CODOMINANCE
When both alleles of a pair are fully expressed in f1 hybrids,they are called co-dominants and this phenomenon is called co-dominance.the example of co-dominance are :
1.roan colour coat of cattle
2.abo- blood group of human
In case of blood groups in human, both A and B genes produce an effect in a heterozygous individual. The genes which gives A and B blood groups are alleles. Each control the formation of a different red blood cell antigen. Antigen a in case of person having blood group A and antigen b in individuals with blood group B. . The heterozygous individuals with blood group AB contains both antigen a and b. Both proteins are detected in equal amounts in the red cells.
A mating between A-type AA and a homozygous B-type BB would result in all heterozygous offsprings AB. selfing AB would result in ratio 1:2:1(AA:AB:BB),which replaces phenotypic ratio 3:1 because alleles are codominant.
Genetic diagram:
INCOMPLETE DOMINANCE
When both the alleles show their expression and the hybrids appear intermediate between two parents,then it is called incomplete dominance.
This was first observed by correns in 4o'clock plant mirabilis jalpa. A cross between a pure red flower (RR) and a pure white flower(rr) of 4o' clock plant produces hybrid pink flowered plants in f1 generation,a character which is ntermediate between both.
Genetic diagram :
This cases suggest that the dominance is not universal or absolute.
When both alleles of a pair are fully expressed in f1 hybrids,they are called co-dominants and this phenomenon is called co-dominance.the example of co-dominance are :
1.roan colour coat of cattle
2.abo- blood group of human
In case of blood groups in human, both A and B genes produce an effect in a heterozygous individual. The genes which gives A and B blood groups are alleles. Each control the formation of a different red blood cell antigen. Antigen a in case of person having blood group A and antigen b in individuals with blood group B. . The heterozygous individuals with blood group AB contains both antigen a and b. Both proteins are detected in equal amounts in the red cells.
A mating between A-type AA and a homozygous B-type BB would result in all heterozygous offsprings AB. selfing AB would result in ratio 1:2:1(AA:AB:BB),which replaces phenotypic ratio 3:1 because alleles are codominant.
Genetic diagram:
INCOMPLETE DOMINANCE
When both the alleles show their expression and the hybrids appear intermediate between two parents,then it is called incomplete dominance.
This was first observed by correns in 4o'clock plant mirabilis jalpa. A cross between a pure red flower (RR) and a pure white flower(rr) of 4o' clock plant produces hybrid pink flowered plants in f1 generation,a character which is ntermediate between both.
Genetic diagram :
This cases suggest that the dominance is not universal or absolute.
what is over dominance?
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