L13- Meiosis

Question 1

meiosis is

Answer 1

division for germ line cells

Question 2

production of sperm

Answer 2

spermatogenesis

Question 3

production of eggs

Answer 3

oogenesis

Question 4

meiosis creates

Answer 4

haploid cells- sperm and eggs

2n–> n

Question 5

sperm and eggs will

Answer 5

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

Question 6

meiosis produces ……. cells

Answer 6

non-identical

Question 7

meiosis is one round of replication followed by

Answer 7

two rounds of division to separate sister chromatids

• meiosis 1
• meiosis 2

Question 8

order of meiosis 1

Answer 8

prophase 1
metaphase 1
anaphase 1
telophase 1

Question 9

prophase 1

Answer 9

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.

Question 10

homologous recombination occurs via crossing over

Answer 10

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

Question 11

metaphase 1

Answer 11

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.

Question 12

when homologous pairs line up at the metaphase plate

Answer 12

the orientation of each pair is random

- gametes will have diff set of homologues

Question 13

anaphase 1

Answer 13

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

Question 14

telophase 1

Answer 14

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

Question 15

cells move from meiosis II to II without

Answer 15

copying their DNA

Question 16

how is meiosis II diff to meiosis I

Answer 16

shorter and simpler

- basically mitosis for haploid cells

Question 17

cells that enter meiosis II

Answer 17

are haploid and have one chromosome from each homologues pair

but chromosomes still consist of two sister chromatids

Question 18

prophase II

Answer 18

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

Question 19

metaphase II

Answer 19

the chromosomes line up individually along the metaphase plate.

Question 20

anaphase II

Answer 20

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

Question 21

telophase II

Answer 21

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

Question 22

at the end of telophase II you have

Answer 22

4 haploid cells in which each chromosomes has just one chromatid

Question 23

consequence of meiosis

Answer 23

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

Question 24

how does meiosis produce genetic diversity

Answer 24

o Random assortment of chromosomes on the metaplate

o Crossing over of genetic material

Question 25

spermatogenesis

Answer 25

cell vision to produce male gametes (sperm)

Question 26

outline spermatogenesis

Answer 26

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)

Question 27

how long does spermatogenesis take

Answer 27

60 days

Question 28

outline oogenesis

Answer 28

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

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

Question 29

describe the 4 haploid cells produced in oogenesis

Answer 29

1 mature ovum

3 polar bodies

Question 30

length of oogenesis

Answer 30

12-50 years