Genetics as it applies to evolution, molecular biology, and medical aspects.
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The other is fully inactive. The product of only one allele - dominant allele - is functional.
For example, deletion of a locus on one of two homologeous chromosomes will make the second allele fully dominant ( if it's homosufficient ).
Say, A codes for RED eyes, a codes for BLUE eyes. A heterozygote, A/a will produce red-blue color of eyes .
Now if deletion of a occurs than A's product will be only pigment which will paint eyes in red, without blue pigment interference.
Last edited by druid on Wed Nov 01, 2006 2:03 am, edited 1 time in total.
so the recessive allele is inherently inactive... if so what will be the case with two recessives or like the case u mentioned. if it is inactive how can it be used to code for a protein.
Also can you please explain what homosufficient is. Thanks a lot.
With two recessives no protein will be produced. So no pigment - neither red nor blue will be produced at all and eyes` color will be let me assume transparent
Homosufficient is when product of only one allele is sufficient for phenotipic trait to appear. Well, the example doesn't require usage of this term.
Moreover, even heterozygote may die. Suppose A/A produce enzyme E. Heterozygote A/a will produce only half of amount of E in homozygote A/A. If half of amount of enzyme E is insufficient for living, we'll soon go to funeral of heterozygote. That's a case when allele A homoINsufficient.
I thought that if there were 2 recessives then the color of the eyes will be blue....... so how can we can get transparent eyes?
Thanks for your help
"Say, A codes for RED eyes, a codes for BLUE eyes. A heterozygote, A/a will produce red-blue color of eyes.
Now if deletion of a occurs then A's product will be only pigment which will paint eyes in red, without blue pigment interference."
I hope you agree with that.
Now suppose there occured two deletions - of A allele and of a allele. Do you agree with me that NO genes produce NO their products? Therefore by no means eyes can be blue, because a was deleted and cannot produce protein which gives eyes blue color. The same is about A allele. So what do we get? We get no pigments that can paint eyes. What color can eyes be if there's no pigment that can paint them? But you are right - they will not be transparent ( note, i gave smile ) because there is one billion things in eye that prevent it from being transparent
hmm... ok i think i understand the explanation. so u are saying that the recessive allele is deleted from its locus, if there is a dominant allele in the cell. is that even possible; if not is there something like a marker that infront of the gene that tells a cell that it is the dominant one.
There are many ways by which one allele can be made recessive relative to other. It has not to be obligately deletion. For example, gene A produces pigment for RED color, allele a produces pigment for BLUE color. Suppose RED pigment can catalize degradation of BLUE pigment. Then blue color of eyes can appear only in homozygous a/a. Why not in heterozygous? A will produce pigment for red color AND a will produce pigment but for blue color. Because red pigment will degrade blue pigment (AFTER both have been synthesyzed ) phenotype will be RED. Here dominance of A is determined NOT by deletion of homologeous allele but by dominance of PRODUCT of A over PRODUCT of a.
No, there is not such a marker. It's like in sport - you are not born with champion medal, you must PROOVE your dominance in struggle.
11 posts • Page 1 of 1
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