meiosis

Question 1

what is the definition of heredity?

Answer 1

where traits are transmitted from one generation to the next

Question 2

what is an example of asexual reproduction in multicellular organisms?

Answer 2

parthenogenesis in aphids

Question 3

what are the advantages of asexual reproduction?

Answer 3

quick

works well in a non-changing environment

Question 4

what are the disadvantages of asexual reproduction?

Answer 4

little to no variation

less ability to adapt to a changing environment

Question 5

how many chromosomes do somatic human cells have>

Answer 5

46

Question 6

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

Answer 6

reduces them from diploid to haploid

Question 7

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

Answer 7

without it chromosome sets would increase exponentially

Question 8

what has to occur for homologous chromosomes to pair?

Answer 8

the chromosomes have to align

Question 9

what do meiotic cells do?

Answer 9

they induce DNA breaks to find and hold homologous chromosomes together

Question 10

what enzyme induces DNA breaks, in humans?

Answer 10

nuclease Spo11

Question 11

how are DNA breaks repaired?

Answer 11

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

Question 12

what causes a cross-over event?

Answer 12

repairs in the DNA breaks

Question 13

what is a chaisma (chiasmata)?

Answer 13

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

Question 14

what do chiasmata ensure?

Answer 14

that homologous chromosomes stay together until mitotic division

Question 15

what are homologous chromosomes?

Answer 15

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

Question 16

how many parental chromosomes will each daughter cell have?

Answer 16

2

Question 17

how many crossed over chromosomes will the daughter cells have?

Answer 17

2

Question 18

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

Answer 18

an increase in recombinations and variation

Question 19

what happens during meiosis 1?

Answer 19

the homologous chromosomes seperate?

Question 20

what happens during meiosis 2?

Answer 20

the sister chromatids seperate

Question 21

what can happen when meiosis goes wrong?

Answer 21

sterility

alteration in chromosome number e.g. downs syndrome

Question 22

where does meiosis take place?

Answer 22

in the germline of adults

Question 23

what is the name of meiosis in males?

Answer 23

spermatogenesis

Question 24

what is name of meiosis in females?

Answer 24

oogenesis

Question 25

which stem cells do gametes arise from?

Answer 25

GSC's germline stem cells

Question 26

what is an example of a GSC stem cell niche?

Answer 26

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

Question 27

what is an oocyte?

Answer 27

an immature egg cell

Question 28

what are the stages of meiosis in roundworms?

Answer 28

``` mitosis transition beginning of meiosis arrest fertilisation completion of meiosis ```

Question 29

when does meiosis occur in oocytes?

Answer 29

after fertilisation

Question 30

what are polar bodies?

Answer 30

the remnants of discarded homologous chromosomes/sister chromatids