Question

what must homologous chromosomes form so that crossing over may occur? tetrads mutated dna equator alignment centromeres

Explanation:

During meiosis, homologous chromosomes pair up. This pairing forms tetrads (also known as bivalents). Crossing - over (exchange of genetic material between non - sister chromatids of homologous chromosomes) occurs when homologous chromosomes are in the tetrad form. Mutated DNA is not a structure formed for crossing - over. Equator alignment (chromosomes aligning at the metaphase plate) is a stage in cell division but not the structure for crossing - over. Centromeres are the regions that hold sister chromatids together and are not directly related to the structure for crossing - over.

Answer:

tetrads