Nondisjunction during meiosis results in which of the following?

• A. Normal division of chromosomes
• B. Homologous chromosomes fail to separate
• C. Crossing over fails
• D. Chromosome deletion occurs

Answer: (B)

Nondisjunction is when chromosomes don’t separate properly during meiosis. The best description is that homologous chromosomes fail to separate during meiosis I, which leaves one gamete with an extra chromosome and another missing one. This mismatched separation creates aneuploid gametes that can lead to conditions like trisomy or monosomy in the offspring.

Crossing over is genetic recombination during prophase I and is not about separation of chromosomes, so it’s not what nondisjunction describes. Normal division would mean chromosomes separate correctly. A chromosome deletion is a structural change in the chromosome, not a failure of the chromosomes to separate during meiosis.