2.3 b Meiosis

Question 1

What is the definition if meiosis?

Answer 1

The division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte

Question 2

How do chromosomes in a diploid cells typically appear?

Answer 2

as homologous pairs

Question 3

What are homologous chromosomes?

Answer 3

chromosomes that are the same size, same centromere position and with the same sequence of genes at the same loci

Question 4

Explain the chromosomes at meiosis I?

Answer 4

• they have replicated prior to meiosis I
• each consist of two genetically identical chromatids attached at the centromere

Question 5

What is the process of meiosis I?

Answer 5

• the chromosomes condense and the homologous chromosomes pair up
• chiasmata form at points of contact between the non-sister chromatids of a homologous pair and sections of DNA are exchanged
• spindle fibres attach to the homologous pairs and line them up at the equator of the spindle
• the chromosomes of each homologous pair are separated and move towards opposite poles
• cytokinesis occurs and two daughter cells form

Question 6

What are linked genes?

Answer 6

those that are on the same chromosome

Question 7

What can crossing over result in?

Answer 7

new combinations of the alleles of these genes

the crossing over of DNA is random and produces genetically different recombinant chromosomes

Question 8

What is independent assortment

Answer 8

• the orientation of the pairs of homologous chromosomes at the equator is random
• each pair of homologous chromosomes is positioned independently of the other pairs, irrespective of their maternal and paternal origin

Question 9

Explain meiosis II

Answer 9

• each of the two cells produced in meiosis I undergoes a further division during which the sister chromatids of each chromosome are separated
• a total of 4 haploid cells are produced

Question 10

How many cells are produced in meiosis II and describe them

Answer 10

4 haploid cells