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cell cycle Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

List the stages of the cell cycle in order

A 
G1
S
G2
Mitosis
Cytokinesis 
G0
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2
Q

Describe what happens during interphase.

A
  • DNA is replicated
  • protein synthesis occurs in the cytoplasm
  • mitochondria grow and divide, increasing in number
  • in plants, chloroplasts also grow and divide
  • normal metabolic processes occur.
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3
Q

Describe what happens in G1 phase of interphase.

A

The first growth phase. Proteins from which organelles are synthesised are made and organelles replicate. The cell grows in size

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4
Q

Describe what happens in S phase of interphase.

A

DNA is replicated

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5
Q

Describe what happens in G2 phase of interphase

A

The second growth phase. The cell continues to increase in size. Energy stores are increased and the DNA is checked for any errors

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6
Q

What are the two parts of the mitotic phase? And what happens at each?

A

Mitosis - nucleus divides

Cytokinesis - cytoplasm divides

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7
Q

What is G0 phase?

A

When the cell leaves the cell cycle, either temporarily or permanently

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8
Q

Why would a cell go into G0 phase?

A
  • when a cell differentiates and becomes specialised
  • when there is damage to the DNA
  • the number of cells in G0 increases with age
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9
Q

What is the role of checkpoints in the cell cycle?

A

They monitor whether each phase has been completed correctly. This stops faulty DNA from being replicated

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10
Q

Where the three checkpoints in the cell cycle?

A

At the end of G1
At the end of G2 phase
At the point in mitosis where the the spindle fibres attach.

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11
Q

What happens at each checkpoint in the cell cycle?

A

G1 - if the cell passes the DNA is allowed to replicate. Checks correct proteins being produced etc.
G2 - checks the DNA for errors.
Mitosis - checks that the spindle fibres are correctly attached to the Chromosomes.

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12
Q

Define the term mitosis.

A

The process of the cell dividing. First the nucleus, then cytoplasm to produce two genetically identical daughter cells.

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13
Q

Define the term chromosome

A

A condensed form of chromatin - a DNA molecule.

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14
Q

Define the term centromere

A

The region joining two chromatids

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15
Q

Define the term sister chromatids

A

Two identical DNA molecules - chromosomes joined together

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16
Q

Define the term homologous pair

A

Two chromosomes that contain the same genes in the same loci

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17
Q

Describe how DNA is packaged in a chromosome

A

The DNA double helix is coiled and wrapped in loops around cores of the protein histone.

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18
Q

List the stages of mitosis in order

A

Prophase
Metaphase
Anaphase
Telophase

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19
Q

describe what happens in prophase of mitosis.

A
  • chromatin coils and condenses to form chromosomes. the nucleolus disappears and the nuclear membrane begins to break down.
  • protein microtubules form spindles linking the poles of the cell
  • two centrioles migrate to opposite poles of the cell
  • the spindle fibres attach to specific areas on the centromere and start to move the chromosomes to the centre of the cell.
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20
Q

describe what happens in metaphase of mitosis.

A

the chromosomes are moved by the spindle fibres to form a plane in the centre of the cell, called the metaphase plate.

21
Q

describe what happens in anaphase of mitosis.

A
  • the centromeres holding sister chromatids together divide, the chromatids are pulled to opposite ends of the cell by the spindle fibres.
  • the v shape of the chromatids is due to them being dragged through the cytosol.
22
Q

describe what happens in telophase of mitosis.

A
  • the chromatids have reached the poles and are now called chromatids
  • the two new sets of chromosomes assemble at each pole and a new nuclear membrane begins to form around each one.
  • the chromosomes start to uncoil and the nucleolus is formed.
23
Q

describe the process of cytokinesis in animal cells

A

a cleavage furrow forms around the middle of the cell. the cell surface membrane is pulled inwards by the cytoskeleton until it is close enough to fuse in the middle creating two cells.

24
Q

describe the process of cytokinesis in plant cells

A

vesicles from the golgi apparatus begin to assemble in the same area as the metaphase plate. the vesicles fuse with each other and the cell surface membrane dividing the cell into two. new sections of the cell wall then form along the cell membrane.

