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IP Secondary 4 Biology > Chapter 6 - Cell Division > Flashcards

Chapter 6 - Cell Division Flashcards

1
Q

Growth is accompanied by ________ and ________ to form tissues and organs

A

cell division

differentiation

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2
Q

Compare growth in plants and animals

A

Plant: Growth is restricted to growing points (the tips of shoots and roots)
Animals: Growth occurs throughout the body
–
Plant: Growth occurs throughout the life of the plant
Animals: Growth stops after a certain age (when the animal reaches maturity)

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3
Q

Compare mitosis and meiosis

A

Mitosis: Involved in growth and development
Meiosis: Involved in reproduction
–
Mitosis: Produces genetically identical cells
Meiosis: Produces genetically varied cells (gametes)

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4
Q

What is mitosis?

A

A type of nuclear division that results in the production of two daughter nuclei which are genetically identical to the parent

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5
Q

After mitosis, how many chromosomes will the daughter nuclei have?

A

The same number of chromosomes as the parent nucleus

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6
Q

Overview of mitosis

A

Parent cell → DNA replicates → mitosis → 2 genetically identical daughter cells

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7
Q

What are the stages of the cell cycle?

A
  1. Interphase (resting stage)
  2. Mitosis (nuclear division)
  3. Cytokinesis (division of the cytoplasm)
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8
Q

Interphase is also known as the ________ or ________ stage

A

‘resting’

non-dividing

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9
Q

What do the cells do during interphase?

A

Absorb nutrients
Build up protoplasm
Synthesise new organelles
Replicate DNA

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10
Q

What happens just before the cell enters the nuclear division phase?

A

The chromatin threads replicate

The centrioles replicate and divide

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11
Q

How does DNA replicate (describe the entire process)?

A
  1. The chromatin thread replicates to produce two identical chromatin threads
  2. These chromatin threads coil and shorten to become chromosomes
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12
Q

Each chromosome consist of two identical DNA molecules known as ________

A

sister chromatids

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13
Q

The sister chromatids are joined at a point known as the ________

A

centromere

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14
Q

Why must DNA replication and mitosis be precisely controlled?

A

To ensure that all daughter cells are genetically stable

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15
Q

What would happen if an error occurs during replication?

A

Gene mutation

  • The new DNA strand formed would be different from the original
  • This is passed on to the daughter cell
  • Some forms of gene mutation may lead to uncontrolled division of cells (cancer), which may be fatal
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16
Q

What are the stages of mitosis?

A
  1.  Prophase
  2.  Metaphase
  3.  Anaphase
  4. Telophase
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17
Q

What happens during early prophase?

A

In an animal cell

  1. Asters form around the centrioles
  2. The two pairs of centrioles move apart to opposite poles of the cell
  3. The nucleolus disappears
  4. Chromatin condense, coil and shorten to become chromosomes
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18
Q

What does each chromosome consist of?

A

Consists of two sister chromatids attached at the centromere

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19
Q

How do chromosomes look like under the microscope?

A

Appear as X-shaped structures

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20
Q

What happens during late prophase?

A
  1. The nuclear envelope disappears

2. A spindle forms with the spindle fibres extending from one pole of the cell to the other

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21
Q

What happens during metaphase?

A
  1. Chromosomes line up singly along the equator of the spindle
  2. The centromere of each chromosome is attached to a spindle fibre
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22
Q

What happens during anaphase?

A
  1. Each centromere divides

2. The spindle fibres pull the sister chromatids apart to opposite poles of the cell (become daughter chromosomes)

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23
Q

What happens during telophase?

A
  1. Spindle fibres disintegrate
  2. A nuclear envelope forms around each set of chromosomes
  3. A nucleolus forms inside each nucleus
  4. Chromosomes uncoil and lengthen into thread-like structures (chromatin)
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24
Q

What is cytokinesis?

A

The division of the cytoplasm

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25
Q

What happens during cytokinesis?

A

In animal cells

1. Furrows form, deepen and eventually split the cell into two

26
Q

Characteristics of mitosis in plant cells

A

Centrioles are absent
Cleavage of cytoplasm does not occur during cytokinesis
A cell plate forms between two daughter nuclei by fusion of fluid-filled vesicles

27
Q

Characteristics of mitosis in animal cells

A

Centrioles are present

Cleavage of cytoplasm occurs during cytokinesis (formation of furrows)

28
Q

What is the importance of mitosis?

A

To produce genetically identical cells

29
Q

What is the production of genetically identical cells (mitosis) required for?

A

Growth of an organism
Repair of worn-out parts of tissue, wound healing and replacement of dead cells
Asexual reproduction in plants such as the development of shoots and roots in storage organs (i.e. rhizomes and bulbs)

30
Q

What is meiosis?

A

A type of nuclear division that results in the production of four daughter
nuclei, each containing half the number of chromosomes as the parent cells

31
Q

Why are gametes produced?

