L13- Meiosis Flashcards

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1
Q

meiosis is

A

division for germ line cells

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2
Q

production of sperm

A

spermatogenesis

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3
Q

production of eggs

A

oogenesis

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4
Q

meiosis creates

A

haploid cells- sperm and eggs

2n–> n

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5
Q

sperm and eggs will

A

two haploid cells will join at fertilisation and form a couple diploid set- new genome

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6
Q

meiosis produces ……. cells

A

non-identical

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7
Q

meiosis is one round of replication followed by

A

two rounds of division to separate sister chromatids

  • meiosis 1
  • meiosis 2
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8
Q

order of meiosis 1

A

prophase 1
metaphase 1
anaphase 1
telophase 1

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9
Q

prophase 1

A

somes begins to condense and pair up(homologous chromosomes (from mums and dad) will look for each other)

  • Each chromosome carefully aligns with homologues partner so that two match up at corresponding positions along their full length
  • Homologues recombination occurs via crossing over.
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10
Q

homologous recombination occurs via crossing over

A

o DNA is broken at the same spot on each homologue and exchange part of their DNA
o Crossing over occurs as chiasmata- cross shaped structures where homologues are linked together
o Chiasmata keep homologues connected
o Can have multiple cross overs

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11
Q

metaphase 1

A

spindle begins to capture chromosomes and move them towards the centre of the cell- metaphase plate

  • Each chromosome attaches to microtubule from just one pole of the spindle
  • Homologous pairs not individual chromosomes line up for separation.
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12
Q

when homologous pairs line up at the metaphase plate

A

the orientation of each pair is random

- gametes will have diff set of homologues

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13
Q

anaphase 1

A

homologues are pulled apart and move apart to opposite ends of the cell
- Sister chromatids of each chromosome remain attached to one another and
don’t come apart

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14
Q

telophase 1

A

chromosomes arrive at opposite poles of the cell

  • Cytokinesis occurs at the same time as telophase I
  • Cleavage- formation of two haploid non-identical daughter cells
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15
Q

cells move from meiosis II to II without

A

copying their DNA

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16
Q

how is meiosis II diff to meiosis I

A

shorter and simpler

- basically mitosis for haploid cells

17
Q

cells that enter meiosis II

A

are haploid and have one chromosome from each homologues pair

but chromosomes still consist of two sister chromatids

18
Q

prophase II

A

Chromosome condense and nuclear envelop breaks down- if needed

  • Centrosomes move apart
  • Spindle forms between them
  • Two sister chromatids are captures by microtubules from opposite spindle poles
19
Q

metaphase II

A

the chromosomes line up individually along the metaphase plate.

20
Q

anaphase II

A

sister chromatids separates and are pulled towards opposite poles of the cell

21
Q

telophase II

A

nuclear envelopes form around each set of chromosomes and the chromosomes decondense.
- Cytokinesis splits the chromosome set into new cells

22
Q

at the end of telophase II you have

A

4 haploid cells in which each chromosomes has just one chromatid

23
Q

consequence of meiosis

A
  • Maintaining constant chromosomes number from generation to generation
  • Generation of genetic diversity
24
Q

how does meiosis produce genetic diversity

A

o Random assortment of chromosomes on the metaplate

o Crossing over of genetic material

25
Q

spermatogenesis

A

cell vision to produce male gametes (sperm)

26
Q

outline spermatogenesis

A

1) spermtogonium (2n) becomes a primary spermatocyte (2n)
2) spermatocyte undergoes meiosis –> 4 spermatids (n)
3) spermatids mature to sperm

1 spermacyte (2n) –> 4 sperm (n)

27
Q

how long does spermatogenesis take

A

60 days

28
Q

outline oogenesis

A

1) oogonium (2n) mature to become a primary oocyte (2n)

2) meiosis of primary oocyte (2n) forms 4 haploid cells

29
Q

describe the 4 haploid cells produced in oogenesis

A

1 mature ovum

3 polar bodies

30
Q

length of oogenesis

A

12-50 years