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Regina Bailey

What Are Alleles?

By May 15, 2010

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Credit: Steve Berg

An allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome. These DNA codings determine distinct traits that can be passed on from parents to offspring. The process by which alleles are transmitted was discovered by Gregor Mendel and formulated in what is known as Mendel's law of segregation.

Mendel studied various characteristics of pea plants, one of which was seed color. The gene for seed color in pea plants exists in two forms. There is one form or allele for yellow seed color (Y) and another for green seed color (y). One allele is dominant and the other is recessive. In this example, the allele for yellow seed color is dominant and the allele for green seed color is recessive. Since organisms have two alleles for each trait, when the alleles of a pair are heterozygous, the dominant allele trait is expressed and the recessive allele trait is masked. Seeds with the genetic makeup of (YY) or (Yy) are yellow, while seeds that are (yy) are green.

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Comments

November 29, 2011 at 10:27 pm
(1) LoL says:

LOL man,

your definition is too hard!

September 2, 2012 at 1:52 pm
(2) Tehhee says:

Thnx for the def. but it’s too long
>:/

January 13, 2013 at 9:07 am
(3) imelda g. says:

d def is splendid bt cn u mke it a summary

September 10, 2013 at 5:05 pm
(4) Cm says:

Good thanks

November 30, 2013 at 11:43 pm
(5) munira says:

Still dint get it :S

December 6, 2013 at 9:50 pm
(6) Anon says:

The first line is the definition of an allele.
Say there are two options for a characteristic, coded for by the genes (Y) and (y) (they determine the characteristic). (Y) and (y) are alleles – alternative forms of the same gene that code for different characteristics. In her example (Y) codes for yellow seeds and (y) codes for green seeds.

March 2, 2014 at 12:40 am
(7) debapriya says:

Thank u soooo very much

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