Asked by Natacha Espada on Apr 28, 2024
Verified
Down syndrome
A) is due to disjunction of chromosomes.
B) individuals have two number 21 chromosomes.
C) may occur at a lower rate in women over 40.
D) can occur if the sperm has an extra copy of chromosome 21.
E) persons have normal-appearing eyelids.
Down Syndrome
A genetic disorder caused by the presence of an extra 21st chromosome, leading to developmental and physical changes.
Disjunction
The separation of chromosomes or sister chromatids during cell division, leading to the distribution of genetic material into daughter cells.
Chromosome 21
One of the 23 pairs of human chromosomes, an extra copy of which is associated with Down syndrome.
- Describe the concepts of nondisjunction, trisomy, and monosomy and their effects on genetic disorders.
- Identify the genetic basis for chromosomal abnormalities such as Down syndrome and Turner syndrome.
Verified Answer
HK
Hadia KhalilMay 03, 2024
Final Answer :
D
Explanation :
Down syndrome is caused by an extra copy of chromosome 21, which can occur if either the sperm or the egg contributes an extra copy. This condition is not due to disjunction of chromosomes, but rather nondisjunction, where chromosomes fail to separate properly during cell division. Individuals with Down syndrome have three copies of chromosome 21, not two. The incidence of Down syndrome increases with maternal age, especially in women over 35, not lower. Persons with Down syndrome often have distinctive facial features, including eyelids that may appear slanted, contradicting the statement of normal-appearing eyelids.
Learning Objectives
- Describe the concepts of nondisjunction, trisomy, and monosomy and their effects on genetic disorders.
- Identify the genetic basis for chromosomal abnormalities such as Down syndrome and Turner syndrome.