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Biology: 2.1.6 Cellular Organisation > cellular division > Flashcards

cellular division Flashcards

(53 cards)

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1
Q

What are the two main phases of the eukaryotic cell cycle? (2)

A
  1. Interphase - Cells are not actively dividing and prepare for cell division.
  2. M (Mitotic) Phase - The period of cell division, including mitosis and cytokinesis.
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2
Q

What happens during interphase? (2)

A

Cell carries out normal functions;

Prepares for cell division

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3
Q

What are the three stages of interphase? (3)

A
  1. G1 Phase - Proteins are produced, and organelles replicate.
  2. S Phase - DNA is replicated, doubling the amount of DNA.
  3. G2 Phase - The cell increases in size, energy stores rise, and duplicated DNA is checked for errors.
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4
Q

What are the stages of the M phase? (2)

A
  1. Mitosis - Division of the nucleus.
  2. Cytokinesis - Division of the cytoplasm.
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5
Q

What is the G0 phase? (1)

A

Phase where the cell leaves the cycle, either temporarily or permanently.

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6
Q

What are reasons a cell enters the G0 phase? (3)

A
  1. Differentiation - The cell becomes specialized and can no longer divide.
  2. DNA Damage - If the DNA is damaged, the cell may enter G0 permanently.
  3. Senescence - Cells eventually stop dividing and become senescent. This increases with age and is linked to age-related diseases like cancer.
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7
Q

Why is it important to regulate the cell cycle? (2)

A

To ensure that two identical daughter cells are created from the parent cell;

To ensure the cell divides only when it has grown to the right size, the DNA is error-free, and chromosomes are in the correct positions during mitosis.

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8
Q

What are checkpoints in the cell cycle? (1)

A

Control mechanisms that ensure the cell cycle proceeds correctly.

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9
Q

What does the G1 checkpoint check for? (4)

A

Cell size;
Nutrients;
Growth factors;
DNA damage

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10
Q

What happens if the cell passes the G1 checkpoint? (2)

A

DNA replication is triggered;

The cell enters the S phase.

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11
Q

What happens if the cell doesn’t meet the requirements of the G1 checkpoint? (1)

A

The cell enters the G0 phase.

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12
Q

What does the G2 checkpoint check for? (3)

A

Cell size;
DNA replication;
DNA damage

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13
Q

What happens if the cell passes the G2 checkpoint? (1)

A

The cell initiates mitosis (M phase).

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14
Q

What does the spindle assembly checkpoint check for? (1)

A

Checks whether all chromosomes are attached to spindle fibers and aligned.

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15
Q

What happens if the spindle assembly checkpoint is passed? (1)

A

Mitosis proceeds to completion.

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16
Q

What happens during prophase? (4)

A
  1. Chromosomes condense and shorten.
  2. Nucleolus disappears.
  3. Centrioles move towards cell ends, forming spindle fibers.
  4. Nuclear envelope breaks down, and chromosomes lie free in the cytoplasm.
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17
Q

What happens during metaphase? (2)

A
  1. Chromosomes line up in the middle of the cell and attach to spindle fibers via their centromere.
  2. A metaphase plane is formed in the center of the cell.
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18
Q

What happens during anaphase? (2)

A
  1. Centromeres divide, separating sister chromatids.
  2. Spindles contract, pulling chromatids to opposite ends of the cell, giving them a v-shape.
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19
Q

What happens during telophase? (3)

A
  1. Chromatids uncoil and become chromosomes again.
  2. Nuclear envelope forms around each set of chromosomes, creating two nuclei.
  3. Nucleolus reappears.
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20
Q

What happens during cytokinesis? (2)

A
  1. The cytoplasm divides.
  2. Creating two genetically identical diploid daughter cells.
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21
Q

What type of cells are produced by mitosis? (1)

A

Two genetically identical diploid cells (each with two copies of each chromosome).

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22
Q

How does cytokinesis differ in plant cells? (3)

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A
  1. Vesicles from the Golgi apparatus assemble at the metaphase plate location.
  2. Vesicles fuse with each other and the cell surface membrane, dividing the cell in two.
  3. New sections of the cell wall form along the new membrane.
23
Q

How can chromosomes be observed in plant cells under a microscope? (2)

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A

Chromosomes can be stained with a dye like toluidine blue O; To make them visible.

