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HKDSE Biology > 11: Cell Cycle and Division > Flashcards

11: Cell Cycle and Division Flashcards

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1
Q

What is mitotic cell division?

A

Mitotic cell division is a cell division process in which one parent cell divides into two daughter cells.

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2
Q

How is genetic information stored inside the cell?

A

Genetic information is carried in deoxyribonucleic acid (DNA). Inside the nucleus, DNA molecules coil around some proteins to form chromosomes.

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3
Q

What are the characteristics of chromatin and their advantages?

A

Chromatin are fibres containing DNA and protein molecules in a dispersed form. This structure allows DNA to be replicated, genetic information to be read, and proteins to be synthesised.

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4
Q

What are the similarities and differences between chromosomes and chromatin?

A

Similarities: both contain DNA and protein molecules. / both store genetic information.
Differences: chromatin are less compact / more disperse while chromosomes are shorter, thicker, and more compact. Chromosomes are more highly coiled than chromatin.

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5
Q

What is the advantage of the compact structure of chromosomes?

A

In this form, chromosomes can be moved into the daughter cells more easily without tangling during cell division.

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6
Q

How many DNA molecules does a chromosome in duplicated state contain?

A

2

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7
Q

What are the similarities and differences between a chromosome in duplicated state and a chromosome not in duplicated state?

A

Similarity: Both types of chromosome have one centromere.
Difference: a chromosome in duplicated state contains two DNA molecules stored in two genetically identical sister chromatids, while a chromosome not in duplicated state only contains 1 DNA molecule.

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8
Q

What is the difference between the two sister chromatids on one chromosome in duplicated state and two chromosomes not in duplicated state?

A

The two sister chromatids share one centromere and are collectively called “one chromosome (in duplicated state), while the two chromosomes have two centromeres. / After the separation of sister chromatids, the two chromatids are called chromosomes.

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9
Q

How many chromosomes do humans have in our somatic cells?

A

46

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10
Q

What are the characteristics of homologous chromosomes?

A
  1. The two members in each pair have the same size and shape (except for pair 23 in males).
  2. One of them, called the paternal chromosome, comes from the male parent. The other, called the maternal chromosome, comes from the female parent.
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11
Q

What is the difference between diploid and haploid cells?

A

Diploid cells contain two sets of chromosomes (2n). They contain both members of each homologous pair of chromosomes. The body cells / somatic cells of most organisms are diploid.
Haploid cells contain one set of chromosomes (n). They only contain one member of each homologous pair. The sex cells / gametes are haploid.

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12
Q

Is there relationship between the number of chromosomes and the complexity of the organism?

A

no

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13
Q

What is the cell cycle?

A

The cell cycle is a sequence of events that take place from the time a cell is formed from its parent cell until its own division into two cells.

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14
Q

Why do cells need to divide?

A

As a cell grows, the surface area to volume ratio decreases. As a result, there is slower exchange of materials and higher rate of consumption of nutrients + production of waste. This is inefficient as the cell cannot obtain enough nutrients and there will be a lot of waste accumulated. Dividing increases the surface area to volume ratio again to restore the efficiency of the cells.

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15
Q

What are the names of 5 stages in the cell cycle?

A

interphase: G1 phase, S phase, G2 phase
mitotic cell division: mitosis, cytokinesis

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16
Q

What are the key events happening in the G1 phase in interphase of mitotic cell division?

A

Organelles and proteins and synthesised.

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17
Q

What are the key events happening in the S phase in interphase of mitotic cell division?

A

The genetic material is synthesised and replicated, the centromere is synthesised.

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18
Q

What are the key events happening in the G2 phase in interphase of mitotic cell division?

A

The cell grows to maximum size and organelles and proteins continue to be synthesised.

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19
Q

What are the key events happening in the interphase of mitotic cell division?

A

The cell carries out its functions within the organism. It also synthesises proteins, produce new organelles, grows to maximum size, and carries out DNA replication to prepare for cell division.

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20
Q

List 2 types of cells that cannot undergo mitotic cell division.

A

neurones, red blood cells

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21
Q

What is the difference between mitotic cell division and mitosis?

A

Mitotic cell division refers to the whole process of a parent cell dividing to form two daughter cells, which includes mitosis and cytokinesis. Mitosis specifically refers to the nuclear division taking place in mitotic cell division.

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22
Q

What are the properties of the daughter cells formed from mitotic cell division?

A

They are genetically identical.

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23
Q

What are the names of the 4 stages of mitosis?

