The INDIVIDUALIST

A Wiki about biochemical individuality

Polymorphism

Description

Mahunage, (1962) showed that the consistency of ear-wax is under genetic control. Cerumen (ear-wax) may be wet (sticky) or dry (hard); the types are controlled by a pair of allelic genes, that for the wet type expressing itself dominantly in relation to that for the dry.

Asians and Native Americans are more likely to have the dry type of cerumen (grey and flaky), whereas Caucasians and Africans are more likely to have the wet type (honey-brown to dark-brown and moist). Cerumen type has been used by anthropologists to track human migratory patterns, such as those of the Inuit.

The difference in cerumen type has been tracked to a single base change (an SNP) in a gene known as "ATP-binding cassette C11 gene". In addition to affecting cerumen type, this mutation also reduces sweat production. The researchers conjecture that the reduction in sweat was beneficial to the ancestors of East Asians and Native Americans who are thought to have lived in cold climates.

Petrakis et al. (1971) summing up his own observations and those of others on the distribution of the alleles, showed that them are wide variations in gene frequencies throughout the world, the dry allele being predominant in the Mongoloid peoples; in Caucasoids the wet allele usually predominates, and in Negroids the dry allele is almost totally absent.

Discussion

Since the cerumen glands of the ear and the mammary glands are both derived from the apocrine type of sweat glands, attempts have been made to show an association between carcinoma of the breast and wax type.

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