AP BIOLOGY

Detailed explanation-1: -When homologous chromosomes form pairs during prophase I of meiosis I, crossing-over can occur. Crossing-over is the exchange of genetic material between homologous chromosomes. It results in new combinations of genes on each chromosome.

Detailed explanation-2: -During crossing over, homologous chromosomes come together in order to form a tetrad. This close contact allows the nonsister chromatids from homolgous chromosomes to attach to one another and exchange nucleotide sequences.

Detailed explanation-3: -Between prophase I and metaphase I, the pairs of homologous chromosome form tetrads. Within the tetrad, any pair of chromatid arms can overlap and fuse in a process called crossing-over or recombination.

Detailed explanation-4: -The formation of tetrads is also called synapsis. Something very important about tetrads is that they enable the homologous chromosomes to exchange segments of DNA, a process called crossing over . This process increases the genetic variation of the gametes.

Detailed explanation-5: -Homologous pair of chromosomes that are close to each other and form a synaptonemal complex is called a tetrad. During synapsis, the homologous pairs of sister chromatids line up together and connect. Within the tetrad, any pair of chromatid arms can overlap and fuse in a process called crossing-over or recombination.