Question

Find the incorrect statement among the following: n(A) In sex-linked recessive traits, the gene is transmitted from an unaffected carrier female to some of the male progeny. n(B) Accumulation of phenylpyruvic acid in the brain results in mental retardation. n(C) Individuals affected by Down’s Syndrome will have congenital heart defects and are more intelligent. n(D) Turner’s Syndrome is caused due to the absence of one X chromosome.

• A. In sex-linked recessive traits, the gene is transmitted from an unaffected carrier female to some of the male progeny.
• B. Accumulation of phenylpyruvic acid in the brain results in mental retardation.
• C. Individuals affected by Down’s Syndrome will have congenital heart defects and are more intelligent.
• D. Turner’s Syndrome is caused due to the absence of one X chromosome.

Hint:

Accurate knowledge of genetic disorders aids in diagnosis and management.

Answer 1

The Correct Option is C

The incorrect statement is: Individuals affected by Down's Syndrome will have congenital heart defect and are more intelligent.

(A) Sex-linked inheritance - Correct: Carrier females (X^HX^h) can transmit recessive traits (e.g., hemophilia) to male offspring (X^hY).

(B) Phenylpyruvic acid accumulation - Correct: This is characteristic of phenylketonuria (PKU), causing intellectual disability if untreated.

(C) Down's Syndrome description - Incorrect: While congenital heart defects occur in ~50% cases, individuals typically have mild to moderate intellectual disability (not increased intelligence).

(D) Turner's Syndrome - Correct: 45,X karyotype (missing one X chromosome) causes this condition.

The incorrect statement is (C), as it contains a factual error regarding cognitive abilities in Down's Syndrome (Trisomy 21).

Answer 2

Down’s syndrome is caused by an extra copy of chromosome 21 (trisomy 21). It is associated with intellectual disability, developmental delays, and physical features like a flattened face and a shorter neck.

A common issue in individuals with Down’s syndrome is congenital heart defects.

However, the statement that individuals with Down's syndrome are more intelligent is incorrect. Most individuals with Down's syndrome have mild to moderate intellectual disability, not greater intelligence.

Other Statements:

(A): X-linked recessive traits are indeed carried by females and passed to male offspring.

(B): Accumulation of phenylpyruvic acid in the brain causes mental retardation in conditions like phenylketonuria (PKU).

(D): Turner’s syndrome is indeed caused by the absence of one X chromosome.

Option (C) is incorrect because individuals with Down’s syndrome typically have lower intelligence, not higher.