The inhabitants of the planet Mendel have three alleles for hair color: red (R), white (W) and blue (b). The R and W alleles exhibit codominance, and individuals with an RW genotype have pink hair. The b allele is recessive, so only individuals with a bb genotype have blue hair. If a red-haired Mendelian mates with a white-haired Mendelian, what are all the possible hair color phenotypes their offspring might theoretically have

4 RW pink hair color

Explanation:

Let the allele for red hair color = R

Let the allele for white hair color = W

Let the allele for blue hair color = b

Since R and W exhibit co dominance it means none of both traits have the tendency or capability to masked the other .

As such individual with RW genotype = PInk hair color

Allele b is recessive and only individuals with the genotype bb exhibit the blue allele  

Now; if a cross occurs between a red-haired Mendelian and a white-haired Mendelian

i.e

RR   × WW

we have

           R           R

W         RW       RW

W        RW         RW

So we have the following offspring :

4 RW = 4 pink

So theoretically , the possible phenotypes results to 4 RW pink hair color

All of them will have pink hair,that is RW

When a homozygous red hair (RR) is crossed with a homozygous white hair (WW), all the offsprings will have pink hair(RW).

This is because self y pollination of the pink hair F1 generation offsprings produces a mixture of F2 generation offsprings bearing red(RR), pink(RW) and white (WW) in the ratio of 1:2:1.

This reappearance of the red hair and white hair offsprings in the F2 generation shows that the alleles (R) and (W) have remained unaltered in the F1 generation.

All the offsprings will have a phenotypic pink hair because the (R) and (W) are not dominant over each other.

The effect of each allele is modified by the presence of the other to produce a third phenotype (the pink hair offspring). This is known as incomplete dominance. Here, the way the alleles for hair are segregated and transmitted agrees with Mendel's proposals.

The observed phenotypic ratio of 1:2:1 in the F2 generation instead of the typical Mendelian 3:1 ratio is due to the hetero zygote showing a hair colour of its own.

Incomplete dominance is the ability of two alleles to produce a heterozygous phenotype that is different from the two homozygous phenotypes

that is wrong, its not thymus.

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