Question

What happens during crossing over? Homologous chromosomes trade pieces of DNA. Sister chromatids form tetrads and line up randomly. Tetrads separate and produce two haploid daughter cells. Spindle fibers form and attach to centromeres.

Answer 1

Your answer would be A

Homologous chromosomes trade pieces of DNA.
When crossing over occurs, segments of non-sister chromatids break and then reattach to the other chromatid.

Answer 2

Homologous chromosomes trade pieces of DNA.

Step-by-step explanation:

Crossing over is a process which starts in pachytene stage of meiosis I. In crossing over, the non sister chromatids of homologous chromosomes of each parent exchange DNA segments so as to generate chromosomes with new combination of genes or we can say that the chromosomes formed after crossing over have different sequences of DNA than the parental one. When these chromosomes with new genetic make up are inherited in the progenies, the progenies have variations because they do not have exactly the same DNA sequence as of parents. The significance of crossing over is generation of variations among individuals of a species.