meiosis Flashcards

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1
Q

what is the definition of heredity?

A

where traits are transmitted from one generation to the next

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2
Q

what is an example of asexual reproduction in multicellular organisms?

A

parthenogenesis in aphids

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3
Q

what are the advantages of asexual reproduction?

A

quick

works well in a non-changing environment

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4
Q

what are the disadvantages of asexual reproduction?

A

little to no variation

less ability to adapt to a changing environment

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5
Q

how many chromosomes do somatic human cells have>

A

46

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6
Q

what does meiosis do to the number of chromosomes in a cell?

A

reduces them from diploid to haploid

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7
Q

why is the reduction in the number of chromosomes in a cell during meiosis important?

A

without it chromosome sets would increase exponentially

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8
Q

what has to occur for homologous chromosomes to pair?

A

the chromosomes have to align

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9
Q

what do meiotic cells do?

A

they induce DNA breaks to find and hold homologous chromosomes together

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10
Q

what enzyme induces DNA breaks, in humans?

A

nuclease Spo11

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11
Q

how are DNA breaks repaired?

A

using a DNA repair mechanism that uses the matching information on the intact homologous chromosome - leading to a cross-over event

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12
Q

what causes a cross-over event?

A

repairs in the DNA breaks

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13
Q

what is a chaisma (chiasmata)?

A

what forms when DNA breaks are repaired and a crossing over event occurs

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14
Q

what do chiasmata ensure?

A

that homologous chromosomes stay together until mitotic division

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15
Q

what are homologous chromosomes?

A

chromosomes containing the same gene sequences - one is derived from each parent

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16
Q

how many parental chromosomes will each daughter cell have?

A

2

17
Q

how many crossed over chromosomes will the daughter cells have?

A

2

18
Q

what does the exchange of maternal and paternal chromosomes lead to?

A

an increase in recombinations and variation

19
Q

what happens during meiosis 1?

A

the homologous chromosomes seperate?

20
Q

what happens during meiosis 2?

A

the sister chromatids seperate

21
Q

what can happen when meiosis goes wrong?

A

sterility

alteration in chromosome number e.g. downs syndrome

22
Q

where does meiosis take place?

A

in the germline of adults

23
Q

what is the name of meiosis in males?

A

spermatogenesis

24
Q

what is name of meiosis in females?

A

oogenesis

25
Q

which stem cells do gametes arise from?

A

GSC’s germline stem cells

26
Q

what is an example of a GSC stem cell niche?

A

Male drosophilia flies have a niche called the hub. GSC’s touch the hub cells in the testis allowing the GSC’s to undergo multiple mitosis events and produce sperm

27
Q

what is an oocyte?

A

an immature egg cell

28
Q

what are the stages of meiosis in roundworms?

A
mitosis
transition 
beginning of meiosis 
arrest
fertilisation
completion of meiosis
29
Q

when does meiosis occur in oocytes?

A

after fertilisation

30
Q

what are polar bodies?

A

the remnants of discarded homologous chromosomes/sister chromatids