Which of the following statements about genes and alleles is correct? MCQ with Answer and Explanation

Explanation:
Rickets is characterized by defective mineralization of bones, leading to bowed legs, soft skull, and skeletal deformities due to vitamin D deficiency in children. In adults, deficiency causes osteomalacia. Scurvy is vitamin C deficiency, pellagra is niacin deficiency, beri-beri is thiamine deficiency. Vitamin D (calciferol) promotes calcium and phosphorus absorption from the gut. Sunlight exposure helps synthesize vitamin D in skin.

Explanation:
Streptomycin is produced by Streptomyces griseus, a soil actinobacterium. Penicillium is a mold producing penicillin, Bacillus species produce some antibiotics like bacitracin, Aspergillus produces other substances.

Explanation:
Pleiotropy occurs when a single gene affects two or more distinct phenotypic traits. This happens because the gene product (protein) may be used in multiple biological pathways or expressed in different tissues. Examples include phenylketonuria (PKU), sickle cell anemia, and Marfan syndrome. Epistasis involves the interaction of different genes, polygenic inheritance involves multiple genes affecting one trait, and incomplete dominance is a single gene interaction.