Cell Cycle (Mitosis)

Summary

The video provides a detailed overview of the cell cycle, focusing on mitosis. It explains key stages, such as prophase, metaphase, anaphase, and telophase, with emphasis on chromosome duplication, alignment, and separation. Viewers are guided through how chromosomes and chromatids behave during these phases, and how centrosomes play a crucial role in cell division. The video also touches on cytokinesis, the final step where the cell divides into two daughter cells. The importance of understanding chromosome numbers throughout mitosis is highlighted for a clearer grasp of the process.

Takeaways

• 🧬 The cell cycle consists of two main phases: Interphase and M Phase.
• 🔬 Mitosis occurs during M Phase and is the process where a cell divides to produce two daughter cells.
• 🔄 In Prophase, duplicated chromosomes become visible, and the centrosomes form the mitotic spindle.
• 📏 During Prophase, the cell has 46 chromosomes (23 pairs) with 92 chromatids.
• 🎯 In Prometaphase, microtubules attach to chromosomes at the centromeres, moving them towards the spindle equator.
• 🧲 In Metaphase, chromosomes align at the metaphase plate, and the centrosomes are on opposite sides of the cell.
• 🔗 Anaphase involves the separation of chromatids, with each chromatid pulled to opposite spindle poles.
• ⚖️ In Anaphase, the cell now has 92 chromosomes and 92 chromatids as chromatids are split into separate chromosomes.
• 🌀 Telophase sees chromosomes cluster at opposite poles, nuclear envelopes reform, and organelles reassemble.
• ✂️ Cytokinesis is the final step of the M Phase, resulting in two daughter cells, each with 46 chromosomes and 46 chromatids.

Q & A

What are the two main phases of the cell cycle?

The cell cycle consists of two main phases: interphase and the M phase. M phase includes mitosis, where cell division occurs.

What happens during prophase in mitosis?

In prophase, the chromosomes condense and become visible. The centrosomes start forming the mitotic spindle, and the nuclear envelope begins to break down.

What is the role of the centromere during mitosis?

The centromere is the region that holds duplicated chromosomes together. It plays a key role in chromosome separation by attaching to microtubules from the centrosomes.

How do the chromosomes behave in prometaphase?

In prometaphase, the nuclear envelope fragments, allowing chromosomes to move freely. The chromosomes attach to the mitotic spindle via their kinetochores and begin to move toward the equator of the cell.

What happens during metaphase in mitosis?

During metaphase, chromosomes align along the metaphase plate (equator of the cell). The centrosomes are positioned on opposite poles, and microtubules connect to the chromosomes, preparing them for separation.

What occurs in anaphase, and how do the chromosomes change?

In anaphase, the centromeres split, and the chromatids are pulled apart by the microtubules toward opposite poles of the cell. Each chromatid becomes a separate chromosome, resulting in 92 chromosomes during this phase.

How does the cell prepare for division during telophase?

During telophase, the chromosomes cluster at opposite poles of the cell, the nuclear envelope reassembles around each group of chromosomes, and the cell begins to reorganize its structures.

What is cytokinesis, and how does it differ from mitosis?

Cytokinesis is the final step of the M phase, where the cell divides into two daughter cells. It is not part of mitosis itself, which is the division of the nucleus. Each daughter cell ends up with 46 chromosomes.

How many chromosomes and chromatids are present in a cell during metaphase?

During metaphase, the cell has 46 chromosomes and 92 chromatids, as each chromosome consists of two chromatids.

What is the significance of understanding chromosome and chromatid numbers during mitosis?

Understanding the number of chromosomes and chromatids at each stage of mitosis helps clarify the process of cell division, ensuring accurate replication and distribution of genetic material to daughter cells.

