Question

Which of the statements best describes the process of crossing over during meiosis? Haploid daughter cells trade chromosomes in pairs. Homologous chromosomes pair up and exchange segments of DNA. Chromosomes trade genes with other nearby chromosomes at random. Pairs of homologous chromosomes separate and move to opposite sides of the cell.

Answer 1

Homologous chromosomes pair up and exchange segments of DNA.

Option A

Explanation:

Crossing over is an event of Prophase 1 of meiosis 1. It occurs in the zygotene phase of prophase 1. Here the homologous chromosome pairs get very close together and gets packed within protein coat. The enzymes randomly cut the DNA segments from both chromosomes at same loci and exchange them with each other. This results in the exchange of genes between the two chromosomes. This is how the variation comes to place between offsprings of the same individuals. The crossing over results to form X shaped intersections between homologous pair of chromosomes which is called as chaismata. This phase occurs in pachytene phase and is visible in diplotene phase when the protein coat dissolves.