Question 1. The statement that 'Crossing over and the separation of duplicated homologous chromosomes in the first division produce genetic variation' is true. Crossing over is the exchange of genetic material between homologous chromosomes that occurs during meiosis. As the result, the daughter cells are genetically different from mother cells. It is one of the ways to produce genetic variation. Question 2. The nuclear envelope disintegrates during prophase. This is the process that occurs at the beginning of mitosis. During prophase, the first phase of mitosis, the chromosomes condense and the nuclear envelope disintegrates. At the end of mitosis, the chromosomes will decondense and the nuclear envelope will re-form.
