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Gene's and Allele's when to use each?

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Gene's and Allele's when to use each?

Postby taylorgrace » Sun Oct 25, 2009 2:18 am

What is the difference between a Gene and an Allele?
when i'm answering questions i always get confused on whether to write allele or gene. help.
:?:
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Postby kolean » Sun Oct 25, 2009 4:10 am

http://www.merriam-webster.com/dictionary/allele

An allele (pronounced /ˈæliːl/ (UK), /əˈliːl/ (US); from the Greek αλληλος allelos, meaning other) is one of a series of different forms of a gene. The word is a short form of allelomorph ('other form'), which was used in the early days of genetics to describe variant forms of a gene detected as different phenotypes. Alleles are now understood to be alternative DNA sequences at the same physical gene locus, which may or may not result in different phenotypic traits. In any particular diploid organism, with two copies of each chromosome, the genotype for each gene comprises the pair of alleles present at that locus, which are the same in homozygotes and different in heterozygotes. A population or species of organisms typically includes multiple alleles at each locus among various individuals. Allelic variation at a locus is measurable as the number of alleles (polymorphism) present, or the proportion of heterozygotes (heterozygosity) in the population.

For example, at the gene locus for ABO blood type proteins in humans[2], classical genetics recognizes three alleles, IA, IB, and IO, that determines compatibility of blood transfusions. Any individual has one of six possible genotypes (AA, AO, BB, BO, AB, and OO) that produce one of four possible phenotypes: "A" (produced by AA homozygous and AO heterozygous genotypes), "B" (produced by BB homozygous and BO heterozygous genotypes), "AB" heterozygotes, and "O" homozygotes.[1]
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Postby Darby » Mon Oct 26, 2009 8:52 pm

Think of a gene as a basic food type, and an allele as a particular recipe for that food.

You'd have a gene for chocolate-chip cookies, and many alleles for all of the different chocolate-chip cookie recipes.
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Postby kolean » Tue Oct 27, 2009 2:24 pm

Maybe a more basic analogy would be apples.
An 'apple' is the gene. The allele would be a yellow apple (Golden Delicious), a red apple (Red Delicious), and a green apple (Granny Smith).
So genotypically the allele is yellow, red, or green (is there any other basic colors for apples?) for the gene 'apple'. And in a diploid organism, there would be 2 alleles per gene.
Now, phenotypically there can be all sorts of expressions: green with red spots, yellow with red spots, red with yellow spots, etc.
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Re:

Postby qqsvery » Mon Nov 02, 2009 6:37 am

kolean wrote:Maybe a more basic analogy would be apples.
An 'apple' is the gene. The allele would be a yellow apple (Golden Delicious), a red apple (Red Delicious), and a green apple (Granny Smith).
So genotypically the allele is yellow, red, or green (is there any other basic colors for apples?) for the gene 'apple'. And in a diploid organism, there would be 2 alleles per gene.
Now, phenotypically there can be all sorts of expressions: green with red spots, yellow with red spots, red with yellow spots, etc.

You compare gene as Apple,I think you just mean the phenotype,gene is a DNA sequence of a phenotype,and allele is just another alternative gene(DNA sequence) which show the different phenotype.
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Re: Re:

Postby JackBean » Mon Nov 02, 2009 8:50 am

qqsvery wrote:gene is a DNA sequence of a phenotype,and allele is just another alternative gene(DNA sequence) which show the different phenotype.

No, gene is a part of DNA, let's say nucleotides 1120-2310 in E.coli genome, no matter, what is in there. Alleles are the variants, which can occur in there.
Allele is NO alternative gene
Last edited by canalon on Mon Nov 02, 2009 10:09 pm, edited 1 time in total.
Reason: Fixing quote
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Re: Re:

Postby qqsvery » Tue Nov 03, 2009 2:30 am

JackBean wrote:
qqsvery wrote:gene is a DNA sequence of a phenotype,and allele is just another alternative gene(DNA sequence) which show the different phenotype.

No, gene is a part of DNA, let's say nucleotides 1120-2310 in E.coli genome, no matter, what is in there. Alleles are the variants, which can occur in there.
Allele is NO alternative gene

Of course I know gene is a part of DNA,I did say it ,right?Allele is an selective gene sequence when recombination occurs!
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Re: Gene's and Allele's when to use each?

Postby JackBean » Tue Nov 03, 2009 7:40 am

No, you said, that
allele is just another alternative gene
and that's not true. Gene is just a piece of DNA, allele says you, what does this piece look like (what is its sequence)
http://www.biolib.cz/en/main/

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Re: Gene's and Allele's when to use each?

Postby qqsvery » Mon Nov 09, 2009 6:02 am

JackBean wrote:No, you said, that
allele is just another alternative gene
and that's not true. Gene is just a piece of DNA, allele says you, what does this piece look like (what is its sequence)



You are completely wrong! 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.

Organisms have two alleles for each trait. When the alleles of a pair are heterozygous, one is dominant and the other is recessive. The dominant allele is expressed and the recessive allele is masked.

You can learn more on this website:http://biology.about.com/od/geneticsglossary/g/alleles.htm
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Postby JackBean » Mon Nov 09, 2009 6:41 am

1) how I understand your post is: one version of it is gene, if it is an another version, than it is an allele
That's not true. It is always allele and it is always a gene. But gene is like AHK4, what is histidine kinase from Arabidopsis. This gene has several versions, the wild-type - AHK4 and several mutants like wooden leg etc. All of them, including the WT version are alleles.
2) the alleles doesn't have to be one dominants and second recessive, they can be codominant etc.
3) the recessive allele can be expressed (and is) also, just it doesn't work, as it should...
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