AP BIOLOGY

Detailed explanation-1: -During prophase I, the homologous chromosomes condense and become visible as the x shape we know, pair up to form a tetrad, and exchange genetic material by crossing over. During prometaphase I, microtubules attach at the chromosomes’ kinetochores and the nuclear envelope breaks down.

Detailed explanation-2: -Tetrad formation occurs during the zygotene stage of meiotic prophase. It is a meiotic-specific process. Homologous chromosomes are DNA fragments within a diploid organism of the same size one from each parental source.

Detailed explanation-3: -Prophase I: The nuclear envelope breaks down. The chromatin condenses into chromosomes. Homologous chromosomes containing the two chromatids come together to form tetrads, joining at their centromeres (2n 4c). This is when “crossing over” occurs, which creates genetic variation.

Detailed explanation-4: -During prophase I, the pairs of homologous chromosomes come together to form a tetrad or bivalent, which contains four chromatids. Recombination can occur between any two chromatids within this tetrad structure.

Detailed explanation-5: -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. Recombination is a process that breaks, recombines and rejoins sections of DNA to produce new combinations of genes.