3. Mitosis & Meiosis Flashcards Preview

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Flashcards in 3. Mitosis & Meiosis Deck (30)
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1
Q

What type of cells undergo mitotic cell division?

A

Somatic cells

2
Q

What is the product of mitosis?

A

2 identical daughter cells with exactly the same chromosomal content as the parent cell. Diploid cells with 23 pairs of chromosomes.

3
Q

Just before meiosis, what does the DNA look like in G2?

A

Chromosomes are replicated and sister chromatids are joined by a centromere. Not visible at this point as not condensed.

4
Q

What are the 5 stages of mitosis?

A

Prophase, Prometaphase, Metaphase, Anaphase & Telophase

5
Q

What happens in prophase which makes the DNA visible?

A

chromosomes condense

6
Q

At what stage do the spindle fibres attach to the centromeres?

A

Prometaphase

7
Q

What happens in metaphase?

A

The chromosomes line up along the metaphase plate

8
Q

In what phase does the nuclear envelope reappear in mitosis?

A

Telophase

9
Q

What differs during anaphase in mitosis and meiosis I?

A

In mitosis, the chromosomes are pulled apart and each chromatid is pulled to a different side of the cell.
During meiosis I, homologous chromosomes are separated. These are then separated into chromatids during meiosis II.

10
Q

What are telomeres and where are they located?

A

They are repeated sequences of DNA which are at each end of chromosome/chromatid. They protect DNA from degradation.

11
Q

What are the names for different position of the centromere, starting from central and working upwards.

A

Metacentric (central), submetacentric, acrocentric and telocentric (not in humans)

12
Q

During meiosis, when does crossing over/recombination occur?

A

Prophase I

13
Q

What is a bivalent or tetrad and when can it be seen?

A

It is when 2 replicated chromosomes, homologous pairs line up on the metaphase plate during metaphase I of meiosis.

14
Q

What are the 2 processes which lead to genetic variation in meiosis?

A
  1. Random assortment of homologous pairs on metaphase plate.

2. Crossing over and exchanging of genetic information

15
Q

What is the product of meiosis?

A

4 non identical haploid (n) daughter cells

16
Q

How many chromosomes do the dividing cells have at the end of meiosis I?

A

Haploid (n) = 23 chromosomes

17
Q

How many chromosomes do the haploid daughter cells have after meiosis?

A

23 chromosomes (not paired)

18
Q

What is the difference in cell division in spermatogenesis and oogenesis?

A

Spermatogenesis produces 4 sperm (n) from 1 spermatocyte (2n) whereas oogenesis produces 1 egg (n) and 3 polar bodies from 1 oocyte (2n)

19
Q

What is a common cause of aneuploidy?

A

Non-disjunction of chromosomes during metaphase

20
Q

What will the be the result of non-disjunction at the first post-zygotes mitotic division?

A

46,N will divide to produce one monosomy cell line and one trisomy cell line. The monosomy cell line is usually lost.

21
Q

What is the result of non disjunction at later mitotic cell divisions?

A

46N will produce one monosomy cell line and one trisomy cell line. The monosomy will be lost and the trisomy will be combined with the normal cells. MOSAIC karyotype.

22
Q

What is mosaicism?

A

The presence of 2 or more cell lines in an individual

23
Q

What determines the degree of mosaicism?

A

When the non-disjunction takes place, later mitotic divisions will affect fewer cells.

24
Q

What will be the effect of non-disjunction in meiosis 1 ?

A

All offspring will have the wrong chromosome number. Half will be monosomy and half will be trisomy when fertilised.

25
Q

What happens if there is non-disjunction in meiosis II?

A

Half of the offspring will have the wrong chromosome number ( one trisomy and one monosomy) and have will be normal.

26
Q

What is a robertsonian translocation?

A

When 2 acrocentric chromosomes q arms fuse and p arms are lost, so the indictable will have 45 chromosomes.

27
Q

What gene is responsible for the initiation of male sex?

A

SRY gene on the Y chromosome

28
Q

23 unduplicated structures are seen to travel to each pole, what cell division is this?

A

Meiosis II.
Duplicated in meiosis I
46 in mitosis

29
Q

During mitosis, when does the Nucleolus disappear?

A

During prophase when the chromosomes are condensed and will only return when chromosomes decondense.

30
Q

What are the consequences of faulty meiosis ?

A
  • infertility
  • mental retardation
  • miscarriage