Outlines

00:00

🔬 Overview of the Cell Cycle and Mitosis

In this introduction, Armand Hassan explains the cell cycle, dividing it into two main phases: interphase and M-phase. The focus is on mitosis, a process within M-phase where a cell divides to produce two daughter cells. The first stage of mitosis, prophase, is described as a phase where duplicated chromosomes appear, and the centrosomes begin forming a mitotic spindle. The genetic material at this stage consists of 46 chromosomes or 23 pairs, with 92 chromatids. Prophase sees the condensation of chromosomal material into visible chromosomes, while the cytoskeleton disassembles and the nuclear envelope starts to degrade, allowing the chromosomes to be free. Prophase transitions into metaphase, which involves two stages, beginning with prometaphase.

05:00

🧬 Prometaphase and Metaphase Breakdown

The focus shifts to prometaphase, where the nuclear envelope fragments further, and the mitotic spindle begins to interact with the chromosomes. Microtubules extend from the centrosomes and attach to the centromeres of the chromosomes. These chromosomes move to the equator of the cell, known as the metaphase plate. In the late stage of metaphase, duplicated chromosomes align along this plate, and centrosomes are positioned at opposite poles of the cell. The genetic makeup remains unchanged from prophase, with 46 chromosomes and 92 chromatids, but the arrangement of chromosomes is crucial for the next phase, anaphase.

🧲 Anaphase: Separation of Chromatids

During anaphase, the centromeres holding the duplicated chromosomes split, allowing the chromatids to separate. The microtubules pull one chromatid toward each centrosome at the opposite poles of the cell. As a result, the 46 chromosomes and 92 chromatids present before anaphase now appear as 92 chromosomes (each chromatid now considered a chromosome). The spindle poles also move further apart in preparation for the final stages of mitosis. The explanation clarifies that the total genetic material of the cell remains the same but reorganized into two sets of chromosomes.

🧪 Telophase: Chromosome Clustering and Nuclear Reformation

Telophase, the final stage of mitosis, is characterized by the chromosomes clustering at opposite spindle poles, the reformation of the nuclear envelope, and the disassembly of the mitotic spindle. The genetic material is organized into two sets, each with 46 chromosomes and 46 chromatids per daughter cell. At this stage, the physical process of cell division is nearly complete, but the final step of the M-phase, cytokinesis, must occur for full division.

🔄 Cytokinesis and Conclusion of Mitosis

Cytokinesis, which follows telophase, is not part of mitosis but completes the M-phase. It involves the separation of the cytoplasm, resulting in two daughter cells, each with 46 chromosomes. The daughter cells can either enter the cell arrest phase or proceed back to interphase for future cell cycles. This marks the conclusion of the division process. The video wraps up with a recap of the entire cell cycle, emphasizing the importance of chromosome and chromatid numbers during each phase for understanding mitosis.

Keywords

💡Interphase

Interphase is one of the two main phases of the cell cycle and refers to the period when the cell is not actively dividing but is preparing for mitosis. It is crucial for cell growth, DNA replication, and regular cellular functions. In the video, it is described as the phase preceding the m-phase (mitosis), ensuring the cell has the necessary components for division.

💡Mitosis

Mitosis is the process of cell division where one cell splits into two genetically identical daughter cells. It consists of several stages, including prophase, metaphase, anaphase, and telophase. The video describes mitosis as a part of the m-phase, where chromosomes are duplicated and separated, ensuring each daughter cell receives the correct genetic material.

💡Chromosome

Chromosomes are long DNA molecules that contain part or all of the genetic material of an organism. In the video, chromosomes are discussed as structures visible during mitosis, and their behavior during various stages, such as condensing during prophase and splitting during anaphase, is key to understanding the cell division process.

💡Chromatid

A chromatid is one half of a duplicated chromosome, which becomes visible during cell division. The video explains that each chromosome consists of two chromatids, which are held together by a centromere. During anaphase, these chromatids are pulled apart, resulting in each daughter cell receiving an equal set of chromatids.

💡Centrosome

Centrosomes are organelles that play a key role in organizing microtubules and forming the mitotic spindle during cell division. The video highlights their importance in creating the spindle apparatus that pulls chromosomes apart during mitosis, specifically during prophase and anaphase.

💡Mitotic spindle

The mitotic spindle is a structure composed of microtubules that segregate chromosomes into daughter cells during mitosis. In the video, it is described as forming during prophase and metaphase, connecting to the chromosomes via the kinetochores and helping pull the chromatids apart during anaphase.

