AP BIOLOGY

Detailed explanation-1: -Non-disjunction involving the X-chromosome may occur during oogenesis and produce two kinds of eggs. If normal sperm fertilize these two types, which of the following pairs of genotypes are possible? A new plant arises in your garden. The chromosome complement is determined to be 4n, a tetraploid.

Detailed explanation-2: -According to Bridges’s hypothesis, during nondisjunction in the females, their two X chromosomes do not separate to form normal eggs with a single X chromosome each. Instead, nondisjunction creates eggs with either two X chromosomes or with none.

Detailed explanation-3: -Nondisjunction is the failure of homologous chromosomes to disjoin correctly during meiosis. This results in the production of gametes containing a greater or lesser chromosomal amount than normal ones. Consequently the individual may develop a trisomal or monosomal syndrome.

Detailed explanation-4: -Meiotic nondisjunction, particularly in oogenesis, is a common mutational mechanism, responsible for chromosomally abnormal fetuses. In those fetuses that survive to term, chromosome abnormalities cause developmental defects, failure to thrive, and reduced mental function. Mitotic nondisjunctions can also be inherited.