AP BIOLOGY

Detailed explanation-1: -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-2: -Prophase I DNA replication precedes the start of meiosis I. During prophase I, homologous chromosomes pair and form synapses, a step unique to meiosis. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent.

Detailed explanation-3: -Importantly, homologous chromosomes pair up, which is unique to prophase I. In prophase of mitosis and meiosis II, homologous chromosomes do not form pairs in this way. Crossing over occurs during this phase. Metaphase I: Spindle fibers attach to the paired homologous chromosomes.

Detailed explanation-4: -Prophase is the first stage in mitosis, occurring after the conclusion of the G2 portion of interphase. During prophase, the parent cell chromosomes-which were duplicated during S phase-condense and become thousands of times more compact than they were during interphase.