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1 IMMS > mitosis and meiosis > Flashcards

mitosis and meiosis Flashcards

1
Q

name the complementary base pairs in DNA?

A
  • guanine to cytosine (3 x H bonds)

- adenine to thymine (2 x H bonds)

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2
Q

how many chromosomes in the human genome?

A
  • 46 chromosomes
  • 23 pairs

( 22 pairs of autosomes + 1 pair of sex chromosomes )

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3
Q

describe the structure of a chromosome

A
  • linear
  • long q arm, short p arm
  • arms separated by the centromere
  • telemores at ends
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4
Q

what is a telomeric DNA?

A
  • non coding DNA on end of a chromosome
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5
Q

what role does telomeric DNA play in ageing?

A
  • gets shorter with each cell replication

- once a chromosome has run out of telomeric DNA it won’t replicate again

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6
Q

how much genetic material does each chromes contain?

A

~10^7 base pairs of genetic material

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7
Q

what is the purpose of mitosis?

A

to produce 2 identical daughter cells each with 23 pairs of chromosomes (diploid cells)

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8
Q

what are the stages of the cell cycle?

A 
G1 - growth phase 
S - synthesis phase
G2 - growth phase 
mitosis
(+ cytokinesis)
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9
Q

what happens during the G1 phase of the cell cycle?

A
  • cell replicates
  • produces more organelles in cytoplasm
  • enlarges
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10
Q

what happens during the S phase of the cell cycle?

A
  • DNA replication
  • centrosome replication
  • ATP content increases
  • if errors found, repairs or apoptosis
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11
Q

what happens during the G2 phase of the cell cycle?

A
  • short growth phase

- prep for mitosis

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12
Q

what are the 5 stages of mitosis?

A
  1. prophase
  2. prometaphase
  3. metaphase
  4. anaphase
  5. telophase
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13
Q

what happens in the prophase stage of mitosis?

A
  • chromatin condenses in to chromosomes
  • centrosomes nucleate microtubules and move to opposite poles of the nucleus

*nucleus still has a membrane and contains the chromosomes

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14
Q

what happens in the prometaphase stage of mitosis?

A
  1. nuclear membrane breaks down
  2. microtubules invade the nuclear space
  3. chromatids (in pairs) attach to microtubules
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15
Q

what happens in the metaphase stage of mitosis?

A
  1. chromosomes line up along the equatorial plane ie. the metaphase plate
  2. the band of chromosomes are attached to the microtubules
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16
Q

what happens in the anaphase stage of mitosis?

A
  1. the replicated sister chromatids are separated
  2. they are pulled to opposite poles of the cell
  3. this happens because the microtubules shorten, and this pulls one of each away
  4. chromatids appear v shaped
17
Q

what happens in the telophase stage of mitosis?

A
  • nuclear membranes form around the opposite poles
  • chromosomes unfold into chromatin
  • cytokinesis begins ( cell division) and 2 identical daughter cells form
18
Q

what is G0 in the cell cycle?

A
  • some cells don’t divide, they are stable and permanent
  • these stay outside of the cycle, in the “G0” phase
  • these cells won’t undergo mitosis
19
Q

which steps in the cell cycle make up the interphase?

A

G1,S,G2

everything but mitosis and G0

20
Q

how can mitotic activity indicate cancerous epithelium?

A

it is abnormal when lots of epithelial cells going through different stages of mitosis at different levels of the epithelium

21
Q

which is the easies stage of mitosis to see histologically?

A

metaphase

22
Q

in what cells does meiosis occur?

A

gametes

23
Q

what are haploids and what are diploid cells?

A

diploid = 46 chromosomes (23 pairs)

haploid = 23 chromosomes

24
Q

how many cell divisions occur in meiosis?

A

2 cell divisions

meiosis 1
meiosis 2

25
Q

what are the end products of meiosis?

A

4 non-identical haploid daughter gametes

26
Q

what is the key step in meiosis?

A

prophase 1 - Cross over

because the homologous chromosomes exchange small parts of themselves, which results in mixing of paternal and maternal DNA

27
Q

what are the chiasmata?

A

the points on aa chromosome where cross over has occurred

28
Q

what is non-disjunction?

A

failure of chromosome pairs to separate in meiosis I or sister chromatids to sepreate properly in meiosis II

results in an abnormal number of chromosomes in the daughter cells

29
Q

which chromosome abnormality causes down syndrome ?

A

non- disjunction in 21st chromosome,
3 copies instead of 2
trisomy 21

30
Q

what is gonadal mosaicism?

A

where more than one set of genetic information is found within the gamete cells

as a result of a mutation in some of the germ cells

no longer 4 identical haploids

31
Q

which conditions is gonadal mosaicism most commonly seen in?

A

autosomal dominant and X-linked conditions

1 IMMS (4 decks)

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