💡Centromere

A centromere is the region of a chromosome where the two sister chromatids are joined together. It is crucial for the movement of chromosomes during mitosis. The video emphasizes the centromere's role in holding duplicated chromosomes together until they are split apart during anaphase.

💡Anaphase

Anaphase is one of the stages of mitosis where the sister chromatids are pulled apart to opposite poles of the cell. The video describes how, during anaphase, the centromeres split and the chromatids separate, moving towards the spindle poles, which is critical for ensuring that each daughter cell inherits the correct number of chromosomes.

💡Metaphase

Metaphase is a stage of mitosis where the chromosomes align in the middle of the cell along the metaphase plate. In the video, it is discussed as a phase where chromosomes are fully condensed and aligned before they are pulled apart, marking the transition into anaphase.

💡Cytokinesis

Cytokinesis is the final step of the m-phase, following mitosis, where the cytoplasm of the parent cell divides, forming two daughter cells. Although it is not part of mitosis itself, the video explains cytokinesis as crucial to physically separating the two new cells, each containing 46 chromosomes, after mitosis is complete.

Highlights

The cell cycle consists of two main phases: interphase and M phase, with mitosis occurring within the M phase.

Mitosis is the process where a cell divides to produce two identical daughter cells.

The first phase of mitosis is prophase, where centrosomes begin forming the mitotic spindle.

In prophase, the genetic material condenses into visible chromosomes, and the nuclear envelope starts to degrade.

Prometaphase follows prophase, where the mitotic spindle connects to the centromeres of chromosomes.

In metaphase, duplicated chromosomes align on the metaphase plate at the center of the cell.

During metaphase, the chromosomes are connected to the centrosomes at opposite poles of the cell.

Anaphase begins when the centrosomes pull the duplicated chromosomes apart, separating chromatids to opposite sides.

In anaphase, each chromatid becomes a chromosome, resulting in 92 chromosomes and 92 chromatids in total.

Telophase is the phase where the chromosomes cluster at opposite poles and a new nuclear envelope forms around them.

At the end of telophase, the cell contains 92 chromosomes and 92 chromatids, distributed between the spindle poles.

Cytokinesis, although not part of mitosis, completes the M phase by dividing the cell into two daughter cells.

Each daughter cell will have 46 chromosomes or 23 pairs after cytokinesis, and each chromosome has one chromatid.

Following cytokinesis, cells can either enter a resting phase or proceed through the interphase again before another mitotic cycle.

Mitosis can be defined as the process by which duplicated chromosomes are separated into two nuclei, facilitating cell division.

Transcripts

Armand Hassan biology and Medicine

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huran just recapping the cell cycle

