PATHOLOGY

Detailed explanation-1: -During prophase I, the pairs of homologous chromosomes come together to form a tetrad or bivalent, which contains four chromatids.

Detailed explanation-2: -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-3: -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.