During which phase do bivalents form in meiosis?

During which phase do bivalents form in meiosis?

• A. Prophase 2
• B. Prophase 1
• C. Metaphase 2
• D. Telophase 2

Answer: (B)

Bivalents, also known as tetrads, form during prophase 1 of meiosis. This stage is characterized by the pairing of homologous chromosomes, where each pair consists of two chromosomes, each with two sister chromatids. The physical pairing of these homologous chromosomes is crucial for the processes of genetic recombination and reduction in genetic content that are indicative of meiosis. During this phase, the chromosomes condense and become visible, and the process of synapsis occurs, allowing homologous chromosomes to align closely together, forming bivalents. This sets the stage for crossing over, where segments of genetic material are exchanged between the homologous chromosomes, increasing genetic diversity in the resulting gametes. The other phases mentioned in the options do not involve the formation of bivalents. In prophase 2, the cells are already haploid and do not form homologous pairs. Metaphase 2 involves individual chromosomes aligning at the cell equator without being paired as bivalents. Finally, telophase 2 marks the end of meiosis, where the separated chromosomes reach opposite poles and begin to decondense, finalizing the formation of the four haploid cells, with no bivalent structures present.

Bivalents, also known as tetrads, form during prophase 1 of meiosis. This stage is characterized by the pairing of homologous chromosomes, where each pair consists of two chromosomes, each with two sister chromatids. The physical pairing of these homologous chromosomes is crucial for the processes of genetic recombination and reduction in genetic content that are indicative of meiosis.

During this phase, the chromosomes condense and become visible, and the process of synapsis occurs, allowing homologous chromosomes to align closely together, forming bivalents. This sets the stage for crossing over, where segments of genetic material are exchanged between the homologous chromosomes, increasing genetic diversity in the resulting gametes.

The other phases mentioned in the options do not involve the formation of bivalents. In prophase 2, the cells are already haploid and do not form homologous pairs. Metaphase 2 involves individual chromosomes aligning at the cell equator without being paired as bivalents. Finally, telophase 2 marks the end of meiosis, where the separated chromosomes reach opposite poles and begin to decondense, finalizing the formation of the four haploid cells, with no bivalent structures present.