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IMMS Lectures > Mitosis and Meiosis > Flashcards

Mitosis and Meiosis Flashcards

1
Q

State main features of DNA and base pairing:

A
  • Double helix
  • Complimentary base pairs A - T (2 bonds), C - G (3 bonds)
  • Coils into nucleosomes (around histone proteins) > supercoils > chromosomes
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2
Q

How many pairs of chromosomes and what are they?

A

46 chromosomes, 22 autosome pairs, 1 pair sex chromosome XY - male & XX - female

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3
Q

Name the the three parts of a chromosome:

A

Long arm, q
Short arm, p
Separated by a centromere

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4
Q

What is a telomere and what does it do?

A

End section of chromosome.
Stop chromosome unravelling, shortens with each division, tolermerase rebuilds telomere.

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5
Q

What does mitosis produce and what is it used for ?

A
  • Produce 2 genetically identical daughter cells,
  • Growth, replace dead cells
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6
Q

Name the phases of mitosis:

A

Interphase - G1,S,G2
Prophase
Pro metaphase
Metaphase
Anaphase
Telophase
Cytokinesis

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7
Q

What happens in Interphase: G1

A

G1: no visible activity but the following occurs
- Rapid growth
- Normal metabolic function
- New organelles produced
- Protein synthesis of proteins involved in spindle formation

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8
Q

What happens in Interphase: S phase

A
  • DNA x2 through DNA replication
  • Histone proteins x2 through protein synthesis ( 2 x as much DNA at end of S)
  • Centrosome replication
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9
Q

What happens in Interphase: G2

A

G2 - 4n chromosomes (normally 2n)
- Chromosomes condense (coil up and become visible)
- Energy stores accumulate
- Mitochondria and centrioles doubles

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10
Q

What happens in prophase:

A
  • Chromatin condenses into chromosomes
  • Centrosomes nucleate microtubules and move to opposite poles of nucleus
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11
Q

What happens in pro metaphase:

A
  • Nuclear membrane breaks down
  • Microtubules invade nuclear space
  • Chromatids attach to microtubules
  • Cell no longer has a nucleus
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12
Q

What happens in metaphase:

A

Chromosomes line up along equatorial plane (metaphase plate)

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13
Q

What happens in anaphase:

A
  • Microtubules shorten
  • Sister chromatids separate, and are pushed to opposite poles of the cells, centromere first, as spindle fibres contract
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14
Q

What happens in telophase:

A
  • Nuclear membrane reforms around 2 nuclei
  • Chromosomes unfold into chromatin
  • Cytokinesis begins
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15
Q

What happens in cytokinesis:

A
  • Cell organelle become evenly distributed around each nucleus
  • Cell divides into two daughter cells with a nucleus in each and 46 chromosomes
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16
Q

Clinical relevance of mitosis:

A
  • Detect chromosomal abnormalities eg downs syndrome
  • Categorise tumours as - benign or malignant
  • In histology - mitotic cells dark nucleus
  • Grading malignant tumours - too many mitotic figure i.e. lots of dark nuclei of different sizes
  • No. of mitotic figures determine how bad cancer is, the more there are, the worse it is
  • Anti mitosis drug - taxol (mitotic spindle), ispinesib (spindle poles) and colchicine like drugs (anaphase) can help treat cancer?
17
Q

First stage of gametogenesis:

A

The first stage is the proliferation of primordial (undifferentiated) germ cells by mitosis

18
Q

When does mitosis occur in male gametogenesis?

A

Some mitosis occurs in embryonic stages to produce primary spermatocytes present at birth
Mitosis begins during puberty, continues throughout life

19
Q

How many gametes are produced in male gg and how long does it take?

A
  • Cytoplasm divides evenly
  • After meiosis 2 - four equal size gametes
  • Takes 60-65 days
20
Q

How many mitoses occur in female gametogenesis?

A

30

21
Q

When does oogonia enter meiosis?

A
  • Oogonia enter prophase 1 of meiosis 1 by 8th month of intrauterine life (in-utero)
  • Process suspended
  • Meiosis 1 is completed at ovulation 10-50 yrs later (then cells remain in suspended animation) - at this point there is 1 big cell, 1 small cell each with diploid DNA. Then go on to divide again each, after fertilisation
  • Meiosis 2 is only completed if fertilisation occurs
22
Q

What is produced after female gg:

A

Cytoplasm divides unequally - 1 egg & 3 polar bodies (that apoptose after meiosis 2)

23
Q

Issues with meiosis:

A
  • Non disjunction - Chromosomes don’t separate after M1 or sister chromatids in M2
  • Downs syndrome - Non-disjunction at chromosome 21 resulting in trisomy 21
  • Monosomy (loss of chromosome) - Turners syndrome, only 1 X chromosome.
24
Q

What is Gonadal mosaicism:

A

Precursor germline cells to ova or spermatozoa are a mixture of two or more genetically different cell lines (due to errors in mitosis - random mutation)

IMMS Lectures (16 decks)

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