Question

Explain why the ABO blood types are an example of codominance? Be sure to briefly define codominance in your answer.

Answer 1

Answer-

According to the given question-

Co- dominance- Allele are the genes that are present on a  chromosome alternatively. alleles generally present on a chromosome occurs as pairs or more than two alleles are also present  and express a particular trait or phenotype when both the allele are same the genotype is called homozygous and if the alleles are different for a particular phenotype or traits then this genotype is celled heterozygous. when a allele override on the other allele for a particular trait then this is called dominant otherwise called recessive. but in some cases the neither allele override on other allele or cannot mask the expression but act equally are called co- dominance. it is a type of heterozygous  condition where two alleles present on a loci of gene are completely expressed for a particular trait or phenotype.

for e.g. in case of human blood group ABO , the gene I control three alleles namely alleles A, alleles B, and alleles O. here allele A and allele B are codominant while allele O is recessive.

Blood type	Genotype
A	IAIO AO IAIA AA
B	IBIO BO IBIB BB
AB	IAIB AB
O	IOIO OO

ABO Blood Type	Antigen A	Antigen B	Antibody anti-A	Antibody Anti-B
A	yes	no	no	yes
B	no	yes	yes	no
O	no	no	yes	yes
AB	yes	yes	no	no

Parent Allele	A	B	O
A	AA (Blood group A)	AB (Blood group AB)	AO (Blood group A)
B	AB (Blood group AB)	BB (Blood group B)	BO (Blood group B)
O	AO (Blood group A)	BO (Blood group B)	OO (Blood group O)

here both allele A and allele B are dominant over allele O, due to which the human having genotype AO  will show A phenotype and human with genotype BO will show B phenotype and those have genotype OO will show O phenotype. and both the allele A and allele B are showing co-dominance here.