The allele for red hair is recessive to the allele for black hair. What colour hair will a person have if he inherits an allele for red hair from his mother and an allele for black hair from his father?

Black hair

Explanation:

(In most cases) A child from red+black haired parents would have black hair. The allele for black hair is dominant to that of red, and would be the phenotype of the hair.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)

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