CBSE Class 12-science Answered
Crossing over is the exchange of genetic material between two homologous chromosomes which occurs during the pachytene stage of meiosis I. It is catalysed by an enzyme called recombinase. The phenomenon of crossing over results in variations. Crossing over is not required for reductional division that takes place during meiosis. Hence, reductional division would take place irrespective of the effect of crossing over. Therefore, at the end of meiosis, 4 haploid cells would be formed. In this case, 2n=12; n=6. Thus, 4 haploid cells, each with n=6 chromosomes would be released. Although there is no crossing over, all the 4 haploid cells will not resemble each other as genetic variation occurs due to independent assortment.