Codominance and Incomplete Dominance

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AlyHawthorne
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Codominance and Incomplete Dominance

Post by AlyHawthorne » Wed Mar 15, 2006 2:53 am

Hi guys! Quick question.

I ran across a post covering this earlier, but I'm still slightly confused (sorry).

Are codominance and incomplete dominance the same thing? Or even slightly the same? I thought that codominance was red x white flowers = red, white, and pink flowers, while incomplete dominance was red x white flowers = only pink flowers. Is that correct?

If so, I have another question. We're doing a lab right now on dominant/recessive traits. Would hair that has the phenotypes of (homozygous dominant), wavy (heterozygous), and straight (homozygous recessive) be incomplete dominance? Or would it be kinda-sorta codominance? Is it arguable for either?

Sorry - that turned out to be more than a quick question.

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Khaiy
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Post by Khaiy » Wed Mar 15, 2006 3:22 am

It's not quite right. Codominance/incomplete dominance are a description of an allele. You can't figure out what the phenotypic results of a cross would be unless you saw the parentals first. Example: If R is an allele for red, and r is an allele for white, and it's an incomplete dominance trait, the a red allele plus a white allele (Rr) would be pink. But if you had RR, then even though the trait exhibits incomplete dominance the only allele present is red.

What phenotype did you say it was for homozygous dominant? Is it that the problem you have to solve? If homozygous dominant has a wavy phenotype, then it's a complete dominance trait. If you don't know what the homozygous phenotype is, then it's unknown whether the trait exhibits complete dominance or not. Do you see why from the explanation I wrote above? If not, I can probably explain it better.

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MrMistery
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Post by MrMistery » Wed Mar 15, 2006 7:27 pm

About hair it is like this(considering the alleles H and H):
HH: curly
Hh: wavy
hh: straight
It is a case of incomplete dominance, because the heterozygous individuals have a phenotype that is in between the pheotypes of the homozygous recessive and the homozygous dominant individuals.

Now, let me exaplin codominance and incomplete dominance. In both of them, the heterozygous individual has a different phenotype than the homozygous individuals. In incomplete dominance,you can take the example of the white and red flower causing the apperance of the pink flower. But if the relation between the 2 genes would have been codominance and not incomplete dominance, the resulting flower would have been something like a flower that had a lot of red and white dots on it - both pheotypes express...

Hope it is more clear now...
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AlyHawthorne
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Post by AlyHawthorne » Thu Mar 16, 2006 2:15 am

Ah, alright. Thanks for all the help!

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