Meiosis

Question 1

what occurs during prophase 1

Answer 1

chromosomes condense, the nuclear envelope disintegrates, the nucleolus disappears and spindle formation begins, crossing over occurs

Question 2

what is crossing over

Answer 2

prophase 1, the homologous chromosomes pair up forming bivalents, moving them through the cytoplasm results in chromatids entangling, creating genetic variation

Question 3

What occurs in metaphase 1

Answer 3

the same as metaphase in mitosis except the homologous pairs of chromosomes line up along the metaphase plate instead of the individual chromosomes, independent assortment

Question 4

what is independent assortment

Answer 4

metaphase 1, random orientation of each homologous pair on the metaphase plate is random and and independent of any other homologous pair, can result in many different combinations of alleles facing the poles, results in genetic variation

Question 5

what occurs in anaphase 1

Answer 5

different from mitosis as homologous chromosomes are pulled to the poles and the chromatids stay together, chromatids break off and rejoin sometimes resulting in exchange of DNA, chiasmata are points where they rejoin, forms recombinant chromatids with genes being exchanged, causes genetic variation

Question 6

what occurs in telophase 1

Answer 6

same as telophase in mitosis, chromosomes assemble at each pole and the nuclear membrane reforms, chromosomes uncoil, cytokinesis occurs where the cell divides into two

Question 7

what occurs in prophase 2

Answer 7

chromosomes still consist of two chromatids, they condense and become visible again, nuclear envelope breaks down and spindle fibres form

Question 8

what occurs in metaphase 2

Answer 8

differs from 1, the individual chromosomes assemble on the metaphase plate, due to crossing over the chromatids are no longer identical so there is independent assortment again and more genetic variation produced

Question 9

what occurs in anaphase 2

Answer 9

results in chromatids of the individual chromosomes being pulled to opposite poles after division of the centromeres, same as in mitosis

Question 10

what occurs in telophase 2

Answer 10

chromatids assemble at the poles, chromosomes uncoil and form chromatin again, nuclear envelope and reforms and the nucleolus becomes visible