The most common cause of both trisomy and monosomy is
A) exposure to radiation.
B) carcinogenic agents.
C) smoking.
D) nondisjunction.
E) None of these are the most common cause of trisomy and monosomy.

Question

Quizplus · Accepted Answer

Nondisjunction is the most common cause of both trisomy (in which there are three copies of a chromosome) and monosomy (in which there is only one copy of a chromosome). Nondisjunction occurs during meiosis when chromosomes fail to separate properly, resulting in gametes with an abnormal number of chromosomes. When these gametes fuse during fertilization, the resulting zygote will have an abnormal number of chromosomes. This can lead to disorders such as Down syndrome, Turner syndrome, and Klinefelter syndrome. Radiation, carcinogenic agents, and smoking can increase the risk of genetic mutations and chromosomal abnormalities, but are not the most common cause of trisomy or monosomy specifically. Therefore, the correct answer is D.

The Most Common Cause of Both Trisomy and Monosomy Is