AP BIOLOGY

Detailed explanation-1: -Tetrads are formed in prophase I of meiosis I. Tetrad consist of two homologous chromosomes, each with two chromatids. Thus, a tetrad consists of 4 chromatids, two of which belong to each chromosome called sister chromatids which are joined at the centromere.

Detailed explanation-2: -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. Metaphase I: The tetrads line up along the metaphase plate.

Detailed explanation-3: -At the end of prophase I, the pairs are held together only at the chiasmata; they are called tetrads because the four sister chromatids of each pair of homologous chromosomes are now visible.

Detailed explanation-4: -The nucleus contains 23 homologous chromosome pairs. Each chromosome is made of two sister chromatids (copies). The cells begin to divide, and the chromosomes pair up, forming a structure called a tetrad, which contains four chromatids.

Detailed explanation-5: -Each pair of chromosomes-called a tetrad, or a bivalent-consists of four chromatids. At this point, the homologous chromosomes exchange genetic material by the process of crossing over (see linkage group).