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Inheritance of skin colour in humans is an example of
A
point mutation
B
polygenic inheritance
C
codominance
D
chromosomal aberration
Detailed Solution
Human skin colour is not controlled by a single gene; it is controlled by three (or more) genes, say A, B and C.
Such traits, which are controlled by several genes, are called polygenic traits.
The dominant alleles A, B and C add to the amount of melanin, and the effect of each allele is additive.
The genotype with all dominant alleles (AABBCC) has the darkest skin colour and the one with all recessive alleles (aabbcc) has the lightest; the genotype with three dominant and three recessive alleles has an intermediate colour.
The phenotype therefore shows continuous gradation instead of sharp classes. Human height is another example.
It is not due to a point mutation, codominance or a chromosomal aberration.
So the inheritance of skin colour in humans is an example of polygenic inheritance.
Such traits, which are controlled by several genes, are called polygenic traits.
The dominant alleles A, B and C add to the amount of melanin, and the effect of each allele is additive.
The genotype with all dominant alleles (AABBCC) has the darkest skin colour and the one with all recessive alleles (aabbcc) has the lightest; the genotype with three dominant and three recessive alleles has an intermediate colour.
The phenotype therefore shows continuous gradation instead of sharp classes. Human height is another example.
It is not due to a point mutation, codominance or a chromosomal aberration.
So the inheritance of skin colour in humans is an example of polygenic inheritance.