Bio Question

[riro2]

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Hi there,

Considering a diploid organism, can a single chromosomal strand ever have both alleles of a particular gene on it?

 

[Ibraiz]

Alleles are on sister chromatids at the same locus (location). I have never heard of same alleles to be found on the same chromatid.

 

[Troyvdg]

Hi there,

Considering a diploid organism, can a single chromosomal strand ever have both alleles of a particular gene on it?

I think a duplication during crossing over could produce two of the same alleles on a single chromosome, but for a diploid organism you would still have two homologous chromosomes

 

[Ibraiz]

I am not 100 % on this one but I was under the impression crossing over is exchange of genes between two non-sister chromatids. I never heard of duplication of gene/allele during crossing over. I am not challenging your answer but I am verifying my knowledge.

 

[Dor17]

what about translocation?

 

[Ibraiz]

"In genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes"

http://en.wikipedia.org/wiki/Chromosomal_translocation

Nonhomologous chromosomes don't have allele for the same gene

 

[RCT PC CRN]

I think a duplication during crossing over could produce two of the same alleles on a single chromosome,

I doubt this cause crossing over happens at same locus on non-sister chromatids (tetrad, between homologous chromosomes) so it will flip the allele. I don't see the way to join them together on same chromatide.

Unless transduction (translocation) happens so the locus will be changed for one of the allele and now crossing over happen. Not sure about the possibility and existence of later scenario.

I think the only way to get a two copies of same allele is the nondisjuction.