Question

1) Answering the following genetics problems using punnett squares and determine the type of inheritance of each. State phentypes as a %.

A. A woman with AB blood type marries a man with BO blood type. What are the possible genotypes of their

offspring?

B. Rh+ factor is dominant over Rh- factor. A man who is Rh- marries a woman who is heterozygous for Rh

factor. What is the likelihood that they will have a child who is Rh+?

C. A woman with type A- blood gave birth to a baby with type O+ blood. She is unsure which of two men

fathered the child. Using what you know about Mendelian genetics and ABO blood typing, determine

whether Ralph or Joe is the baby’s father. Ralph: BO+-, Joe: AO—

D. The trait for magical ability is a recessive trait among Muggles. Harry’s mother was the first person in her

family to have the wizarding trait. Her sister, Petunia, was a Muggle. Petunia married Vernon and they

had one son, Dudley who was a Muggle. Dudley married a Muggle named Eleanor and to their horror,

they had a daughter, Poopsie, who was a wizard. Create a pedigree of Harry’s family. Determine the

genotype of: Harry’s maternal grandparents, Petunia, Vernon, Dudley, Eleanor, and Poopsie.

E. In vampires, the heterozygous condition of red (R) and yellow (r) eye color alleles produces orange-eyed

baby vampires. What type of inheritance is this? (see your text) Cross a red-eyed vampire with a yellow-

eyed vampire and determine their possible offspring.

Answer 1

Parental genotype (father or mother)	Parental genotype (father or mother)	Offspring’s genotype (on mating)
AO	BO	AB BO	AO OO
AA	BB	AB AB	AB AB
AA	BO	AB AB	AO AO
AA	OO	AO AO	AO AO
AO	OO	AO OO	AO OO
AB	OO	AO BO	AO BO

Phenotype for ABO blood group is induced according to the genotype as:

1) Blood group A phenotype- for genotype A/A or A/O

2) Blood group B phenotype-for genotype B/B or B/O

3) Blood group AB phenotype-for genotype A/B

4) Blood group O phenotype-for genotype O/O

Answers:

A.

• Blood group of woman = AB, genotype = AB
• Blood group man= B, genotype = BO
• Cross: AB xBO

	B	O
A	AB	AO
B	BB	BO

F1 (Offspring)

Blood group	Genotype obtained	Probability
AB	AB	1/4
A	AO	1/4
B	BB/BO	1/2

B.

Representation:

Blood group of woman = Rh positive = Rr (heterozygous)

Blood group of man = Rh negative = rr

Rr x rr

	r	r
R	Rr	Rr
r	rr	rr

F1 (offspring)

Rr= Rh positive = ½

rr= Rh negative =1/2

C.

Representation:

Blood group of woman =A negaive = AORr (heterozygous as child is O+)

Blood group of Ralph = B positive = BORr

Cross with Ralph : AORr x BORr

For AO x BO

	B	O
A	AB	AO
O	BO	OO
For Rr x rr
	R	r
R	Rr	Rr
r	Rr	rr

Blood group of Joe = A negaive = AOrr

For AO x AO

	A	O
A	AA	AO
O	OO	OO
For Rr x rr
	r	r
R	Rr	Rr
r	rr	rr

Thus, there is more chance of Joe to produce O+ child.

D.

Representation:

Muggle trait = WW (Homozygous dominant)/ Ww (Heterozygous dominant)

Wizarding trait = ww

• Harry's mother was a wizard, her genotype = ww
• Harry was a wizard = ww
• Since, Dudley (being muggle) and marrying Eleanor (also muggle) has wizard child Poopsie, thus both are heterozygous.
• Hence, Dudley's genotype = Ww
• Eleanor's genotype = Ww.
• Poopsie's genotype = ww.
• Thus, Petunia was a heterozygous, genotype = Ww.
• Vernon was probably homozygous dominant= WW

Ww x Ww (Dudley x Eleanor)

	W	w
W	WW	Ww
w	Ww	ww

Representation:

• Red= R = dominant, genotype= RR (Homozygous)/Rr Heterozygous)

• Yellow = r= recessive, genotype= rr

Rr x rr

	r	r
R	Rr	Rr
r	rr	rr

Rr = Orange

rr= yellow

It depicts incomplete dominance.

• When a trait is in form of intermediate inheritance, in which an allele is not specifically expressed over its paired allele, then it results in a third phenotype, expressed as combination of phenotypes of both the alleles. This condition is referred to as incomplete dominance.