meiosis

Question 1

stages of prophase 1

Answer 1

1) leptotene
2) zygotene
3) pachytene
4) diplotene
5) diakinesis

Question 2

leptotene

Answer 2

chromatin condensed to form chromosomes which are not yet split into sister chromatids. chromomeres are visible along their line

Question 3

zygotene

Answer 3

homologous chromosomes (maternal-paternal) pair together to form bivalents. chromosomes now split into sister chromatids and local sites of alignment [synapsis] develop between sister chromatids of homologous pairs

Question 4

pachytene

Answer 4

synapsis is completed and ‘crossing over’ [chiasmata formation] occurs

Question 5

diplotene

Answer 5

chromatids are held together by chiasmata as well as by the centromeres

Question 6

diakinesis

Answer 6

chiasmata appear to begin to move along the chromatids [terminilisation]

Question 7

metaphase 1

Answer 7

each bivalent has 2 centromeres which by chance arrange themselves on opposite sides of the metaphase plate. independent assortment occurs.

Question 8

anaphase 1

Answer 8

chromosomes move to opposite sides of the cell

Question 9

telophase 1

Answer 9

each daughter has half the number of chromosomes. the nuclear envelope may reassemble before prophase 2 of the second meiotic division

Question 10

meiosis 2

Answer 10

these are morphologically similar to those seen in mitosis. centromeres not split at kinetochores and sister chromatids move to opposite poles . at the end of the 2 divisions, potentially 4 gametes are formed

Question 11

numerical chromosome abnormality

Answer 11

too few or too many chromosomes

Question 12

structural chromosome abnormality

Answer 12

the chromosome structure has been altered