2.1.6 stages of meiosis

Question 1

what are homologous chromosomes

Answer 1

matching set of chromosomes
have same length, size, and have centromeres in same place
have same genes (alleles) on the same loci

Question 2

what is the difference between the two meiosis divisions

Answer 2

meiosis 1 = division of homologous chromosomes (reduction division)
meiosis 2 = division of chromatids

Question 3

explain what happens during prophase 1

Answer 3

chromosomes condense
nuclear envelope disintegrates
nucleolus disintegrates
spindle formation begins
homologous chromosomes pair up
as chromosomes move through cytoplasm chiasmata occurs

Question 4

describe how chiasmata occurs

Answer 4

adjacent chromatids cross over + twist around each other
pieces break off + rejoin other chromatids (exchange alleles)
produces recombinant chromosomes
this leads to GENETIC VARIATION

Question 5

explain what happens during metaphase 1

Answer 5

homologous chromosome pairs assemble at metaphase plate
organisation at plate is random
known as RANDOM ASSORTMENT

Question 6

describe the process of random assortment

Answer 6

the organisation of which chromosomes (maternal + paternal) go on which pole is random
forms a large variety of gamete combinations
leads to GENETIC VARIATION

Question 7

how can you calculate the number of gametes formed by random assortment

Answer 7

2^n
n = no. of chromosome pairs

Question 8

explain what happens during anaphase 1

Answer 8

spindle fibres contract
homologous chromosomes pulled apart
CHROMATIDS REMAIN JOINED TOGETHER

Question 9

explain what happens during telophase 1

Answer 9

nuclear membranes form around the chromosomes at each cell pole
chromosomes uncoil
cytokinesis occurs = cell divides into 2

Question 10

explain what happens during prophase 2

Answer 10

chromosomes condense + become visible
nuclear envelope breaks down again
spindle fibres reform

Question 11

explain what happens during metaphase 2

Answer 11

chromosomes assemble at metaphase plate
spindle fibres attach to centromeres of each chromosome

Question 12

explain what happens during anaphase 2

Answer 12

individual chromatids are separated
spindle fibres contract + pull chromatids in opposite direction

Question 13

explain what happens during telophase 2

Answer 13

chromatids end up at each cell pole
chromosomes uncoil
nuclear envelope reforms
nucleolus becomes visible
cytokinesis occurs = forms 4 daughter cells
= haploid cells
= all genetically different