NEET BIOLOGY

Detailed explanation-1: -Crossing over takes place at the pachytene stage of prophase I of Meiosis. Crossing over includes the symmetrical division of chromatids, and the reciprocal exchange and crosswise assembly of segments between non-sister chromatids, often breaking linkage. This results in the recombination of genes.

Detailed explanation-2: -Crossing over occurs only during prophase I. The complex that temporarily forms between homologous chromosomes is only present in prophase I, making this the only opportunity the cell has to move DNA segments between the homologous pair.

Detailed explanation-3: -Explanation: The crossing over of homologous chromosomes occurs in prophase I of meiosis. Prophase I of meiosis is characterized by the lining up of homologous chromosomes close together to form a structure known as a tetrad. A tetrad is composed of four chromatids.

Detailed explanation-4: -During meiosis, crossing-over occurs at the pachytene stage, when homologous chromosomes are completely paired.

Detailed explanation-5: -In prophase, I, two copies of each gene are present on homologous chromosomes but in prophase II copies of each gene are present on sister chromatids within a single chromosome. As a result, any crossing over in prophase II would produce two identical chromatids. So the crossing over does not take place in prophase II.