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describe how you could use genetic crosses to distinguish between co-dominance v

ID: 165533 • Letter: D

Question

describe how you could use genetic crosses to distinguish between co-dominance vs. dose effect.

Incomplete dominance (dose effect) or co-dominance ? In class we discussed that in some cases it can be difficult to distinguish between co-dominance and incomplete dominance using genetic crosses. Our discussion in class referred to a diploid species where flower color was coded by a single locus where AA=red, aa=white and Aa=pink (see slide below). The pink color could be caused by only a half of red pigment in heterozygotes (dose effect), or because the presence of red and white pigment gives pink (co-dominance). Things would get much easier if, instead of a diploid plant, we where using a tetraploid plant. In that case. AAAA=red. aaaa=whitc, AAaa=pink. In 200 words or fewer, describe how you could use genetic crosses to distinguish between co-dominance vs. dose effect. In the case of co-dominance, assume that the amount of pigment produced by an allele is independent from the number of alleles present. The best 5 submissions get an extra 5 points.

Explanation / Answer

answer :lncomplete dominance:

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lncomplete dominance:

Since there are only 2 alleles & three phenotypes (red ,pink white)

The flowers of the plant can be---- red, pink, or white.

AA =RED ;  

Aa=pink

and aa=WHITE

Colour is determined at a single locus.

The genotype AA--------- results in red flowers

and aa ----------results in white flowers

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Aa=pink       --------- an intermediate phenotype in Fl but parental phenotypes reappear in F2.

Aa pink       x    Aa pink

A

a

A

AA =RED

Aa pink

a

Aa pink

aa=WHITE

this depicts that heterozygote--different from homozygotes-------lack of complete dominance .

intermediate phenotype : --------when compared to the homozygous dominant or homozygous recessive individuals,

this is said to be known as incomplete dominance.

A

a

A

AA =RED

Aa pink

a

Aa pink

aa=WHITE