consists of two main phases the

interphase and the

mhase

mitosis uh occurs within the mphase and

mitosis is the process where a cell will

divide to produced two do

cells the first phase of mitosis is

prophase here we have a cell with um the

duplicated

chromosomes um just recapping what we

see in prophase we have the centrosomes

those important structures for cell

division they begin forming a what's

called mitotic

spindle looking at the genetic material

of the cell during profan

it will have

46 chromosomes or 23 pairs of

chromosomes with 92 chromatids because

one chromosome has two chromatids this

structure in the middle here holding the

duplicated chromosome together is known

as a central mirror and it is important

to know

centrom and croome sounds familiar but

don't get mixed

up so during prophase the chromal

material condenses to form a compact

mitotic chromosome so it becomes visible

the chromosomes essentially the

cytoskeleton is then disassembled and

mitotic uh spindle is

assembled so the centrosomes form a

mitotic spindle the nuclear envelope is

also dispersed so the N the the nucleus

membrane essentially uh starts uh starts

degrading to allow these chromosomes to

be free you can say now prophase will

then enter

metaphase the cell in prophase will then

enter

metaphase metaphase itself has an early

stage and a late stage let's look at the

early stage first known as PR

metaphase here we have the the chrom

just in the

cytoplasm we have the centrosomes

remember forming the mitotic

spindle you will see in prometaphase

that the cell will still have the

fragments of the nuclear envelope that

was uh

degrading the centrosomes itself will

form the mitotic spindle by shooting out

these microt tubules that will connect

to the central mirror of the chromosome

the middle part of the duplicated

chromosome so during prometaphase the

chromosomal microtubules attach to

kinetic cores of the

chromosomes chromosomes are then moved

to the spindle equator which is

essentially the spindle equator is the

middle of the cell the equator of the

cell looking at the genetic material of

this cell during prometaphase it will

still have 46 chromosomes and 92

chromatids the the cell in prometaphase

will then enter metaphase the late stage

where the chromosomes the duplicated

chromosome will will align on the

equator the Centra zomes are on opposite

side of each other in the cell and they

form a massive mitotic spindle with the

microtubules in metaphase so the

chromosomes are aligned along the

metaphase plate which is the equator

here this is a metaphase plate

the duplicated chromones that are

aligned on the metaphase plate will then

be

attached by the Chrome aboral

microtubules um at both

poles what this means is that the Centra

the Centro zomes on each of the poles

will have

microtubules um attaching to the same uh

chromosomes essentially

and so if we look at the genetic

material of the of the cell during the

metaphase it will still have 46

chromosomes with 92 chromatids of

course the cell in metaphase will then

enter

anaphase now this might sound a bit

confusing but I hope you can follow this

so in anaphase essentially the

centrosomes with the microtubular

will pull the

duplicated uh chromosomes apart like so

and so um so one chromatid will go

towards one uh s uh centrosome and the

other will go to the other centrone

because it's being pulled

apart and so in anaphase the Centras

which hold the duplicated chromosomes

together will split and the chromatids

will separate

the chromosomes will then move to

opposite spindle poles the

chromatids and then the spindle poles

will move further apart ready for

division so just recapping this is the

centrosome and this is the Centro Mia

which previously held the duplicated

Chrome

zone so let's look at the process of

what happens with the genetic material

during

anaphase so before anaphase we had

remember a duplicated chromosomes two

chromatids per one chromosome so in

total we had 46 chromosomes and 92

chromatids during anaphase the

microtubules with the centrosomes will

split this apart essentially forming two

chromosomes each with one

chromatid so therefore in total we would

see 92 chromosomes and 92 chromatids in

this

cell I hope this makes

sense now the cell in anaphase will then

enter the last phase of mitosis which is

cello

phase cello phase is essentially when we

see the centrosome with the microt

tubules pulling the chromosomes closer

to each of their poles and then we also

see a membrane forming around

it and so in chillo Phase um what we see

is the chromosomes are clustering at

opposite spindle

poles like so the chromosomes become

dispersed the nuclear envelope will

assemble and the organel will

reform and so this is our nuclear

envelope which is

reassembling

essentially so now if we were look to

look at the the genetic material of the

cell during

Chase it would have this would represent

one

chromosome which has one

chromatid and therefore the cell would

have in total 92 chromosomes and 92

chromatids the cell will then enter

um the last phase of mphase not mitosis

but the last phase of M phase known as

cyto canis now cyto canis is not part of

mitosis but it is part of mphase and it

is essentially the separation of um the

cell into two daughter cells and

therefore each of these um daughter

cells will have

46 chromosomes each or 23 pairs of

chromosomes each and of course one

chromosome will have one chromatid so it

will have 46

chromatids and this is because remember

the cell in cello phase had 92

chromosomes so if this cell with 92

chromosomes divide it will have 46 on

one daughter cell and another 46 in the

other

following cyto canis these cells can

enter the cell arrest phase or it can

enter the whole interphase and then

enter mitosis again after a while or

after some

time so now mitosis can be defined as

the process um by which duplicated

chromosomes separate into two

nuclei and this is essentially

the uh division

process hope you enjoyed this video on

the cell cycle oh we looked at the

interphase and we looked at mitosis in

quite detail it's important to know the

number of chromosomes and chromatids in

each of these steps to understand what

is actually

happening anyway I hope you enjoy this

video thank you