A

prophase, metaphase, anaphase, telophase

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24
Q

How can a cell in interphase be identified in a light microscope?

A

the chromosomes are not visible, existing as a mass of fibres (chromatin).

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25
Q

What are the key events taking place in the prophase of mitosis?

A

Chromosomes (in their duplicated state) shorten and thicken, becoming visible. The nuclear membrane breaks down.

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26
Q

What are the key events taking place in the metaphase of mitosis?

A

Chromosomes (in their duplicated state) line up in single file in the middle of the cell on the equator. Spindle fibres attach to the chromosomes.

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27
Q

What are the key events taking place in the anaphase of mitosis?

A

The spindle fibres contract, separating sister chromatids, which move to opposite poles of the cell. The cytoplasm starts to divide.

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28
Q

What are the key events taking place in the telophase of mitosis?

A

A new nuclear membrane forms around each group of chromosomes (previously sister chromatids). The chromosomes uncoil to become chromatin again.

29
Q

What are the key events taking place in cytokinesis of animal cells?

A

The cell membrane constricts inward to split the cytoplasm into two equal halves. The cell splits into two.

30
Q

What are the key events taking place in cytokinesis of plant cells?

A

The cell plate made up of new cell membranes and cell walls is formed and grows outwards to split the cytoplasm into two equal halves. The cell splits into two.

31
Q

What is the importance of mitotic cell division?

A

Mitotic cell division produces daughter cells that are genetically identical to their parent cell. They have the same structure and perform the same functions as the parent cell. It is important for growth, repair and asexual reproduction.

32
Q

Why do humans produce haploid gametes?

A

Humans carry out sexual reproduction and produce haploid gametes, which fuse together during fertilisation to form a single cel called a zygote.

33
Q

How are gametes made haploid?

A

They are produced by gamete-producing cells in reproductive organs, which carry out meiotic cell division to produce haploid gametes.

34
Q

Are all cells in reproductive organs haploid?

A

No, the cells making up the organs themselves and gamete-producing cells are diploid.

35
Q

What are the names of the 5 stages taking place in meiotic cell division?

A

interphase, meiosis I, cytokinesis, meiosis II, cytokinesis

36
Q

What is the significance of meiosis I?

A

It involves the pairing and separation of homologous chromosomes, reducing the chromosome number by half, producing 2 haploid daughter cells with chromosomes in duplicated state.

37
Q

What is the significance of meiosis II?

A

It involves the separation of sister chromatids of each chromosome in duplicated state, producing 4 haploid daughter cells with chromosomes not in duplicated state.

38
Q

What are the names of the 4 stages of meiosis I?

A

prophase I, metaphase I, anaphase I, telophase I

39
Q

What are the names of the 4 stages of meiosis II?

A

prophase II, metaphase II, anaphase II, telophase II

40
Q

What are the key events taking place in the prophase of meiosis I?

A

Chromosomes (in their duplicated state) shorten and thicken, becoming visible. Homologous chromosomes pair up and crossing over may occur. The nuclear membrane breaks down.

41
Q

What are the key events taking place in the metaphase of meiosis I?

A

Homologous chromosomes (in their duplicated state) line up in pairs in the middle of the cell on the equator. Spindle fibres attach to the chromosomes.

42
Q

What are the key events taking place in the anaphase of meiosis I?

A

The spindle fibres contract, separating the two members of each homologous pair, which move to opposite poles of the cell. The cytoplasm starts to divide.

43
Q

What are the key events taking place in the telophase of meiosis I?

A

A new nuclear membrane forms around each group of chromosomes. The chromosomes uncoil to become chromatin again.

44
Q

What are the features of the cells after meiosis I and cytokinesis?

A

Two haploid daughter cells with chromosomes in duplicated state are formed.

45
Q

What are the key events taking place in the prophase of meiosis II?

A

Chromosomes (haploid number, in their duplicated state) shorten and thicken, becoming visible. The nuclear membrane breaks down again.

46
Q

What are the key events taking place in the metaphase of meiosis II?

A

Chromosomes (haploid number, in their duplicated state) line up in single file in the middle of the cell on the equator. Spindle fibres attach to the chromosomes.

47
Q

What are the key events taking place in the anaphase of meiosis II?

A

The spindle fibres contract, separating sister chromatids, which move to opposite poles of the cell. The cytoplasm starts to divide.

48
Q

What are the key events taking place in the telophase of meiosis II?

A

A new nuclear membrane forms around each group of chromosomes (previously sister chromatids). The chromosomes uncoil to become chromatin again.

49
Q

What are the features of the daughter cells after meiotic cell division?

