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🧬 > Topic 6: Cell Cycle And Division > Flashcards

Topic 6: Cell Cycle And Division Flashcards

1
Q

What is mitotic cell division?

A

Mitotic cell division is a process in which a cell (parent cell) divides to form new cells (daughter cells).

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2
Q

Why is cell division important?

A

It involves the passing on of genetic information from parent cells to daughter cells.
This information determines the structure and functions of the cells and is carried in DNA.

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3
Q

What is a centromere?

A

A centromere is the junction between two sister chromatids of the same chromosome.

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4
Q

What are sister chromatids?

A

When a cell is not dividing, individual chromosomes are not visible. They exist as a mass of long thin fibres called chromatins.
When cell division begins, the chromatin fibres coil up tightly. Each chromosome is seen to consist of two identical chromatids called sister chromatids.

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5
Q

What are chromosomes?

A

Inside the nucleus, DNA and proteins together form structures called chromosomes.

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6
Q

What are the properties of chromosomes?

A
  1. They exist in pairs called homologous chromosomes in body cells.
  2. One member in a homologous pair comes from the male parent (paternal chromosome), and the other from the mother (maternal chromosome).
  3. A body cell that has 2 sets of chromosomes is a diploid, and 1 set of chromosomes a haploid.
  4. Number of chromosomes are the same among individuals of the same species but different among different species.
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7
Q

What is a cell cycle?

A

A cell cycle is the sequence of events that takes place in a body from one cell division to the next.

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8
Q

Mitotic cell division only occurs in __________.

A

Body cells

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9
Q

Stages of mitotic cell division?

A
  1. Interphase (cell growth)
  2. Mitotic cell division:
    Nuclear division:
    a. Prophase
    b. Metaphase
    c. Anaphase
    d. Telophase (Cytoplasmic division)
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10
Q

Interphase

The cell is very active and still carries out its functions!

A

Prepare for cell division
2. 1. Active phase: synthesis of new organelles and proteins
2. DNA replicates.
3. Each chromosome becomes duplicated and consists of 2 identical DNA molecules.
a. Sister chromatids: n to 2n
b. DNA: x to 2x
c. chromosomes: 2n to 2n
4. Cell grows to its maximum size
5. Chromosomes are invisible at this stage.
6. The nuclear membrane or nucleus is present.

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11
Q

Properties of mitotic cell division

A
  1. A body cell divides to form two daughter cells.
  2. The daughter cell contains the same number and kind of chromosomes as their parent cell. They are genetically identical.
  3. Involves both nuclear and cytoplasmic division.
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12
Q

Stages of nuclear division

A
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
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13
Q

What is nuclear division?

A

It is called mitosis. It involves the separation of sister chromatids of each chromosomes and the equal distribution of chromatids between two daughter nuclei.

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14
Q

Stages of mitotic cell division

A
  1. Mitosis (nuclear division)
  2. Cytoplasmic division
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15
Q

Prophase

A
  1. Chromosomes shorten and thicken. They become visible.
  2. The nuclear membrane breaks down.
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16
Q

Metaphase

A
  1. The chromosomes line up along the equator.
  2. Spindle fibres attach to the chromosomes.
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17
Q

Anaphase

A
  1. The spindle fibres contract.
  2. Sister chromatids separate and move to opposite poles of the cell.
  3. The cytoplasm starts to divide.
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18
Q

Telophase

A
  1. New nuclear membranes form around each group of chromosomes.
  2. The chromosome uncoil to become chromatin again.
19
Q

What is cytoplasmic division?

A

It is called cytokinesis. The cytoplasm of a parent cell divides into two equal halves, forming two daughter cells.

20
Q

Properties of cytoplasmic division

A

In animal cells, the cell membrane around the centre of the cell constricts inwards until the cell separates into two.
In plant cells, a cell plate is formed between the two daughter nuclei. It grows outwards from the centre of the cell, dividing the cell into two halves.

21
Q

The importance of mitotic cell division?

