Question

Ms. B. continued her explanation. “Everyone has two alleles for each gene in their cells. We all inherited one allele for every gene from each of our parents. Since your mom is type A, she could have two copies of allele A or one copy of allele A and one copy of allele O. In either case, she is type A. Your father could … ”

“His father could have two copies of allele B or one copy of allele B and one copy of allele O. Either way, he is type B,” Peter said.

“Yes, you’re getting smarter,” smiled Ms. B. “Keep going. Think. If Kevin’ s mom has one copy of allele A and one of allele O, and his dad has one copy of allele B and one of allele O, then what possible blood types will their children have?”

“Oh, let me think,” Peter and Kevin said simultaneously.

Questions

1. What is genetic inheritance?
2. Among the three alleles of human ABO blood group, which is/are dominant, which is/are recessive?
3. What is homozygous? What is heterozygous? Are Kevin’s parents homozygous or heterozygous for the A or B allele if Ms. B’s assumption is true?
4. Predict the possible blood types of their children from the marriage of Kevin’s parents. Use a Punnett square to solve this problem.

5. What are the probabilities (%) of the children’s possible blood types?

Answer 1

Genetic Inheritance-

The resulting offspring from the parents will have the genes from both father and mother which show the effect of their genes in the offspring. It shows how certain characteristics are passed from parents to the offsprings. In the offsprings some genes who their effects are dominant genes which dominated the genes of another person in the parent. There are certain disorders due to genetic inheritance that can pass from parents to offspring during the gene transfer. Some examples of genetic disorders are Autosome or Sex-linked disorders.

Blood Type	Antigen present on RBC	Antibodies present in blood	Can donate blood to the person having blood group	Can receive blood from
A	A	b	A	A and O
B	B	a	B	B and O
AB(Universa recipient)	A,B	-	AB	A, B, AB and O
O(universal donor)	-	a,b	A, B, AB, O	O

Phenotype (blood group)	Homozygous genotype	Heterozygous genotype
A	Ia Ia	Ia Io
B	Ib Ib	Ib Io
AB	-	Ia Ib
O	Io Io	-

Homozygous alleles will have two copies of alleles while the heterozygous will have a single copy of alleles.

If the assumptions are true then the Kevin's parents are heterozygous for that allele we can say this by the help of above table.

Blood type inheritance

Dominant blood group - These are those blood groups that show their effect on the blood group. Out of A, B, and O A and B blood groups are dominant and which can not show their effect will have the recessive blood group which is  Blood group O.

Blood group - AB in which A and B are codominant

If the genotype of Kevin's mom is Ia Io and the genotype of Kevin's father is Ib Io  then the childre will have the following phenotype

	Ib	Io
Ia	Ia Ib	Ia Io
Io	Ib Io	Io Io

The Kevin's parents will have the offspring of possible genotypes

Out of four children, one has genotype Ia Ib which means that there is 1/4 or 25% probability that their children will have Blood group AB.

The same will happen in other cases There is equal probability of each blood group in the children.

There is 1/4 or 25% probability that their children will have Blood group A

There is 1/4 or 25% probability that their children will have Blood group B

There is 1/4 or 25% probability that their children will have Blood group O