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Human skin colour is described in NCERT as a polygenic trait because:
AA single gene with two alleles controls the entire phenotypic spectrum from light to dark
BA single gene with multiple alleles such as A1, A2, A3 acts in a stepwise fashion
CThree or more genes act additively, with environmental factors also contributing
DTwo genes show classical Mendelian dominance giving distinct dark and light classes
Answer & Solution
Correct answer: A. A single gene with two alleles controls the entire phenotypic spectrum from light to dark
Polygenic traits are controlled by three or more genes whose effects add up, and the environment also contributes. Each dominant allele adds to the darker phenotype in the AABBCC type model.
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