Meiosis

Question 1

Crossing over

Answer 1

• chromatids from 1 chromosome twists around a chromatid from another chromosome
• chromatids swap sections so they have a different combination of alleles but same genes

Question 2

Metaphase 1

Answer 2

• homologous pairs line up across centre of cell and attach to spindle fibres by centromeres
• homologous pairs arranged randomly (members of each pair face opposite poles) so arrangement is called independent assortment
• the order they line up determines how they will segregate independently during anaphase

Question 3

Anaphase 1

Answer 3

• spindles contract
• homologous pairs separated
• one chromosome goes to each end of the cell

Question 4

Telophase 1

Answer 4

• nuclear envelope forms around each group of chromosomes

- cytokinesis occurs forming 2 haploid daughter cells

Question 5

Prophase 2

Answer 5

• nuclear envelope breaks down

- spindles form

Question 6

Metaphase 2

Answer 6

• chromosomes attach to spindle by centromere

- order of attachment determines how chromatids separate during anaphase

Question 7

Anaphase 2

Answer 7

• centromeres divide
• chromatids of each chromosome pulled to opposite poles of spindle
• chromatids randomly separated

Question 8

Telophase 2

Answer 8

• nuclear envelope forms around each of 4 haploid nuclei

- in animals 2 cells divide to give 4

Question 9

Prophase 1

Answer 9

-chromosomes condense (shorter + fatter)
-chromosomes arrange into homologous pairs
-crossing over happens
-centrioles move to opposite ends of cell
-single fibres form
Nuclear envelope breaks down