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𝔹𝕚𝕠𝕝𝕠𝕘𝕪 F4 > Chapter 6: Cell Division till (6.3) > Flashcards

Chapter 6: Cell Division till (6.3) Flashcards

1
Q

What is meiosis?

A
  • a process of nuclear division that reduces the chromosome number in daughter cells by half
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2
Q

What is the necessity of meiosis?

A
  • formation of gametes
  • producing genetic variation
  • maintaining diploid chromosomal numbers
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3
Q

Meiosis involves two ____ divisions, that is _______ and _____.

A
  • nuclear
  • meiosis I
  • meiosis II
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4
Q

Explain prophase I.

A
  • centrioles move to opposite poles
  • chromosomes condense and become visible
  • homologous chromosomes pair up and form bivalent or tetrad through synapsis
  • crossing over between non-identical chromatids occur in chiasmata
  • nuclear membrane disintegrates and the nucleolus disappears
  • spindle fibers are formed
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5
Q

Explain metaphase I

A
  • paired homologous chromosomes line up along the equator

- centromere is attached to the spindle fibers

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6
Q

What happens at anaphase I?

A
  • spindle fibers pull the homologous chromosomes apart from each other
  • each pair still consists of a pair of sister chromatids
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7
Q

What occurs at telophase I.

A
  • each set of chromosomes containing haploid chromosomes arrive at opposite poles
  • spindle fibers disappear
  • nuclear membrane reforms
  • chromosomes uncoil
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8
Q

Explain prophase II and metaphase II.

A 
Prophase II
- nuclear membrane breaks down again
- spindle fibers begin to form
Metaphase II
- chromosomes line up along the equator
- spindle fibers attach to the chromosomes
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9
Q

What occurs in anaphase II and telophase II.

A

Anaphase II
- spindle fibers contract
- sister chromatids separate and move to opposite poles
- each sister chromatid is known as chromosome
Telophase II
- chromosomes uncoil to become chromatin
- spindle fibers disappear
- new nuclear membrane forms around each group of chromosomes

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10
Q

Explain cytokinesis.

A
  • four haploid daughter cells are formed

- content of each daughter cell is genetically different from the parent cell

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11
Q

What are the similarities between mitosis and meiosis?

A
  • both involve nuclear and cytoplasmic division
  • DNA replicated only once
  • involve movement chromosomes
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12
Q

What are the differences between mitosis and meiosis?

A

Mitosis

  • occur in somatic cells
  • one nuclear division
  • synapsis does not occur
  • no crossing over
  • two daughter cells produced
  • diploid chromosome number
  • daughter cells are genetically identical to the parent cell

Meiosis

  • occur in reproductive organs
  • involve two nuclear division
  • synapsis occur in Prophase I
  • crossing over occurs
  • four daughter cells produced
  • haploid chromosome number
  • daughter cells are not genetically identical to the parent cell
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13
Q

What are the similarities between meiosis I and meiosis II?

A
  • involve nuclear and cytoplasmic division

- consist of four stages

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14
Q

What are the differences between meiosis I and meiosis II?

A

Meiosis I

  • synapsis occur
  • crossing over occur
  • reduces from diploid to haploid
  • during metaphase I, paired homologous chromosomes line up at the equator

Meiosis II

  • synapsis does not occur
  • crossing over does not occur
  • maintains the haploid number
  • during metaphase I, chromosomes line up at the equator
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15
Q

Cell division can be disrupted by substances such as ______ and _______ _______.

A
  • radiation

- carcinogenic substances

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16
Q

If abnormal mitosis occurs, the cell divides ___ __ ______ which is called _______ _______.

A
  • out of control

- uncontrolled mitosis

17
Q

The cell divides rapidly and non-stop, producing a mass of abnormal cells that form a ______.

A
  • tumor.
18
Q

Describe the two types of tumors.

A

Benign tumor- abnormal cells remain at the original site

Malignant tumor- invade and spread to other tissues in the body impairing their functions

19
Q

Describe the process of tumor growth.

A
  • normally dividing cells are subjected to prolonged exposure to carcinogen
  • carcinogen causes mutation
  • mutated cell undergoes repeated and rapid mitosis
  • a malignant tumor competes with surrounding cells to obtain nutrients
  • a benign tumor absorbs nutrients, enlarges but does not spread from the original site
20
Q

What are the effects of abnormal meiosis on human health?

A
  • non-disjunction occurs where the gametes formed will have an abnormal number of chromosomes ( due to spindle malfunction in spindle fibres )
  • hence the zygote would be abnormal causing down syndrome

𝔹𝕚𝕠𝕝𝕠𝕘𝕪 F4 (10 decks)

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