What term describes paired homologous chromosomes that come together during prophase I?

• A. Chromatids
• B. Chromosomes
• C. Tetrads
• D. Genes

Answer: (C)

During prophase I of meiosis, homologous chromosomes pair up in a process called synapsis. This paired set is called a tetrad (also known as a bivalent). A tetrad consists of four chromatids—two sister chromatids for each of the homologous chromosomes in the pair. This close association is what enables crossing over between non-sister chromatids, promoting genetic variation in gametes. So the term for paired homologous chromosomes that come together is tetrad.

Chromatids are the identical copies that make up a replicated chromosome, not the paired set of homologs. Chromosomes can refer to a single DNA molecule (or a replicated one with two sister chromatids) and don’t specify the pairing of homologs. Genes are the specific sequences of DNA located on chromosomes that encode traits, not the physical structure formed by pairing during prophase I.