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Year 12 - Biology > C8 - Mitosis > Flashcards

C8 - Mitosis Flashcards

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1
Q

What is mitosis?

A

Division of a cell into two daughter cells which are genetically identical to each other and the parent cell.

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2
Q

What are the 3 main stages of the cell cycle during mitosis?

A

Interphase (divided into 3 parts)

Mitosis (divided into 4 parts)

Cytokinesis

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3
Q

What are the 3 parts of interphase?

A

G1 (first growth)

S (synthesis phase)

G2 (second growth)

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4
Q

What occurs during the 3 stages of interphase?

A

G1 - The cell grows in size. Proteins are synthesised, enabling new organelles to be produced.

S - DNA is replicated

G2 - Cell growth and protein synthesis continue. Organelles grow and divide. The cell builds up its energy stores.

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5
Q

What are the four parts of mitosis/nuclear division?

A

Prophase

Metaphase

Anaphase

Telophase

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6
Q

What occurs during cell division / how does the cell divide in mitosis?

A

By cytokinesis at the end of the cell cycle

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7
Q

What are cyclins?

A

Proteins which regulate the cell cycle by activating enzymes known as cyclin-dependent kinases (CDKs) which control each step of the cycle.

This means the cell cycle can be stopped when errors are detected to enable the cell to repair the DNA. (If unsuccessful, it can cause cancer).

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8
Q

What proteins regulate the cell cycle?

A

Cyclins

They activate enzymes known as cyclin-dependent kinases (CDKs) which control each step of the cycle.

This means the cell cycle can be stopped when errors are detected to enable the cell to repair the DNA.

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9
Q

Why is mitosis / replication of genetically identical cells important?

A

For growth in multicellular organisms

Repair in tissues

Replacement

Asexual reproduction

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10
Q

What is DNA like during interphase?

A

It is uncoiled and not visible as chromosomes

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11
Q

What occurs during prophase?

A

DNA condenses (forming coils using proteins called histones) and chromosomes become visible.

Each chromosome consists of two chromatids which are identical due to DNA replication and are joined at their centromeres.

Centrioles move to opposite poles of the cell and begin to produce microtubules called spindle fibres.

The nucleolus and nuclear envelope break down so chromosomes are free to move

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12
Q

What occurs during metaphase?

A

The spindle fibres produced by the centrioles grow further and attach to the centromeres on each chromosome.

The chromosomes are then pulled in line to the equator of the cell.

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13
Q

What occurs during anaphase?

A

The microtubules that make up the spindle fibres are pulled back towards the centrioles causing the centromeres to divide and the two chromatids on each chromosome are pulled to opposite poles of the cell.

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14
Q

What occurs during telophase?

A

The spindle fibres break down and disappear.
Two new nuclear envelopes begin to form around the two identical sets of chromatids which can now be referred to as ‘daughter chromosomes’.

The DNA starts to uncoil again and the chromosomes disappear.

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15
Q

What occurs during mitosis?

A

Prophase - DNA condenses (forming coils using proteins called histones) and chromosomes become visible.

Each chromosome consists of two chromatids which are identical due to DNA replication and are joined at their centromeres.
Centrioles move to opposite poles of the cell and begin to produce microtubules called spindle fibres.
The nucleolus and nuclear envelope break down so chromosomes are free to move

Metaphase - The spindle fibres produced by the centrioles grow further and attach to the centromeres on each chromosome.
The chromosomes are then pulled in line to the equator of the cell.

Anaphase - The microtubules that make up the spindle fibres are pulled back towards the centrioles causing the centromeres to divide and the two chromatids on each chromosome are pulled to opposite poles of the cell.

Telophase - The spindle fibres break down and disappear.
Two new nuclear envelopes begin to form around the two identical sets of chromatids which can now be referred to as ‘daughter chromosomes’.
The DNA starts to uncoil again and the chromosomes disappear.

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16
Q

What takes place during cytokinesis?

A

(After telophase)

The cytoplasm is divided between the two daughter cells to finish the cycle.

17
Q

What is mitotic index and how is it calculated?

A

How fast cells replicate

(Number of cells in mitosis / total # of cells) * 100

18
Q

How does mitosis differ between animal and plant cells?

A

It occurs in all animal tissues (except sex cells) whereas it only occurs in meristematic tissues in plants

Cellulose cell wall of plant cells prevents shape change during division

Spindle fibres remain during cytokinesis for plant cells.

Microfilaments aren’t as significant in plants

19
Q

What is apoptosis?

A

It is the ‘normal’, ‘programmed’ cell death during normal or biological processes.

It is the process where cells are removed (cell death)

20
Q

What is necrosis?

A

‘Accidental’ or ordinary cell death due to a serious chemical or physical insult (infection or trauma)

21
Q

Why is apoptosis necessary?

A

Cell death is required to prevent there from being too many cells.
This helps for digit formation during embryonic development.
It’s also necessary for nerve development and the destruction of potentially harmful immune cells

22
Q

How does necrosis occur?

A

The volume of the cell increases and the cell is enlarged, causing the cytoplasm to swell.
This results in the release of hydrolytic enzymes

23
Q

What are the stages of apoptosis?

A

1) The cell shrinks and the nucleus condenses (pyknosis)
2) Enzymes break down the cytoskeleton
3) The cell surface membrane alters and forms bulges known as blebs
4) The nucleus breaks down (karyorrhexis)
5) The cell is broken into fragments which are held in vesicles called apoptic bodies
6) Phosphatidylserine, a phospholipid normally found on the inside of cell membranes, is present on the outside of vesicles
7) Phosphatidylserine binds to receptors on immune cells called macrophages.
8) Macrophages engulf the fragments

24
Q

What’s the purpose of phosphatidylserine during apoptosis?

A

Phosphatidylserine, a phospholipid present outside the vesicles, binds to receptors on immune cells called macrophages.

These macrophages engulf the fragments of the cell.

25
Q

What is karyorrhexis?

A

When the nucleus breaks down

26
Q

What is pyknosis?

A

When the cell shrinks and the nucleus condenses during apoptosis

27
Q

What’s differentiation?

A

When a stem cell changes and becomes specialised

28
Q

What are totipotent stem cells?

A

Stem cells found in very early embryos which can differentiate into ANY type of cell and can divide to form a whole organism.
(E.g. Chorion or amnion)

29
Q

What are pluripotent stem cells?

A

Stem cells which can differentiate into ANY type of cell that makes up the body but cannot divide to form a whole organism.

30
Q

What are multipotent stem cells?

A

Stem cells which can differentiate into a limited range of cell types

E.g. Stem cells in adult bone marrow can form blood cells but not nerve cells

31
Q

What is a blastocyst?

A

A stem cell taken from a dividing embryo at a very early stage

32
Q

Where are the inner cell mass and trophectoderm found?

A

Inner cell mass - many cells within the blastocyst

Trophectoderm - outer layer of cells of the blastocyst

33
Q

How can multipotent adult stem cells be used?

A

For transplants e.g. Bone marrow transplants to treat leukaemia.

34
Q

How can pluripotent embryonic stem cells be used?

A

Cell replacement therapies

Testing potential drugs in vitro

Studying the development of diseases in vitro

Year 12 - Biology (15 decks)

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