Question

In human beings, multiple genes are involved in the inheritance of
a. Color blindness
b. Phenylketonuria
c. Sickle-cell anemia
d. Skin Color

Answer 1

Hint: Genetic inheritance is the principle of genetics. It is the result of inheritance that offspring acquire certain traits from the parents. These traits are determined by genes. Genes are the functional unit of hereditary which are present on chromosomes and are composed of DNA or RNA.

Complete answer:
As you must know about how Gregor Mendel worked on the pea plants and discovered the laws of inheritance. Inherited traits are passed from parents to offspring, and result in similar eye color, hair color, height, etc.

Multiple gene inheritance or polygenic inheritance is when one trait or characteristic is controlled by multiple genes. In humans, polygenic inheritance results in skin pigmentation. About sixty loci contribute to inheritance of one characteristic.

Hence, the correct answer is option (b).

Additional information:
The variety of skin color is due to three pigments: melanin, carotene, hemoglobin. Melanin is the primary pigment that determines the skin color. It is synthesized in the melanocytes present in the skin and protects the skin from UV rays. Further, melanin is categorized into two categories- eumelanin and pheomelanin. Imbalance in production of melanin in skin can lead to various types of skin disorders.

Note: Polygenic inheritance not only occurs in humans but also occurs in plants. In plants, it determines the shape and color of stems, size of seed, yield. For example, in length of corolla in tobacco, 5 genes are involved in the expression of phenotype for this. Also, in kernel color of wheat polygenic inheritance is applicable as three independent alleles express its color.