Question

Match the following mechanisms that produce variation in chromosome number with the phenotypic result:

1. Meiotic Nondisjunction
2. Mitotic Nondisjunction
3. Interspecies Crosses

Answer 1

Genetic variation is created through crossing-over and independent assortment during meiosis, resulting in numerous combinations of genetic material.

Step-by-step explanation:

Genetic variation in organisms is largely due to mechanisms that occur during meiosis. During meiosis I, homologous chromosomes undergo crossing-over, where non-sister chromatids exchange DNA segments, creating new combinations of genes. This, along with independent assortment of chromosomes—where the orientation of homologous pairs is random at the metaphase plate—results in a vast number of possible chromosome arrangements. With humans having 23 pairs of chromosomes, this leads to over 8 million different combinations from independent assortment alone, not including the variation introduced by crossing-over.

Meiotic nondisjunction is an error that can occur when homologous chromosomes or sister chromatids fail to separate properly. This can result in gametes with an abnormal number of chromosomes. Mitotic nondisjunction can happen during cell division after fertilization, leading to cells with different chromosome numbers—a condition known as mosaicism.