A

In fertilisation, when the nucleus of the male gamete fuses with the nucleus of the female gamete to form a zygote, a diploid
number of chromosomes is maintained in the zygote

32
Q

Overview of meiosis

A

1 diploid parent cell with 2 pairs of chromosomes → Replication of chromosomes → Each daughter cell contains 2 chromosomes, each consisting of 2 chromatids → 4 haploid gametes, each containing 2 chromosomes

33
Q

What happens during interphase?

A

Chromatin threads replicate to produce two identical sister chromatids
The centrioles divide

34
Q

What happens during prophase I?

A
  1. Chromatin threads condense, coil and shorten into visible chromosomes
  2. Synapsis occurs and homologous chromosomes pair up
  3. Crossing over between chromatids of homologous chromosome may occur
  4. The centrioles reach opposite poles of the cell
  5. Nuclear envelope and nucleolus disintegrates
  6. Spindle fibres form
35
Q

What is a pair of homologous chromosomes called?

A

bivalent

36
Q

What are the characteristics of homologous chromosomes?

A

Have the same shape, same genes and same length

One member of each pair is inherited from each parent

37
Q

How many chromosomes does one human cell have?

A

23 pairs (46 chromosomes)

38
Q

What is the point where homologous chromosomes cross over called?

A

chiasma

39
Q

What does crossing over between homologous chromosomes result in?

A

Results in new combination of genes along the chromosomes

40
Q

Overview of crossing over

A

Homologous chromosome → chromatids cross over with each other and exchange DNA → recombinant chromatids

41
Q

What happens during metaphase I?

A
  1. Homologous chromosomes arrange themselves along the equator
  2. One of each homologous pair faces the opposite pole
42
Q

What happens during anaphase I?

A
  1. Homologous chromosomes separate

2. One of each pair of the homologous chromosomes is pulled to the opposite pole of the cell

43
Q

What happens during telophase I? (animal cells)

A
  1. Spindle fibres disintegrate

2. Nuclear envelope reforms

44
Q

What happens during telophase I? (plant cells)

A

Most plant cells do not undergo Telophase I and move straight to Metaphase II

45
Q

What happens during cytokinesis I?

A
  1. The centrioles replicate

2. Cytoplasm cleaves to produce two daughter cells. The cells are now haploid.

46
Q

What happens during prophase II?

A
  1. Centrioles move to the opposite poles of the cell
  2. Nuclear envelope breaks down
  3. Spindle fibres appear
47
Q

What happens during metaphase II?

A
  1. The chromosomes line up singly along the equator
48
Q

How is metaphase II different from metaphase I?

A

The arrangement is different

  • Metaphase I: Chromosomes lie next to each other
  • Metaphase II: Chromosomes line up singly
49
Q

What happens during anaphase II?

A
  1. Centromeres divide and sister chromatids are separated

2. Daughter chromosomes are pulled to opposite poles of the cell

50
Q

What happens during telophase II?

A
  1. Spindle fibres disintegrate and nuclear envelopes form
51
Q

What happens during cytokinesis II?

A
  1. Cells divide, forming four daughter cells, each with a haploid number of chromosomes
52
Q

What is the importance of meiosis in sexual reproduction?

A 
Produces haploid (n) gametes, which fuse together during fertilisation to produce diploid (2n) cells
- Ensures that the number of chromosomes in an organism is maintained through successive generations
53
Q

Why is there a need for genetic variation in gametes?

A

This produces variations in the offspring, increasing the chances of survival of the species during changes in the environment

55
Q

How do genetic variations arise from meiosis?

A
  1. Random arrangement of homologous pairs of chromosomes at the equator at metaphase I
  2. Random separation of homologous chromosomes at anaphase I
  3. Different combinations of genetic materials in gametes
56
Q

Differences between mitosis and meiosis
Where does it occur?

A

Mitosis: Occurs in all cells
Meiosis: Occurs only in reproductive organs

57
Q

Differences between mitosis and meiosis
What is its function?

A

Mitosis: Growth of organism and repair of tissue
Meiosis: Produces gametes for sexual reproduction

58
Q

Differences between mitosis and meiosis

How many nuclear divisions does it involve?

A

Mitosis: Involves one nuclear division
Meiosis: Involves two nuclear divisions

59
Q

Differences between mitosis and meiosis

What does it produce?

A

Mitosis: 2 diploid daughter cells
Meiosis: 4 haploid daughter cells

60
Q

Differences between mitosis and meiosis

Compare the daughter cell and the parent cell

A

Mitosis: Daughter cells have the same number of chromosomes as parent cell. Daughter cells are genetically identical to parent cell and each other.
Meiosis: Daughter cells have half the number of chromosomes as parent cell. Genetic variation occurs in the daughter cells.

61
Q

Differences between mitosis and meiosis

Do homologous chromosomes pair up?

A

Mitosis: No
Meiosis: Yes, during prophase I

62
Q

Differences between mitosis and meiosis

Does crossing over occur?

A

Mitosis: No
Meiosis: Maybe

63
Q

At which points of meiosis do genetic variations arise?

A

Crossing over between homologous chromosomes at prophase I

Independent assortment of homologous chromosomes at metaphase I

IP Secondary 4 Biology (6 decks)

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