What genetic error occurs when chromosomes fail to separate during meiosis?

What genetic error occurs when chromosomes fail to separate during meiosis?

• A. Pedigree
• B. Nondisjunction
• C. Restriction Enzyme
• D. Gel Electrophoresis

Answer: (B)

Nondisjunction during meiosis is the genetic error described here: chromosomes fail to separate properly, so gametes end up with too many or too few chromosomes. Normally, homologous chromosomes separate in meiosis I and sister chromatids separate in meiosis II. When separation doesn’t occur, one gamete can receive an extra chromosome while another ends up missing one. If such a gamete contributes to fertilization, the resulting zygote has an abnormal chromosome number (aneuploidy), such as trisomy or monosomy. That’s why this term is the best fit for the described situation, since it directly explains the mechanism behind the chromosomal imbalance. Pedigree is simply a family-tree representation of inheritance, not an error during meiosis. Restriction enzymes cut DNA at specific sequences, and gel electrophoresis separates DNA fragments by size—both are laboratory techniques, not meiotic errors.

Nondisjunction during meiosis is the genetic error described here: chromosomes fail to separate properly, so gametes end up with too many or too few chromosomes. Normally, homologous chromosomes separate in meiosis I and sister chromatids separate in meiosis II. When separation doesn’t occur, one gamete can receive an extra chromosome while another ends up missing one. If such a gamete contributes to fertilization, the resulting zygote has an abnormal chromosome number (aneuploidy), such as trisomy or monosomy. That’s why this term is the best fit for the described situation, since it directly explains the mechanism behind the chromosomal imbalance.

Pedigree is simply a family-tree representation of inheritance, not an error during meiosis. Restriction enzymes cut DNA at specific sequences, and gel electrophoresis separates DNA fragments by size—both are laboratory techniques, not meiotic errors.