Convergent Evolution to a Lighter Color
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Convergent Evolution to a Lighter Color

July 28, 2010
Whiptail and fence lizards are dark-colored on dark soil; however, when found on white sand they exhibit a light skin color that helps protect them from predators. It is a case of convergent evolution involving the same Mc1r gene coding for color. In the dark ancestral lizards, the gene codes for Mc1-receptors that help cells, called melanocytes, produce the melanin that makes the animal dark. In the white, sand-dwelling fence lizard, one copy of the mutation is sufficient to cause fewer Mc1-receptors to integrate into cell membranes, therefore resulting in a lighter color. In the whiptail lizards, the mutation is recessive and requires two copies of the gene. This combination does not affect the number of receptors integrated into cell membranes, but adversely affects their ability to transmit signal--arriving at the same result on the macro level: a lighter lizard.

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