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Year 1 Medical Cell Biology And Genetics > Mitosis And Meiosis > Flashcards

Mitosis And Meiosis Flashcards

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1
Q

List stages of the cell cycle.

A 
Interphase- G0, G1, S and G2
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis
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2
Q

What is an allele?

A

Different variations of the same gene.

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3
Q

What do non-sister chromatids of homologous pairs have in common?

A

They carry the codes for the same genes, but the alleles may be different.

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4
Q

If the alleles are the same on two chromatids of a replicated chromatids they are called?

A

Sister chromatids.

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5
Q

What form are chromosomes in when drawn or seen in common Histological photos?

A

Replicated and condensed

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6
Q

What is a homologous pair?

A

Two copies of the same chromosome in each cell, one chromosome carrying paternal genetic information and the other carrying maternal information. The genes coded for may be the same but the alleles are different.

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7
Q

What stages of meiosis gives rise to genetic variation?

A

Random assortment of chromosomes in Metaphase 1 (line up paternal and maternal on different sided for each chromosome pair)
Crossing over in Prophase 1

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8
Q

What is G0?

A

G0 is the cell exiting the cell cycle either temporarily or permanently.
Nerve cells don’t replicate so they exist in G0
Liver cells temporarily enter this stage.

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9
Q

Do homologous pairs line up in mitosis?

A

No, that’s meiosis.
Mitosis all the chromosomes just line up randomly- no need for a partner because you want to just split the two chromatids from every chromosome- aim is identical cells.

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10
Q

What’s the nucleolus?

A

5 chromosomes coding the genes for rRNA in the herterochromatin.

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11
Q

How do homologous pairs find each other?

A

Sequences in each chromosome are similar at certain loci. It is this sequence recognition that lets them pair up.

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12
Q

What is a centromere?

A

The part of the chromosome that holds sister chromatids together. The centromere consists of a sequence of base repeats.

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13
Q

What is a telomere and why do we have them?

A

TTAGGG sequence repeats at the end of each chromatid to protect DNA from degradation. Replication shortens the telomere every time.

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14
Q

What is the p arm of an acrocentric chromosome called?

A

Satellite

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15
Q

The position of the centromere along with the size of the chromosome helps us identify and group them. Please name the 3 positions of centromere in humans.

A

Metacentric- middle
Submetacentric- just off the mid line
Acrocentric- way off centre, just a small piece on one side.

Telocentric at the telomeres doesn’t exist in humans

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16
Q

What is mitosis?

A

Cell division for somatic cells to produce 2 identical daughter cells that match the DNA of the parent cell exactly.

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17
Q

What kind of tissues require mitosis growth more regularly?

A

Cells that are frequently exposed to stress eg epidermal cells, mucosal cells
Cells that get used up to make things and would otherwise be used up in the process eg bone marrow and spermatagonia.

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18
Q

Describe mitosis prophase.

A

Nuclear membrane break down
Chromosomes condense
Spindles form

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19
Q

Describe mitosis Prometaphase

A

Spindle fibres attach to chromosomes

The chromosomes condense further

20
Q

Describe metaphase in Mitosis

A

Chromosomes line up on the midline- they are pulled by kinetochore so attached to the centrosomes at either pole of the cell.

21
Q

Describe Mitosis anaphase.

A

Sister chromatids separate and become individual unreplicated chromosomes.
The unreplicated chromosomes move to the poles, pulled by the kinetochores

22
Q

What happens in telophase of mitosis.

A

Nuclear membrane reforms
Spindles disappear
Chromosomes decondense

23
Q

What is cytokineses?

A

Cytoplasm division giving daughter cells

24
Q

How many chromosomes are in a cell?

A

23 homologous pairs so 46 individual chromosomes which may or may not be replicated depending on the stage of the cell cycle.

25
Q

In interphase the Chromosmes aren’t condensed so do the fall apart and separate?

A

They still exist in chromosomal territories, but they aren’t condensed like we normally visualise them.
We visualise replicated chromosomes in their homologous pairs.

26
Q

What is a replicated chromosome in its homologous pair called?

A

Bivalend or Tetrad

27
Q

What is meiosis?

A

Special cell division for germ line cells that produce non identical haploid cells from diploid parents. It involves one lot of DNA replication and two lots of cell division to make 4 haploid cells.

28
Q

Describe prophase in meiosis 1

A

Nuclear membrane degrades
Chromosome condense and find their homologous pair.
Crossing over.
Spindles form

29
Q

Describe Prometaphase in meiosis

A

Doesn’t exist

30
Q

Describe metaphase 1 in meiosis

A

The homologous pairs line up on the cell midline.

THIS IS THE ONLY TIME HOMOLOUS PAIRS LINE UP ANYWHERE IS ANY TIME OF CELL DIVISION.

31
Q

Which part of meiosis is responsible for haploid gametes?

A

Anaphase 1 where the HOMOLOGOUS pairs are separated not the sister chromatids. This results in 23 replicated chromosomes in each cell going into meiosis 2, not 46.

32
Q

Meiosis 2 is similar to mitosis- underline the key elements.

A

Prophase nuclear envelope breaks down and spindles form.
metaphase the 23 Chromosmes line up in the midline (note not 46 like in mitosis)
Anaphase splits up the sister chromatids to different poles of the cell.
Telophase reforms the nuclear envelope before cytokinesis.

33
Q

How many centrosomes should there be in any cell?

A

2, to make a bipolar cell in division- moves the sister chromatids to and end each.

34
Q

What is a key difference between meiosis 1 and meiosis 2

A

Meiosis 1 metaphase means 23 homloous pairs line up and anaphase means the pairs get split up into different cells.
Meiosis 2 metaphase lines up 23 chromosomes and anaphase separates sister chromatids

35
Q

Name 2 functions of meiosis

A

Conserve chromosome number from generation to generation.

Genetic diversity through random assortment in metaphase 1 and crossing over in prophase 1

36
Q

How long is spermatogenesis?

A

60days from spermatagonia to a mature sperm

37
Q

How long does oogenesis take and why is this a cause for concern in older mums?

A

12-50 years.

Meiosis only completes at fertilisation, that leaves chromosomes exposed for damage to their DNA for many years.

38
Q

What is misegregation of Chromosmes in meiosis?

A

When anaphase goes wrong, in either stage of meiosis. No dysjunction gives rise to Aneuploidy.

39
Q

What is mosaicism and what influences it?

A

More than one cell line in a organism or tissue.

The degree of mosaicism is influence by how far after the first zygotic division the change happens.

40
Q

What are mitosis spindles made from?

A

Micro tubules

41
Q

How do cancer treatments acting on the mitosis spindles help?

A

No spindles = no cell division= no tumour growth

42
Q

What is an oncogene?

A

Promoting cancer gene- we each have two one on each chromosome of the pair

43
Q

Where is Aneuploidy common?

A

Cancer

44
Q

How many tumour up pressing genes should you have?

A

2, one gene on each chromosome of the homlogous pair

45
Q

Mitosis errors in cancer can lead to:

A

Tumour heterogeneity
Numerical chromosome instability
Structural chromosomal instability

46
Q

What promotes numerical chromosomal instability?

A

More than two centrosomes in a cell- multipolar spindles

47
Q

How can we target centrosomes in cancer treatment?

A

It is common to have multiple centrosomes in cancer cell. These cells cluster at the two poles of the cell in mitosis which then results in viable cells. If the drug targets the clustering mechanism the daughter cells are likely to be less viable.
This is a cancer cell specific treatment- centrosomes don’t cluster in normal cells.

Year 1 Medical Cell Biology And Genetics (7 decks)

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