Codominance and Multiple Alleles

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  • Created by: Hannah
  • Created on: 10-11-12 17:25

Co-dominance and Multiple Alleles

Co-dominance is shown by 2 alleles that are neither dominant or recessive. In the heterozygous condition, they produce a phenotype that is different from the homozygous state of either allele.

As neither allele is dominent, the different alleles are represented by a different upper case letter for each allele. e.g. R (for ared flower) W (for a…

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Jessi Parker

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Hey, I'm doing A2 human biology. I kind of understand the concept of co-dominance, meaning that too dominant allele are expressed through the phenotype. However, I do not understand the second sentence of your explanation, I have a similar sentence in by HBIO booklet which I do not understand either...

"In the heterozygous condition, they produce a phenotype that is different from the homozygous state of either allele."

Could you please help me out and help me understand what it means???

Thank you,

Jessie :)

ellridd

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Homozygous state = the organism is diploid comprised of 2 of the SAME alleles.

Heterozygous is when the 2 alleles are different...

EXAMPLE:  We have 2 alleles :

  1. allele for RED pigmentation ( homozygous state = red petals)
  2. and the allele for WHITE pigmentation (homozygous state = white petals)

These 2 alleles are co dominant, SO when put together, they are equally dominant. And when they are put together the genotype is HETEROZYGOUS as there is one allele for red and one allele for white...this 'mixes' the 2 alleles so in the heterozygous state the petals are PINK. (red+white = weakened red / pink).

Hope this helps people :) 

Ell

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