Meiosis

Question 1

what are homologous chromosomes

Answer 1

• set where one is maternal, one is paternal

Question 2

process of meiosis

Answer 2

meiosis I = reduction division
- prophase 1
-metaphase 1
- anaphase 1
- telophase 1 and cytokinesis
meiosis II = equational division
- pro, met, ana, telo, cytokinesis

Question 3

meiosis I - prophase 1

Answer 3

• homologous chromosomes pair up
• crossing over - synaptomal complex disappears and leaves chiasma
• nuclear envelope fragments
• ## join at synaptomal complex

Question 4

meiosis 1 - metaphase 1

Answer 4

• pairs line up at spindle equator

Question 5

meiosis 1 - anaphase 1

Answer 5

• sister chromatids of each chromosome move together towards spindle poles - the homologous pairs move apart

Question 6

meisosis 1 - telophase and cytokinesis

Answer 6

• telophase: chromosomes reach spindle pole, nuclear envelop reforms
• cytokinesis: generates two haploid cells (two diploid cells)

Question 7

meiosis II result

Answer 7

4 haploid duaghter cells
- divides each of two cells so that they only have

Question 8

how is genetic information exchanged and randomised in gametes

Answer 8

1. crossing over - homologous chromosomes will exchange information
2. indpendent assortment - chromosomes (sister chromatids separated) randomly distributed into daughter cells

Question 9

how many times does DNA rep occur in meisois

Answer 9

once during interphase!!!

Question 10

how do sperm cells form

Answer 10

• diploid spermatocyte
• division into 4 haploid spermatids that become sperm

Question 11

how does egg form

Answer 11

• 1 diploid oocyte divides into three haploid polar bodies and 1 egg cell
• 3 polar bodies disintigrate into 1 big haploid egg cell

Question 12

how do defects occur in meiosis

Answer 12

1. nondsjunction e.g. down syndrome
2. defects in chromosome structure - muations e.g. cancer