Question

In the ABO blood group inheritance, the A and B alleles are codominant, and O is recessive to both the A and B alleles. if a man with type B blood and a woman with type A blood Marry, the phenotype of their children could be
A)A only
B)B only
C)AB only
D)A, B, or AB
E)A, B, AB, or O

Answer 1

The blood groups of humans are determined by the codominant alleles. Mainly there are three different types of alleles presently known as ${ I }^{ A }$, ${ I }^{ B }$, and i. The ${ I }^{ A }$ and ${ I }^{ B }$ alleles are codominant whereas the i allele is recessive. So, the possible phenotypes for the blood group are type A, type B, type AB, and type O.

Complete answer:
-The individuals with type a and type b can be either homozygous (${ I }^{ A }{ I }^{ A }$ ) or heterozygous(${ I }^{ A }i$ or ${ I }^{ B }i$ ).
-Man has (IBIB and IBi) genotypes with B blood group while women have (IAIA and IAi) genotypes with A blood group. The presence of all three alleles in the couple allows them to have children with all the four possible phenotypes.
-The four different genetic crosses are possible. All four crosses must be computed to determine all possible although one cross (${ I }^{ A }i$ mother $x{ I }^{ B }i$ father) is the most revealing.

Mother (Type A)	Father (Type B)
${ I }^{ A }{ I }^{ A }$	${ I }^{ B }i$
${ I }^{ A }{ I }^{ A }$	${ I }^{ B }{ I }^{ B }$
${ I }^{ A }i$	${ I }^{ B }{ I }^{ B }$
${ I }^{ A }i$	${ I }^{ B }i$

Additional Information: -The blood type of a human is determined by the codominant Alleles.an allele carries different types of genetic information that is present in DNA at a specific location on a specific chromosome. Mainly there are three different alleles for human blood type which is known as ${ I }^{ A }$, ${ I }^{ B }$, and i. For clarity, we can call these alleles A (for ${ I }^{ A }$ ), B (for ${ I }^{ B }$ ), and O (for i).
-We inherit allele one from our biological mother and one from our biological father. So every one of us has ABO blood type allele. The information present on the pair of alleles in DNA is called the genotype. -Generally, there are three different alleles. So, a total of six different genotypes at the human genetic locus is present. The different types of genotypes that are possible are AA, AO, BB, BO, AB, and OO.
-Codominance is a phenomenon in genetics, in which two alleles are exhibited to an equal degree within an organism. As a result, traits related to each allele are displayed at once.

Note: The comparison between phenotype i.e blood type and genotype is demonstrated in the table. The mother with blood type A and father with blood type B could be either homozygous or heterozygous.

Phenotype (Blood type)	Genotype
Type A	${ I }^{ A }{ I }^{ A }$ or${ I }^{ A }i$
Type B	${ I }^{ B }{ I }^{ B }$ or${ I }^{ B }i$
Type AB	${ I }^{ A }{ I }^{ B }$
Type O	$ii$