A woman has blood Type A, her baby has blood Type AB: Is it possible that a man who has the blood Type A could be the father? Show the Punnett Square and explain.

No, it is not possible

Explanation:

Humans use the ABO blood group system where the A and B alleles are dominant over allele O but codominant with one another.

This system is such that;

Type A can only have genotype: iAiA or iAi

Type B can only have genotype: iBiB or iBi

Type AB can only have genotype: iAiB

Type O can only have genotype: ii

According to this question, a woman has blood Type A (iAiA or iAi) and her baby has blood Type AB (iAiB). This means that the father definitely contributed the allele B in order to have a baby with type AB. It also means that, according to the question, IT IS NOT POSSIBLE FOR A "Type A" father to produce that baby (see the punnet square attached).

Note: The father must contain an allele B in his genotype i.e. the father must be either type B (iBiB or iBi) or type AB (iAiB)

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.