Down syndrome is a genetic disorder that results from A)the presence of an extra 21^st chromosome. B)an autosomal recessive gene. C)a sex-linked dominant gene. D)a specific combination of three recessive genes. E)the presence of three sex chromosomes usually XXY.

Question

Quizplus · Accepted Answer

Down syndrome is caused by the presence of an extra 21st chromosome (Trisomy 21). This extra copy of genetic material causes developmental and physical abnormalities. It is not caused by a specific combination of recessive genes, autosomal or sex-linked genes.

Down Syndrome Is a Genetic Disorder That Results from