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Name: Sandy
Status: Educator
Age: 50s
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Question:
How does one explain the difference between multiple alleles and polygenic inheritance?



Replies:
For the sake of simplicity, we usually teach genetics using examples with only two possible alleles (A and a). But a single gene can actually have many possible alleles (A, a, A1, A2, A', etc.). For example, hair color in mice is determined by a single gene with a series of alleles, each resulting in different coloration. There are alleles for black, brown, agouti, gray, albino, and others. The twist here is that the same allele can be dominant or recessive depending on context. Allelic series are often written as agouti > black > albino. This means that agouti is dominant to black, and black is dominant to albino. (And agouti is necessarily also dominant to albino.) If the black allele is in the presence of an agouti allele, the mouse will be agouti because black is recessive to agouti. If that same black allele is paired with an albino allele, the mouse will be black since black is dominant to albino.

Polygenic traits are the result of the interaction of several genes. For instance, phenotypes like high blood pressure (hypertension) are not the result of a single "blood pressure" gene with many alleles (a 120/80 allele, a 100/70 allele, a 170/95 allele, etc.) The phenotype is an interaction between a person's weight (one or more obesity genes), cholesterol level (one or more genes controlling metabolism), kidney function (salt transporter genes), smoking (a tendency to addiction), and probably lots of others too. Each of the contributing genes can also have multiple alleles.

Christine Ticknor
Ph.D. candidate
Yale University


Multiple alleles are different forms of the same gene...that is the sequence of the bases is slightly different in the genes lovcated on the same place of the chromosome. In polygenesis there is more than one gene involved and their may be multiple alleles of the multiple genes...which is far more complex...involving potentially a number chromosomes.

PF


Alleles are different versions or forms of ONE gene. For example, there can are 3 alleles (A, B, and O) that contribute to blood types in humans. Each person can have only two versions of the trait in their genome at one time, but in the population there are 3 forms. In fruit flies, there are many different versions of eye color in the population, but one fly can have only 2 alleles at a time. Polygenic traits are those where more than one GENE contributes to the phenotype. For example, the current model of skin color is that there are 3 genes that contribute to skin color. So there are 6 total alleles, 3 from the mother and 3 from the father. Multiple alleles=more than two forms of the same gene in the population Polygenic traits=more than one gene contributes to the phenotype

vanhoeck



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