Incomplete Dominance

[genuresilience]

Does anyone know how incomplete dominance works in inheritance and what traits does it usually effect?

[DeanK2]

Not entirely sure that the question would contain the words incomplete dominance as it does not exist. The actual term is co-dominance - extremely important this is used, as in a question; the use of incomplete would loose all marks. Co-dominance is the term used to describe the way two DIFFERENT alleles are expressed in the phenotype of an organism.

 

Consider these crosses in a punnet square:

R-dominant, r – recessive

R produces white flowers. r results in blue flowers

r R

R Rr RR

r rr Rr

It is clear that the genotype with a capital R would have white flowers. Approximately 3:1 would have white: blue flowers.

 

The punnet tables are not easy to show, but top row of each one should be moved over by a place.

 

 

Now, in co-dominance, there is actually no dominance. Both alleles are equally expressed:

 

r R

R Rr RR

r rr Rr

 

So, RR would be white, and rr would be blue. Rr would be a light blue - because neither allele is dominant over the other, the heterozygous genotype has its own phenotype. However, since the original phenotype has been unaltered and remains, they still obey Mendel's law of segregation. It is only the phenotype that appears to have undergone "incomplete dominance", and this is a common mistake.

 

Co-dominance affects blood groups - that is why the AB group can be present - the A or B allele is not dominant, so both antigens are produced.

[genuresilience]

Thanks for that, it makes sense

[asaroj27]

Mendel's law of dominance is different from law of purity.And you are talking about law of dominance as well as law of purity simultaneously.Hetrozygous always have two different alleles. In F2 generation on self pollination genotypicaly they segregate acording to the 1:2:1.that is law of segregation.

[asaroj27]

hello

if red flower crosses with white flower it is expected that red flower comes in F1 generation because red is dominant over white according to mendel's law. But in case of 4 o' clock (plant name) pink colour flower comes in place of red because of incomplete dominance of red over white. it comes but not fully.