Which of the following statements applies to the variation in human skin color?

• A. It is determined by a single gene with two alleles.
• B. It is not affected by environmental factors such as sunlight.
• C. It is a polygenic trait influenced by multiple genes.
• D. It shows no continuous variation within populations.

Answer: (C)

Verified step by step guidance

1. Understand the concept of polygenic traits: Polygenic traits are controlled by multiple genes, each contributing to the phenotype. Human skin color is an example of such a trait, influenced by several genes that determine the amount and type of melanin produced in the skin.
2. Recognize the role of environmental factors: Human skin color is also affected by environmental factors, such as exposure to sunlight, which can increase melanin production and temporarily darken the skin.
3. Identify continuous variation: Polygenic traits like skin color exhibit continuous variation, meaning there is a wide range of phenotypes rather than distinct categories. This is why human skin color varies gradually across populations.
4. Eliminate incorrect statements: The statement 'It is determined by a single gene with two alleles' is incorrect because skin color is polygenic. The statement 'It is not affected by environmental factors such as sunlight' is also incorrect because sunlight influences melanin production. The statement 'It shows no continuous variation within populations' is incorrect because skin color does show continuous variation.
5. Conclude with the correct statement: The correct answer is 'It is a polygenic trait influenced by multiple genes,' as this accurately describes the genetic basis and variation of human skin color.