Agene family that codes for various hormone receptors has been accumulating nucleotide substitutions at a rate of 0.4 per million years. on average, there have been 60 substitutions between the common ancestor of this gene family and each of the various living forms of this gene. based on these figures, this hormone receptor gene family likely originated million years ago.

150 million years ago

Explanation:

Data provided in the question:

Rate accumulating nucleotide substitutions = 0.4 per million years

Substitutions between the common ancestor of the gene family = 60

Now,

Let the hormone receptor gene family likely to be originated N million years ago.

we know

Rate accumulating nucleotide substitutions × N = Substitutions between the common ancestor of the gene family

Therefore,

0.4 × N = 60

or

N = [ 60 ÷ 0.4 ] million years

or

N = 150 million years

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answer: b

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