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Author Topic: Why are there multiple alleles for each gene?  (Read 7362 times)

Offline LukyTom

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Why are there multiple alleles for each gene?
« on: 10/07/2010 13:41:17 »
I was always taught that a gene is a sequence of DNA which codes for a polypeptide bond. What I dont understand is how in each gene there are two alleles.

From the polypeptide production phase, more specifically the transcription phase of polypeptide synthesis, one strand of the double stranded DNA molecule will eventually code for one polypeptide. Hence I am assuming that the other strand (complementary) codes for the recessive allele (is this where i am mistaken?) Hence by this logic, the homologous chromosome, would also contain a pair of these alleles. Hence each body contains 4 pairs of alleles. ???

Can some please explain?

Also, just curious about the mechanism of selecting the recessive and dominant alleles for phenotype expression. Thanks.
« Last Edit: 24/03/2011 21:09:14 by chris »


 

Offline tangoblue

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Re: Why are there multiple alleles for each gene?
« Reply #1 on: 26/10/2010 23:41:17 »
This is the stuff that i get confused with too!
 

SteveFish

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Re: Why are there multiple alleles for each gene?
« Reply #2 on: 27/10/2010 03:53:56 »
An allele is a variant for a specific gene. For each individual there can be one or two alleles for each gene, one from each parent. If both parents provided the same allele to an offspring, this individual will be homozygous for this allele. If an individual inherits two different alleles, they will be heterozygous for the trait. However, a population may have one, two, or many different alleles for a specific gene which could result in one to many different individuals for the trait coded by the gene.
 

Offline Jessica H

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Re: Why are there multiple alleles for each gene?
« Reply #3 on: 31/10/2010 02:59:31 »
There is only one "sense" strand on the chromosome.  The other strand is not the other allele, it is the sequence of letters that is the complete opposite of the actual gene, basically "nonsense".  The other allele is on the homologous chromosome, as you've said.  It might vary by just one or two letters from the other allele.
 

Offline tangoblue

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Re: Why are there multiple alleles for each gene?
« Reply #4 on: 01/11/2010 00:59:09 »
This is probably a really stupid q, but is an allele just dna
 

SteveFish

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Re: Why are there multiple alleles for each gene?
« Reply #5 on: 01/11/2010 01:53:03 »
Tangoblue:

Yes. DNA is a large collection of genes and alleles are different versions of individual genes.

Steve
 

Offline tangoblue

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Re: Why are there multiple alleles for each gene?
« Reply #6 on: 03/11/2010 20:19:06 »
So, how many genes are in a strand of dna and how many helix' are in a chromatid
 

Offline Lemonpie

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Re: Why are there multiple alleles for each gene?
« Reply #7 on: 16/03/2011 18:51:15 »
Sorry, Can't find a place to ask this, but is there a gene for colour differentiation?
 

The Naked Scientists Forum

Re: Why are there multiple alleles for each gene?
« Reply #7 on: 16/03/2011 18:51:15 »

 

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