I need a good perception on what an allele is.?

Question

im new to this, which sucks because i have so many question and im going to run out of points... aside from the point. I dont really want a 'definition" so to say although i would appreciate the gesture, i have looked it up an am still confused.

I just don't really understand the concept of what an allele is. thanx

Answer 1

DIFFERENT and SAME. These two words are the key to gaining a concept of what an allele is. Alleles are different forms of the same gene. Since a gene controls a specific trait, different forms of the gene give different characteristics of the same trait. Take eye color, for example. There is a gene which controls what eye color you have. But one allele, or form of the gene, may give you brown eyes whereas another allele, a different form of the same gene, may give you blue eyes. Yet another allele could give you hazel, or green or whatever. Most of the DNA in a gene will give it instructions to control a certain trait (in this case, most of the DNA in the gene for eye color dictates that it will, in fact, control EYE COLOR and not some other trait). However, a small portion of the DNA in that gene is highly variable in a population, with the variety accounting for the differences in the trait itself. The differences here account for the different phenotypic expressions: blue eyes, brown eyes, etc., as above.

For every trait you have two alleles (there may be 20 alleles for a trait, but you can only have two of them--one you get from your mom, the other you get from your dad). If both of the alleles are the same, you are said to be homozygous. If both are different you are said to be heterozygous. A dominant allele controls what you actually look like, or the phenotype of the trait. A recessive allele is one that can not be seen in what you look like (if a dominant allele is present). Take height of a pea plant for example. There is a gene that controls height. The dominant allele is T, which produces a tall plant. The recessive allele is t, which produces a short plant. Each offspring will receive TWO alleles, so the possible combinations are TT, Tt, and tt. Both TT and tt are homozygous, since both the alleles for the trait of height are the SAME. However, Tt is a heterozygous plant, since both alleles for the trait are different. All is takes is one dominant allele present to control the phenotype, or the outward expression of the trait. TT will therefore produce a tall plant. Tt will also produce a tall plant, because the dominant allele, T, controls the phenotye. Only tt will produce a short plant.

In summary, alleles are different forms of the same gene. A gene controls a trait, and therefore alleles give different appearances for the same trait. I hope this helps you. Good luck!

Answer 2

Gene's often have 2 alleles. This means, that there are 2 versions of the same gene. One allele is inherited from each parent.

Usually, one allele is said to be dominant over the other. eg AA (which is homozygous because the 2 alleles are both A). This means that whatever that allele codes for will be expressed.

A recessive allele eg aa (also homozygous) will only usually be expressed if there are 2 recessive alleles like aa. This is because the A will always dominate over the a. Kinda like a tall skinny person always winning the race before the shorter, unfit person gets halfway there.

Aa = heterozygous. The 2 alleles are different, but because of the presence of the A, the phenotype (the gene expression you see, eg hair colour) will be determined by the A.

Hope this helps a little

Answer 3

Hi. Try this link : http://www.answers.com/main/ntquery?s=allele&gwp=16 That is just a definition, hold on. The allele is a gene pair. They can be the same or different. Mendel doing his pea plant research was able to affect the plants characteristics and, although he did not know it, he was manipulating the gene pairs. Genetics has a long way to go to FULLY understand at the DNA level what goes on, but at the gene level they have a pretty good idea. I hope this is OK.

Answer 4

In Mendelian genetics, an allele is one of a pair of genes that dictate a specific trait (phenotype). The term allele is used in reference to genes that occupy a specific locus on a given chromosome. All that really means is that we use the term allele when we refer to varient form of a gene. So a gene will control the color of a flower's petals. One allele will determine that color to be red. Another allele will determine that the color is white. One gene with variants. Those variants are the allele.

Answer 5

O.K...each gene is made up of two alleles. For example, if you take the gene that determines seed shape in Pea plant...R=Round shape and r=Wrinkled shape. If the gene is made up of RR or Rr the pea will be round, because R or round is dominant. If the gene is made up of rr, then the pea will be wrinkled. Basically, an allele is just the name given to the two codes that make up a gene and determine that genes characteristic.

Answer 6

In school eye colour is taught as a single gene trait - in reality it is much more complex than that. Over 15 genes have been identified so far, several of which are very variable in some populations. Most parents have the potential to have children with any colour eyes. Blue is probably unlikely in your family, unless you have grandparents or great grandparents on your maternal side with eye colour other than brown, but it is not impossible.