Which genetic condition is caused by an extra copy of chromosome 21 and results in intellectual disability?

Which genetic condition is caused by an extra copy of chromosome 21 and results in intellectual disability?

• A. Fragile X syndrome
• B. Down Syndrome
• C. Turner syndrome
• D. Williams syndrome

Answer: (B)

Down syndrome is a genetic condition characterized by the presence of an extra copy of chromosome 21, resulting in chromosomal abnormality known as trisomy 21. This additional genetic material alters the development of the body and brain, leading to various physical features and intellectual disabilities. Children and adults with Down syndrome may also experience certain health issues, but the hallmark of the condition often involves cognitive challenges. The presence of an extra chromosome affects the typical developmental processes, resulting in the observable features commonly associated with Down syndrome and varying degrees of intellectual disability. The other genetic conditions listed do not involve an extra copy of chromosome 21. For instance, fragile X syndrome is linked to mutations in the FMR1 gene on the X chromosome and is associated with developmental issues but is not caused by a chromosomal trisomy. Turner syndrome is a condition that occurs in females who have a missing or incomplete X chromosome, leading to various physical and developmental challenges. Williams syndrome, caused by a deletion of genetic material from chromosome 7, features distinct cognitive profiles and social behaviors but does not involve an extra chromosome 21. Thus, Down syndrome is the one condition mentioned in the choices that directly relates to the additional chromosome and resulting intellectual disability.

Down syndrome is a genetic condition characterized by the presence of an extra copy of chromosome 21, resulting in chromosomal abnormality known as trisomy 21. This additional genetic material alters the development of the body and brain, leading to various physical features and intellectual disabilities. Children and adults with Down syndrome may also experience certain health issues, but the hallmark of the condition often involves cognitive challenges. The presence of an extra chromosome affects the typical developmental processes, resulting in the observable features commonly associated with Down syndrome and varying degrees of intellectual disability.

The other genetic conditions listed do not involve an extra copy of chromosome 21. For instance, fragile X syndrome is linked to mutations in the FMR1 gene on the X chromosome and is associated with developmental issues but is not caused by a chromosomal trisomy. Turner syndrome is a condition that occurs in females who have a missing or incomplete X chromosome, leading to various physical and developmental challenges. Williams syndrome, caused by a deletion of genetic material from chromosome 7, features distinct cognitive profiles and social behaviors but does not involve an extra chromosome 21. Thus, Down syndrome is the one condition mentioned in the choices that directly relates to the additional chromosome and resulting intellectual disability.