24
Q

Why is mitosis necessary? (3)

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A
  1. Growth - development of organism.
  2. Tissue repair - to replace damaged or dead cells.
  3. Asexual reproduction.
25
How do prokaryotic organisms (e.g., bacteria) divide? (1)
By binary fission.
26
What is the significance of meiosis? (2)
1. Occurs in sexually reproducing organisms to produce gametes. 2. It results in 4 genetically different, haploid daughter cells.
27
What is the difference between haploid and diploid cells? (2)
Diploid = Contains 2 copies of each chromosome; Haploid: Contains 1 copy of each chromosome.
28
What type of cells are produced by meiosis? (2)
4 genetically different; Haploid daughter cells.
29
Why is meiosis important for sexual reproduction? (2)
1. Meiosis produces haploid cells. 2. When fertilization occurs, the diploid number is restored.
30
What are homologous chromosomes? (3)
1. Pair of chromosomes. 2. One maternal and one paternal. 3. Same size and have the same genes at the same loci but may have different alleles.
31
What are sister chromatids? (2)
1. Identical copies of each other formed during DNA replication. 2. They remain connected at the centromere until separated during cell division.
32
What is the difference between homologous chromosomes and sister chromatids? (2)
1. Homologous chromosomes are not identical and may have different alleles. 2. Sister chromatids are identical copies of a duplicated chromosome.
33
What happens before meiosis starts? (2)
1. DNA unravels and replicates, producing two copies of each chromosome. 2. DNA condenses to form double-armed chromosomes, each consisting of two sister chromatids joined by a centromere.
34
What happens in the first division of meiosis (meiosis I)? (2)
1. Homologous pairs of chromosomes are separated, halving the chromosome number. 2. Independent segregation occurs, creating random combinations of chromosomes in each daughter cell.
35
What happens during prophase I of meiosis? (4)
1. Chromosomes condense and arrange into homologous pairs. 2. Crossing-over occurs. 3. Centrioles move to opposite poles, forming spindle fibers. 4. The nuclear envelope breaks down.
36
What happens during metaphase I of meiosis? (3)
1. Homologous pairs line up at the center of the cell and attach to spindle fibers by their centromeres. 2. Independent assortment occurs, where the orientation of each homologous pair is random. 3. Leading to a mix of maternal and paternal chromosomes at either pole.
37
What happens during anaphase I of meiosis? (2)
1. Spindles contract, separating homologous pairs. 2. One chromosome from each pair moves to opposite ends of the cell.
38
What happens during telophase I of meiosis? (2)
1. Chromosomes uncoil. 2. The nuclear envelope forms around each group of chromosomes.
39
What happens during cytokinesis after meiosis I? (2)
1. The cytoplasm divides. 2. Resulting in two haploid daughter cells.
40
What happens during the second division of meiosis (meiosis II)? (4)
1. Pairs of sister chromatids are separated. 2. The centromeres are divided. 3. Producing 4 haploid daughter cells (gametes). 4. That are genetically different from each other.
41
What happens during prophase II of meiosis? (3)
1. Chromosomes, still consisting of two sister chromatids, condense and become visible. 2. The nuclear envelope breaks down. 3. Spindle formation begins.
42
What happens during metaphase II of meiosis? (1)
Individual chromosomes (not homologous pairs) assemble on the metaphase plate.
43
What happens during anaphase II of meiosis? (2)
1. Sister chromatids are separated and pulled to opposite poles after division of the centromeres. 2. Just like in anaphase of mitosis.
44
What happens during telophase II of meiosis? (2)
1. Chromosomes uncoil. 2. The nuclear envelope reforms, and the nucleolus becomes visible.
45
What happens during cytokinesis after meiosis II? (2)
1. The cytoplasm divides. 2. Producing 4 genetically different haploid daughter cells.
46
Why are the daughter cells produced in meiosis genetically different? (1)
Due to crossing over and independent assortment during meiosis.
47
What are two ways meiosis leads to genetic variation? (2)
1. Crossing over. 2. Independent segregation.
48
How does random fertilization contribute to genetic variation? (2)
1. Any sperm can fuse with any egg. 2. Which increases genetic variation within a species.
49
What is crossing-over and how does it lead to genetic variation? (4)
1. Homologous chromosomes come together during meiosis. 2. Chromatids twist and swap parts. 3. The chromatids contain different combinations of alleles. 4. Each daughter cell gets chromosomes with unique allele combinations.
50
What is independent assortment and how does it lead to genetic variation? (3)
1. When homologous chromosomes are separated in meiosis I. 2. Which chromosome from each pair ends up in each daughter cell is random. 3. This results in daughter cells with different combinations of alleles.
51
How is meiosis different from mitosis? (3)
1. Meiosis produces cells with half the number of chromosomes, while mitosis produces cells with the same number as the parent cell. 2. Meiosis produces genetically different daughter cells, while mitosis produces genetically identical cells. 3. Meiosis produces 4 daughter cells, while mitosis produces 2 daughter cells.
52
Why do meiosis and mitosis produce different outcomes? (2)
1. Mitosis involves one division, while meiosis involves two divisions. 2. Mitosis does not involve crossing-over or independent segregation, so daughter cells are genetically identical.
53
How do you calculate the number of possible combinations of chromosomes for each daughter cell in meiosis? (2)
2ⁿ; Where n is the number of pairs of homologous chromosomes (haploid number).

Biology: 2.1.6 Cellular Organisation (3 decks)

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