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Biology 2020 > Mitosis And Meiosis > Flashcards

Mitosis And Meiosis Flashcards

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1
Q

Definition of mitosis

A

a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.

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2
Q

Definition of meiosis

A

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell.

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3
Q

What are the stages of mitosis?

A

Prophase, metaphase,anaphase and telophase

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4
Q

What happens during prophase?(mitosis)

A
  1. Chromatin threads condense, coil and shorten to become chromosomes.
    2.Each chromosomes consists of 2 sister chromatids attached at the centromere(visible under the microscope)
    Animal cell:
  2. Asters(made up of microtubules) from around the centrioles.
  3. The centrioles move apart to the opposite poles of the cell.
  4. The nucleolus and the nuclear envelope disappear
  5. Spindle fibers form, extending from one pole of the cell to the other.
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5
Q

What happens during metaphase?(mitosis)

A
  1. Chromosomes line up along the equatorial plane of the spindle
  2. The centromere of each chromosomes is attached to a spindle fiber on each respective sides.
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6
Q

What happens during the anaphase?(mitosis)

A
  1. Each centromere divides.
  2. The spindle fibres shorten and and pull the chromatids apart to the opposite poles of the cell.
  3. Once the chromatids are separated, they are called daughter chromosomes
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7
Q

What happens during cytokines?(mitosis)

A

Division of cytoplasm.
Animal cell:
1. Furrows appear in the cytoplasm between the 2 nuclei
2. The furrows deepen and 2 identical daughter cells are separated.

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8
Q

What happens during Telophase?(mitosis)

A
  1. Spindle fibres break down
  2. A nuclear envelope forms around the chromosomes at each pole of the cell.
  3. A nucleolus reforms in each nucleus.
  4. Chromosomes uncoil and lengthen to become thin chromatin threads.
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9
Q

What is the difference between mitosis in animal cell and mitosis in plant cell?

A
  1. Centrioles are absent in a plant cell

2. Furrows do not form during cytokinesis. A cell plate is formed between 2 daughter nuclei , dividing the cell into two

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10
Q

How does the cell plate form?

A

It is formed by the fusion of small fluid-filled vesicles produced by the Golgi apparatus

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11
Q

Why is mitosis important?

A
  1. Mitosis enables the growth of an organism
  2. Mitosis is needed for the repair if worn-out parts of the body
  3. Mitosis allows asexual reproduction to occur
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12
Q

What are gametes?

A

Gametes are reproductive cells that contain half the number of chromosomes as the normal body cells.

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13
Q

Why are gametes produced?

A

Sexual reproduction involves the fusion of 2 gametes during fertilization.

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14
Q

What is meiosis?

A

Meiosis is a form of nuclear division that produces daughter nuclei containing half of the number of chromosomes as the parent nucleus.

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15
Q

What happens during interphase?

A

1.Chromatin threads replicate, producing 2 identical sister chromatids connected together at the centromere.

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16
Q

What happens during prophase I? ( meiosis I)

A
  1. Chromatin threads condense, coil and shorten to become chromosomes. Each chromosome consists of 2 sister chromatids connected together at the centromere ( visible under the microscope)
  2. One Homologous chromosomes from the female and the other from the male pair up.
  3. Chromatids of the homologous chromosomes may cross and twist around one another. The point where they cross one another is the chiasma.
  4. The chromosomes may break and exchange parts(crossing over)
  5. Centrioles move away from each other to opposite poles of the cell
  6. Aster form around the centrioles that are situated at the opposite poles of the cell
  7. The nuclear envelope and the nucleolus disappear
  8. Spindle fibres form.
17
Q

What happens during metaphase I ( meiosis I)?

A
  1. Pairs of homologous chromosomes arrange themselves along the equatorial plane of the spindle.
  2. Each chromosomes is attached to a single fibre.
18
Q

What happens during anaphase I (meiosis I)?

A

1.Homologous chromosomes separate and are pulled to opposite poles of the cell as the spindle fibres shorten.

19
Q

What happens during telophase I (meiosis I)?

A
  1. A nuclear envelope forms around the chromosomes at each pole.
20
Q

What happens during cytokinesis I ?(meiosis l)

A
  1. The cytoplasm cleaves into 2 (2 daughter cells, each with haploid number of chromosomes)
  2. The centrioles divide again
21
Q

Prophase II (meiosis II)

A
  1. The two pairs of centrioles move to opposite poles of the cell.
  2. Nuclear envelope disappears.
  3. Spindle fibres appear.
22
Q

Metaphase II (meiosis II)

A
  1. Chromosomes arrange themselves along the equatorial plane of the spindle
23
Q

Anaphase II (meiosis II)

A
  1. Centromeres divide

2. Sister chromatids separate to form daughter chromosomes, which are pulled towards the opposite poles of the cell.

24
Q

Telophase II (meiosis II)

A
  1. Spindle fibres disappear.
  2. Nuclear envelopes form around the 2 daughter chromosomes at each pole
  3. A nucleolus reforms
25
Q

Cytokinesis II (meiosis II)

A
  1. Cleavage of cytoplasm separates the the cytoplasm between the 2 nucleolus in each cell. 4 daughter cells are produced. (Each with half the number of chromosomes as the parent cell)
26
Q

The need for genetically identical cells

A

If an error occurs during DNA replication(mitosis) , it will be transmitted to the daughter cells—> may lead to harmful changes to the genes and affect the functions of daughter cells. Eg. Mistakes in mitosis may result in uncontrolled cell division—> cancer can be fatal as the cells lose the ability to control their division and they are unable to perform their normal functions.

27
Q

What is a pair of homologous chromosomes?

A

Homologous chromosomes have the same shape , same

28
Q

The need for a reduction in chromosomes in meiosis

A

When the haploid gamete from the male fuses with the haploid gamete from the female, the diploid number of chromosomes is restored in the zygote.

Biology 2020 (13 decks)

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