A

Four haploid daughter cells are formed.

50
Q

What is the importance of producing haploid gametes in meiotic cell division?

A

When two haploid gametes fuse during fertilisation to form a zygote, the diploid number of chromosomes is restored, allowing the species to preserve a constant number of chromosomes from generation to generation.

51
Q

What are two ways genetic variation can be produced among daughter cells?

A

Independent assortment of chromosomes and crossing over during meiotic cell division.

52
Q

What is the importance of genetic variation in a species?

A

Genetic variations among individuals of the same species increase the chance for the species to survive when environmental conditions change.

53
Q

How is genetic variation created through independent assortment?

A

During metaphase I, pairs of homologous chromosomes line up randomly along the equator of the cell. Members of each homologous chromosome pair then separate independently of the other pairs. This produces various genetic combinations in the gametes. For humans having 23 pairs of chromosomes, the number of possible combinations is 223, which is very large.

54
Q

How is genetic variation created through crossing over?

A

During prophase I, exchanges of the corresponding segments of non-sister chromatids of a pair of homologous chromosomes may occur. The non-sister chromatids wrap around each other, forming a x-shaped structure called chiasma (chiasmata). The chromatids break, exchange the corresponding segments, and rejoin. This creates new genetic combinations in the gametes.

55
Q

Is crossing over rare?

A

no

56
Q

What are the common events taking place in prophase of mitosis and prophase I and II of meiosis?

A

The nuclear membrane breaks down, chromatin fibres condense to form chromosomes (in duplicated state).

57
Q

What is the difference between prophase of mitosis and prophase II of meiosis II?

A

There is a diploid number of chromosomes in prophase of mitosis, but only a haploid number of chromosomes in prophase II.

58
Q

What is the difference between prophase of mitosis and prophase I of meiosis I?

A

Chromosomes do not pair up in prophase of mitosis, while homologous chromosomes pair up in prophase I. Crossing over may occur in prophase I but not in prophase of mitosis.

59
Q

What are the differences between prophase I and prophase II of meiosis I and II?

A

Chromosomes do not pair up in prophase II, while homologous chromosomes pair up in prophase I. Crossing over may occur in prophase I but not in prophase II.
There is a diploid number of chromosomes in prophase I, but only a haploid number of chromosomes in prophase II.

60
Q

What is the difference between metaphase of mitosis and metaphase II of meiosis II?

A

Both members of homologous chromosome pairs line up along the equator in metaphase of mitosis, but only one member of each homologous chromosome pair line up along the equator in metaphase II.

61
Q

What is the difference between metaphase of mitosis and metaphase I of meiosis I?

A

Chromosomes do not pair up and line up in single file in metaphase of mitosis, while homologous chromosomes pair up and line up in pairs in metaphase I.

62
Q

What are the differences between metaphase I and metaphase II in meiosis I and II?

A

Chromosomes do not pair up in metaphase II, while homologous chromosomes line up in pairs in metaphase I. There is a diploid number of chromosomes in metaphase I, but only a haploid number of chromosomes in metaphase II.

63
Q

What is the similarity between metaphase of mitosis and metaphase II of meiosis II?

A

Chromosomes (in duplicated state) line up in single file along the equator.

64
Q

What is the similarity between metaphase of mitosis and metaphase II of meiosis II?

A

Chromosomes (in duplicated state) line up in single file along the equator.

65
Q

What is the similarity between anaphase of mitosis and anaphase II of meiosis II?

A

Both involve the separation of sister chromatids and the splitting of the centromere.

66
Q

What is the significance of the pairing of homologous chromosomes occurring in the first meiotic cell division but not in mitotic cell division?

A

During pairing of homologous chromosomes, crossing over may occur with the exchange of genetic segments between the non sister chromatids that produces new combinations of genes, increasing genetic variation.

67
Q

What is the significance of independent assortment of homologous chromosomes in pairs along the equator occurs in meiotic cell division (metaphase I) but not in mitotic cell division?

A

This results in random separation of the homologous chromosomes that produces different combination of genes in the gametes, increasing genetic variations.

68
Q

What is the significance of separating chromosomes from their homologous pairs in meiotic cell division but not in mitotic cell division?

A

This ensures that each daughter cell’s number of chromosomes is reduced to half, containing a haploid number of chromosomes.

69
Q

What is the significance of two nuclear divisions in meiotic cell division?

A

To ensure the production of haploid gametes so that the diploid condition of genetic material can be restored at fertilisation to form the zygote.

HKDSE Biology (22 decks)

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