Mendelian Genetics Assignment
Name or Names (if you worked in a group):
Brandon Woodruff
1.
A certain dominant gene causes some people in the population to be born with 6 fingers (F) instead
of 5 (f). Another dominant gene causes dwarfism (D) while normal height (d) is recessive.
A father, Barry, has six fingers and has dwarfism (he is heterozygous for both traits). The mother,
Jill, has 5 fingers and is also a dwarf. Jill’s father, Sam, is of normal height.
List the genotypes of Barry and Jill, then figure out the possible resulting gametes for each:
Barry’s genotype:
Fd/Fd
Jill’s genotype: Fd/d
Barry’s gametes:
F, d
Jill’s gametes: F,d
Complete the dihybrid cross using the gametes produced by Jill and Barry:
F
F
FF
6 fingers, normal
Height
F
d
Fd
6 fingers, dwarf
d
F
Fd
6 fingers, dwarf
d
d
fd
5 fingers, dwarf
1.
What percent/ratio of the offspring will be heterozygous for both traits? 50
2.
What percent/ratio of the population will have 5 fingers and be of normal height? 25
3.
What percent/ratio of the dwarfs’ offspring will be of normal height? 25
4.
In a paternity case, a mother, Jenny, claimed that the father of her child was Billy. Billy claimed that
the father of the child was her current boyfriend, Fred. The child has blood type A, Billy has AB
blood, and Jenny has type B blood. Fred is heterozygous for blood type A.
a. List the genotypes of Jenny, Billy, and Fred using proper letters (IA, IB, and i)
Jenny: IB
Billy: IAIB
Fred: IAi
b. Complete the monohybrid crosses for both Jenny and Billy and for Jenny and Fred:
Jenny and Billy
IA
Jenny and Fred
IB
IA
I
IAI
IBI
IAI
IBi
IAI
IBI
IAI
IBi
IB
IB
Type A: 0%
Type A: 50%
Type B: 100%
Type B: 50%
c. List the phenotypic frequencies under each monohybrid cross.
d. What are the chances that Jenny and Billy would have a child with Type A blood?
There is a 0% chance that they have a child with Type A blood.
e. What are the chances that Jenny and Fred would have a child with Type A blood?
There is a 50% chance that they have a child with Type A blood.
f.
With the information given, can you determine the father of the child? If so, who is it?
Yes, because the blood type of the child is Type A, the father must be heterozygous for Type A.
Because of that, Fred is the only possible father.
5.
The ABO gene contains three alleles IA, IB, and i. and are co-dominant. Another gene (Rh)
determines whether a person is “+” or “-“, and the Rh+ allele is dominant to the Rh- allele. A man
with type B+ blood and a woman with A+ blood have a child with O- blood. What is the genotype of
the man in this problem?
The man in this problem must be heterozygous for the ABO gene, with one IB allele and one i allele.
This is because the woman has blood type A, which means she must have two IA alleles. The child
has blood type O, which means they must have two i alleles. The only way for the child to inherit
two i alleles is if the father passes on one i allele and the mother passes on the other i allele.
The man's genotype for the Rh gene is unknown, as he could be either Rh+ or Rh-. However, the
fact that the child has blood type O does not necessarily mean that the child cannot be Rh+. This is
because Rh+ blood is not always co-dominant with O blood; it is possible for a person with Rh+
blood to have a child with O blood if the child inherits two i alleles from the mother. Therefore, the
man's genotype for the Rh gene could be either Rh+ or Rh-.