2.3.2 meiosis

Question 1

what is meiosis

Answer 1

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

Question 2

what do chromosomes typically appear as in diploid cells

Answer 2

homologous pairs

Question 3

what are homologous chromosomes

Answer 3

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

Question 4

what do the chromosomes that replicated prior to meiosis I each consist of

Answer 4

two genetically identical chromatids attached at the centromere

Question 5

describe meiosis I

Answer 5

• the chromosomes which have replicated prior to meiosis I each consist of two genetically identical chromatids attached at the centromere
• 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
• linked genes are those on the same chromosomes. crossing over can result in new combinations of the alleles of these genes
• this crossing over of DNA is random and produces genetically different recombinant chromosomes
• spindle fibres attach to the homologous pairs and line them up at the equator of the spindle
• the orientation of the pairs of homologous chromosomes at the equator is random
• chromosomes of each homologous pair are separated and move toward opposite poles
• cytokinesis occurs and two daughter cells form

Question 6

what is meant by independent assortment

Answer 6

this is when each pair of chromosomes is positioned independently of the other pairs, irrespective of their maternal and paternal origin

Question 7

describe meiosis II

Answer 7

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