A
  1. Growth: provides new cells for growth
  2. Repair: provides new cells to replace worn out cells or repair damaged tissues
  3. Asexual reproduction: produces offspring genetically identical to their parents e.g. potatoes
22
Q

What is meiotic cell division?

A

Meiotic cell division occurs only in gamete-producing cells and results in the formation of zygote.

23
Q

Properties of meiotic cell division

A

Meiotic cell division reduces the chromosome number by half. It gives rise to 4 haploid daughter cells which are genetically different from the parent cell and among themselves.

24
Q

Stages of meiotic cell division

A

1st meiotic division:
1. Interphase
2. Nuclear division
3. Cytoplasmic division

2nd meiotic division:
1. Interphase (with no DNA replication)
2. Nuclear division
3. Cytoplasmic division

25
Q

Prophase I

A
  1. Chromosomes shorten, thicken and become visible.
  2. Members of each homologous pair pair up.
  3. The nuclear membrane breaks down.
26
Q

Metaphase I

A
  1. Homologous pairs line up along the equator.
  2. Spindle fibres attach to the chromosomes.
27
Q

Anaphase I

A
  1. The spindle fibres contract.
  2. The two members of each pair of homologous chromosomes move to opposite sides of the cell.
  3. The cytoplasm starts to divide.
28
Q

Telophase I

A

New nuclear membranes form around each group of chromosomes.

Chromosomes don’t uncoil!
Haploid cells are already formed!

29
Q

Prophase II

A

The nuclear membrane breaks down again.

30
Q

Metaphase II

A
  1. Chromosomes line up along the equator.
  2. New spindle fibres attach to the chromosomes.
31
Q

Anaphase II

A
  1. The spindle fibres contract.
  2. The sister chromatids separate and move to opposite poles of the cells.
  3. The cytoplasm starts to divide.
32
Q

Telophase II

A
  1. New nuclear membranes form around each group of chromosomes.
  2. The chromosomes uncoil to become chromatin again.
33
Q

The importance of meiotic cell division?

A
  1. Producing haploid gametes
  2. Producing genetic variations in gametes
34
Q

Producing haploid gametes

A
  • produces haploid gametes for sexual reproduction
  • the male and female gamete fuse at fertilisation to form a zygote, the diploid number of chromosome can be restored.
35
Q

Producing genetic variations in gametes

A

Genetic variations within a species increase the chance of the species to survive when environmental conditions change.
Genetic variations are produced by the independent assortment of chromosomes and crossing over during meiotic cell division.

36
Q

Independent assortment of chromosomes

A

Pairs of homologous chromosomes line up along the equator of the cell.
The members of each homologous pair separate independently of the other pairs of the chromosomes.

37
Q

When does the independent assortment of chromosomes occur?

A
  1. in metaphase I, when the pairs of homologous chromosomes are arranged along the equator
  2. in metaphase II, the sister chromatids separate to form new combinations
38
Q

Crossing over

A

It is an exchange of corresponding segments of non-sister chromatids.
During prophase I, homologous pair up.
Non-sister chromatids wrap around each other, forming a chiasma.
At the chiasma, the chromatids break, exchange and rejoin.

39
Q

What is a gene?

A

A gene is a segment of DNA that contains a feature

40
Q

What is an allele?

A

A version of a gene.

41
Q

Similarities between Mitotic and Meiotic cell division?

A
  1. DNA is replicated during the first interphase.
  2. Both involve nuclear division and cytoplasmic division.
  3. Both involvement the movement and distribution of chromosomes among daughter cells.
42
Q

What are the differences in the processes of mitotic and meiotic cell division?

A
  1. Number of cell divisions: meiosis x 2, mitosis x 1.
  2. Pairing of homologous chromosomes: only meiosis.
  3. Crossing over and independent assortment: only meiosis.
  4. Number of cells produced: meiosis x 4, mitosis x 2
43
Q

What are the differences in daughter cells of meiosis and mitosis?

A
  1. Number of cells produced: meiosis x 4, mitosis x 2.
  2. Chromosome number: Mitosis same as parent cell, meiosis is half of parent cell.
  3. Cell type: body cells vs gametes
44
Q
A

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