Advanced Placement (AP) Biology Practice Exam

Which term describes an error where an organism has multiple sets of chromosomes instead of pairs?

1. Monosomy

2. Aneuploidy

3. Polyploidy

4. Trisomy

The correct answer is: Polyploidy

The term that describes an error where an organism has multiple sets of chromosomes instead of pairs is polyploidy. Polyploidy occurs when an organism has more than two complete sets of chromosomes. This condition is common in plants and can arise due to various mechanisms, such as failure during meiosis, leading to gametes that carry extra chromosome sets. When these gametes fuse during fertilization, the resulting offspring can have multiple sets of chromosomes, resulting in a polyploid organism. In contrast, monosomy refers to the presence of only one chromosome from a pair, aneuploidy encompasses any variation from the normal diploid number, including both additional and missing chromosomes, and trisomy specifically denotes the presence of an extra chromosome in one of the pairs, leading to three chromosomes instead of the typical two. These other terms relate to more specific numerical changes in chromosome number rather than the condition of having multiple complete sets.