Question

In human beings, multiple genes are involved in the inheritance of:

• A. skin color
• B. sickle­ cell anemia
• C. phenylketonuria
• D. color blindness

Answer 1

The correct option is A

skin color

The correct option is A.

Explanation of Correct option:

1. Multiple genes are two or more pairs of non-allelic genes, which are present on different loci but influence the same phenotypic trait and have an additive effect.
2. Skin color is one such trait that is inherited by multiple genes.
3. Skin color depends on the presence of melanin pigment which is determined by three pairs of genes namely A, B, and C
4. These are present on different loci and each is responsible for synthesizing a fixed amount of melanin. Thus the effect of all these three genes is additive.

Explanation of Incorrect option:

Option B:

1. Sickle cell anemia is a disease that is caused due to codominance.
2. In codominance both the alleles express themselves in F₁ hybrids.
3. The red blood cells become sickle-shaped.

Option C:

1. Phenylketonuria is caused due to pleiotropy.
2. In pleiotropy, a single pair of genes influences more than one character.
3. Phenylketonuria is an autosomal recessive disorder that is caused by the mutant gene present on the 12th chromosome.
4. The mutant gene fails to code for Phenylalanine hydroxylase needed for normal metabolism of phenylalanine to tyrosine.
5. Accumulated phenylalanine causes severe brain damage.

Option D:

1. Color blindness is an X-linked recessive disorder.
2. It happens only in males as males have only one X chromosome.

Final Answer: In human beings, multiple genes are involved in the inheritance of skin color.