A gene showing codominance has :
alleles tightly linked on the same chromosome
alleles that are recessive to each other
both alleles independently expressed in the hetero zygote
one allele dominant on the other
As learnt in
Co-dominance explained in red-blood cells -
Red-blood cells are controlled by gene (I). RBC's have sugar attached to surface which is controlled by the gene (I). The gene (I) has three alleles : IA , IB and
- wherein
The allele of gene (I), IA and IB process sugar of different forms while does not produce any.
A gene shows codominance when both alleles in heterozygous condition, express their traits independently instead of showing dominant-recessive relationship and such alleles are called codominant alleles.
Option 1)
alleles tightly linked on the same chromosome
This option is incorrect.
Option 2)
alleles that are recessive to each other
This option is incorrect.
Option 3)
both alleles independently expressed in the hetero zygote
This option is correct.
Option 4)
one allele dominant on the other
This option is incorrect.