Exercise 2.A. Gamete Formation
1. What are the gamete combinations that can be produced by the following individuals?
a. AABB- AB
b. AaBB- AB and aB
c. AAABBcc- ABc
d. AAbbCc- AbC and Abc
e. AaBbCc- ABC, ABc, AbC, Abc, aBC, aBc, abC and abc
2. What are the possible genotypes of the offspring from mating of the following individuals? (the x refers to the mating. In the first, you would place EE along the top and ee on the side or vice versa).
a. EE x ee
E
E
e
Ee
Ee e Ee
Ee
b. Ee x Ee
E e E
EE
Ee e Ee ee c. AaBb x AAbb
A a B b A
AA
Aa
AB
Ab
A
AA
Aa
Ab
Ab
b
Ab
ab
Bb
bb b Ab ab Bb bb d. AaBbCC x AABBCc
A a B b C
C
A
AA
Aa
AB
Ab
AC
AC
A
AA
Aa
AB
Ab
AC
AC
B
AB
Ba
BB
Bb
BC
BC
B
AB
Ba
BB
Bb
BC
BC
C
AC
Ca
BC
Cb
CC
CC c Ac ac Bc bc Cc
Cc
e. EeBBcc x eebbCC
E e B
B
c c e
Ee
ee
Be
Be ec ec e Ee ee Be
Be
ec ec b
Eb
eb
Bb
Bb bc bc b Eb eb Bb
Bb
bc bc C
EC
Ce
BC
BC
Cc
Cc
C
EC
Ce
BC
BC
Cc
Cc
Exercise 2.B
1. Imagine that nose size is a phenotype expression of the gene N. Let’s agree that large nose size (N) is dominant and small nose size is recessive (n). John has a small nose and Mary has a large nose.
a. We don’t know John’s genotype, but we have a good idea of Mary’s genotype. Why? What are the possible genotypes for each? What are the possible gametes that can be produced by each?
Because Mary’s phenotype expression is dominant it is possible for Mary to have several variations of genotypes which would possess the dominant allele which could be either homozygous or heterozygous whereas John’s recessive phenotype could only be present through a homozygous recessive genotype. The possible genotypes for Mary would include the homozygous dominant (NN) or a heterozygous (Nn) while John would possess the homozygous recessive (nn). The possible gametes that could be produced by Mary would be N