AP BIOLOGY

Detailed explanation-1: -Crossing over is a cellular process that happens during meiosis when chromosomes of the same type are lined up. When two chromosomes-one from the mother and one from the father-line up, parts of the chromosome can be switched. The two chromosomes contain the same genes, but may have different forms of the genes.

Detailed explanation-2: -Crossing over does not occur in mitosis. Crossing over occurs in metaphase when all the chromosomes are aligned in the middle of the cell. Their close proximity allows crossing over to occur. Crossing over occurs in telophase right before the cells split since all the DNA and cell growth has occurred by this point.

Detailed explanation-3: -Answer and Explanation: Crossing over (recombination) only occurs during Prophase 1 of Meiosis because at this point homologous chromosomes line up at the centre of the cell.

Detailed explanation-4: -Crossing over occurs in meiosis but not mitosis because meiosis creates genetically unique cells and mitosis creates genetically identical cells. During meiosis in prophase I, crossing over occurs where homologous chromosomes exchange corresponding sections of DNA.