25
Q

how can mitotic index be calculated?

A

mitotic index = number of cells in mitosis/ total number of visible cells.

26
Q

why is mitotic division important?

A
  • necessary when all daughter cells have to be identical - growth, replacement and repair of tissues, also asexual reproduction.
27
Q

define the term diploid

A

when a cell has the full amount of DNA - two chromosomes of each type

28
Q

define the term haploid

A

when a cell has half the amount of DNA

29
Q

define the term gamete

A

a sex cell (haploid)

30
Q

define the term zygote

A

a fertilised egg - or when two gametes have fused to create a diploid cell.

31
Q

define the term meiosis

A

the form of cell division that produces gametes - four non genetically identical daughter cells.

32
Q

define the term reduction division

A

each gamete contains half of the chromosome number of the parent cell.

33
Q

explain the role of meiosis in life cycles.

A

meiosis creates haploid gametes which are essential for sexual reproduction. two gametes fuse to make a zygote.

34
Q

state two ways in which meiosis produces variation.

A
  • crossing over of alleles

- random alignment of bivalents and homologous chromosomes.

35
Q

define the term bivalent

A

a pair of homologous chromosomes

36
Q

define the term crossing over

A

when chromosomes are moved through the cytosol they entangle with each other and some alleles end up being a part of a different chromosome.

37
Q

define the term chiasma

A

the point at which the chromosomes break and rejoin after the process of crossing over.

38
Q

define the term recombinant chromatid

A

a chromatid that has DNA from another chromatid after crossing over. they willnow have a different combination of alleles.

39
Q

define the term random independent assortment.

A

in metaphase 1 the maternal and paternal chromosomes may end up facing either pole of the cell. this is random organisation that causes genetic variation.

40
Q

state the stages of meiosis in order.

A 
MEIOSIS 1:
- prophase 1
- metaphase 1
- anaphase 1
- telophase 1
MEIOSIS 2:
- prophase 2
- metaphase 2
- anaphase 2
- telophase 2
41
Q

describe what happens in prophase 1 of meiosis.

A
  • chromosomes condense, the nuclear envelope disintegrates, the nucleolus disappears and the spindle formation begins.
  • the difference between mitosis and meiosis is that here the homologous chromosomes are paired to form bivalents. when they are bought together crossing over occurs.
42
Q

describe what happens in metaphase 1 of meiosis.

A
  • homologous pairs of chromosomes line up on the metaphase plate.
  • this is where random independent assortment occurs - maternal and paternal chromosomes face in random directions producing genetic variation.
43
Q

describe what happens in anaphase 1 of meiosis.

A
  • chromosomes are pulled to opposite poles but chromatids stay joined together.
  • sections of the DNA that became entangled during crossing over now break off and rejoin at the chiasmata - causing genetic variation.
  • this has formed recombinant chromatids!
44
Q

describe what happens in telophase 1 of meiosis.

A
  • the chromosomes assemble at each pole and the nuclear membranes reform
  • chromosomes uncoil
  • the cell undergoes cytokinesis to create two cells. the cell is now haploid.
45
Q

describe what happens in prophase 2 of meiosis.

A

the chromosomes which still consist of two chromatids condense and become visible again. the nuclear envelope breaks down and spindle formation begins.

46
Q

describe what happens in metaphase 2 of meiosis.

A

the individual chromosomes assemble on the metaphase plate as in mitosis. independent assortment again occurs as the chromosomes are no longer identical due to crossing over, so the alleles may end up facing either pole.

47
Q

describe what happens in anaphase 2 of meiosis.

A

the chromatids of the individual chromosomes are divided at the centromere and pulled to opposite poles of the cell.

48
Q

describe what happens in telophase 2 of meiosis.

A

the chromatids assemble at the poles of the cell. the chromosomes uncoil an the nuclear envelope reforms. the nucleolus becomes visible.
cytokinesis divides each cell to produce four haploin genetically unidentical daughter cells.

biology (22 decks)

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