Monohybrid crosses with incomplete dominance and codominance

Monohybrid crosses with incomplete dominance and co-dominance The red and white alleles for the snapdragon flower color gene exhibit incomplete dominance. When pink flowers were produced from red- and white-flowered parents, early geneticists thought this might represent \"blending inheritance, \" where the hereditary information from one parent melded with the information from the other. Use Punnett Squares to determine the phenotype ratios in snapdragon offspring from the following crosses, that show that blending inheritance is not an accurate way to characterize this situation. define the notation (letters) you will use: pink x pink (if blending inheritance were accurate, we would predict that all offspring would be pink) pink x red (if blending inheritance were accurate, we would predict that all offspring would be dark pink)

Solution

A cross between pink and pink flower plants.

The genotype of pink flower plants would be Rr (R allele for red colour and r allele for white colour). A case of incomplete dominance.

The gamete formation results in R and r genotypes

And the offsprings will be red ,pink, white in the ratio of 1:2:1 respectively.

All offsprings are not pink. There is segregation of alleles during gamete formation, that results in new combination of genes in tha offsprings. Here alleles for red and white colour were present in the parents and their offsprings also contains new combination of alleles.

A cross between red and pink flower plants.

The genotype red is RR and pink is Rr. The cross between the two results in red and pink flowere in equal ratio 2:2.

Here the alleles were present for red and white colour in the parents RR X Rr.

There is no occurance of blending inheritance, Here the concerned genes for red (RR) and white (rr) colour show incompletee dominance when come together in an organism and shows pink colour (Rr). This does not mean that it happens in all conditions, as the conditions are exceptional cases. Here the heterozygote (Rr) posses genes for both red and white colour and when self crossed results in new combination of genes due to their segregation during gamete formation and homozygous condition will be retained in some plants (RR and rr) that results in red and white flowers.

	R	r
R	RR	Rr
r	Rr	rr