Codominance | Genetics | Biology | FuseSchool

Codominance | Genetics | Biology | FuseSchool

In this video we are now going to look at codominance.

You need to understand the difference between genotype and phenotype. The genotype is the set of genes. The phenotype are the physical characteristics that are coded for by the genotype.

A monohybrid cross is the study of the inheritance of one characteristic - such as the pea-pod colour. They will either be green or yellow. Not a mixture of the two. Only one of the alleles is expressed, and the yellow allele is dominant so in the Yy genotype the yellow pod colour wins.

In codominance, the alleles are both expressed in the same phenotype - so you can end up with a mixture. Neither allele is dominant.

This happens with chickens. Neither the black nor the white allele is dominant, so the BW genotype gives a speckled phenotype.

Codominance is seen throughout the animal and plant kingdoms. It is also seen in our blood groups.

There are 4 blood groups; A, B, AB and O. There are 3 different possible alleles for blood group: IA IB IO. But we each only have two of them - one from our mother and one from our father. IA and IB are codominant. Io is recessive to both IA and IB. IA and IB are codominant. Io is recessive to both IA and IB These genotypes give these phenotypes. If you inherit IA from your mother and IB from your father, you will be AB blood group. To be blood group O, both of your parents must have at least one Io allele. Your parents could be either of these 3 genotypes: IAIO, IBIO or IOIO.



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