Most humans (and vertebrates, in general) are genetically "programmed" to produce a brown skin pigment known as melanin. albinism--the inability to produce melanin—is inherited in humans as an autosomal recessive trait. an individual with genotype aa or aa will have normally pigmented skin, whereas an individual with genotype aa will produce no melanin. the albino's skin is very pale white, and the (highly vascularized) irises of the eyes appear red because no melanin obscures the red reflectance of blood.

Most humans (and vertebrates, in general) are genetically "programmed" to produce a brown skin pigment known as melanin. Albinism--the inability to produce melanin—is inherited in humans as an autosomal recessive trait. An individual with genotype AA or Aa will have normally pigmented skin, whereas an individual with genotype aa will produce no melanin. The albino's skin is very pale white, and the (highly vascularized) irises of the eyes appear red because no melanin obscures the red reflectance of blood.

The frequencies aa (Parental genotype male) and Aa (Parental genotype female, predict the frequencies of all genotypes and phenotypes expected  to result from the cross of an albino male with a heterozygous female.

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convection currents in the magma drive plate tectonics. heat generated from the radioactive decay of elements deep in the interior of the earth creates magma (molten rock) in the aesthenosphere. the aesthenosphere (70 ~ 250 km) is part of the mantle, the middle sphere of the earth that extends to 2900 km.