids

Sister chromatids are identical copies of a chromosome that are joined together at the centromere. The video script explains that during cell division, each chromosome is duplicated into two sister chromatids, which are then separated and distributed to the daughter cells. The concept of sister chromatids is central to understanding how genetic material is preserved and passed on during cell division.

💡Centromere

The centromere is the region of a chromosome where sister chromatids are joined together. As mentioned in the video script, it plays a crucial role in cell division by ensuring that sister chromatids stay together until it is time for them to be separated and distributed to the daughter cells. The centromere is a critical structure for maintaining the correct number of chromosomes in each new cell.

💡G1 Checkpoint

The G1 checkpoint, also known as the restriction checkpoint, is a control point in the cell cycle that determines whether the cell will proceed to the S phase. The video script highlights that this checkpoint ensures the cell has received appropriate growth signals before committing to DNA replication. It is a regulatory mechanism to prevent uncontrolled cell division, which can lead to diseases such as cancer.

💡Cytokinesis

Cytokinesis is the final stage of cell division where the cytoplasm of the parent cell divides, resulting in two separate daughter cells. The video script describes cytokinesis as involving the formation of a cleavage furrow in the cell membrane, marking the physical separation of the two new cells. This process is essential for completing cell division and ensuring that each daughter cell is viable.

💡G0 Phase

The G0 phase is a resting phase where cells exit the cell cycle and become quiescent. The video script explains that cells in the G0 phase do not divide until they receive external stimuli, such as growth factors. This phase is important for understanding how cells can remain in a non-dividing state for extended periods, which is crucial for the long-term survival of certain cell types like neurons.

Highlights

Cell division is a process where a parent cell divides into two or more daughter cells.

A typical human cell contains 46 chromosomes, including 22 pairs of homologous chromosomes and two sex chromosomes.

During cell division, the cell's contents, including organelles and the cytoskeleton, are duplicated.

The cell cycle is the sequence of events leading to cell division, typically taking 24 hours for a rapidly dividing human cell.

The cell cycle consists of four phases: G1, S, G2, and M, with G1 being the most variable in duration.

The G1 phase is critical for the synthesis of RNA, proteins, and cell organelles required for mitosis.

The G1 checkpoint ensures cells do not enter the S phase without proper growth signals.

The S phase is where the cell replicates its DNA, creating two copies of each chromosome.

Sister chromatids, formed during S phase, are held together by cohesion proteins at the centromere.

The G2 phase involves further protein synthesis and preparation for cell division.

The G2 checkpoint checks for DNA damage and ensures the completeness of DNA replication.

M phase is the final step in cellular division, where DNA condenses and sister chromatids are separated.

Prophase is characterized by the condensation of DNA into 46 pairs of sister chromatids.

Metaphase involves the alignment of sister chromatid pairs at the cell's center for separation.

The spindle checkpoint in metaphase ensures correct chromosome alignment before separation.

Anaphase is the stage where sister chromatids separate and move to opposite cell poles.

Telophase is marked by chromosome decondensation, nuclear membrane formation, and cell body division.

Cytokinesis is the physical division of the cell into two daughter cells, marked by cell membrane cleavage.

The G0 phase is a resting state where cells exit the cell cycle until stimulated by growth factors.

Growth factors initiate a signaling cascade necessary for cell division in response to external stimuli.

Transcripts

[Music]

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