Question

A person with Down Syndrome has an additional #21 chromosome in every somatic cell. This condition is also called trisomy 21. The cause of this syndrome A) is not known B) is due to crossing over of genes during Prophase 1 of meiosis C) is through the union of a normal gamete with the haploid amount of chromosomes (n) and another gamete with an extra #21 (n + 1) D) is through a mutation during DNA replication of mitosis in a somatic cell, and this mutation spreads to all other somatic cells in the body

Answer 1

Down Syndrome is caused by the union of a normal gamete with a gamete that has an extra chromosome 21, a condition resulting from chromosomal nondisjunction during meiosis.

Step-by-step explanation:

The cause of Down Syndrome, which is characterized by the presence of an additional chromosome 21 in every somatic cell (also known as trisomy 21), is through the union of a normal gamete with the haploid amount of chromosomes (n) and another gamete with an extra #21 (n + 1). This occurs due to a process called chromosomal nondisjunction during meiosis, which is the most common cause of this syndrome. Trisomy 21 leads to a variety of physical and developmental features, and the risk increases with maternal age, particularly in women over 36 years old.