The production of offspring by sexual reproduction includes fusion of male and female gametes. Gamet

Question

The production of offspring by sexual reproduction includes fusion of male and female gametes. Gametes are haploid cells formed from diploid cells. The specialised kind of cell division that reduces the chromosome number by half results in the production of haploid daughter cells called meiosis. The statements describing prophase I of meiosis coinciding with different stages of prophase I are given below.\ P - Thin thread-like chromosomes with a beaded appearance
Q - Appearance of recombination nodules
R - Formation of bivalents/tetrads
S - Terminalisation of chiasmata
T -Appearance of chiasmata \ Identify the stage from the given statements in which crossing over occurs.\

Professor PC Thomas Classes · Answer

(a) : Crossing over is the process of exchange of genetic material between non-sister chromatids of two homologous chromosomes. It is an enzyme-mediated process and occurs during pachytene sub-stage of prophase I.