Anth 2401 Lab 2 Gamete Formation

Topics: Zygosity, Allele, Genotype Pages: 7 (658 words) Published: November 13, 2013
LAB 2
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 and n while the gametes that could be produced by John would be n.

b. In each scenario below, show your work for each possibility using the different genotypes possible for John, with a series of Punnett Squares. >What are the probabilities that John and Mary will have a large nosed child? >What are the probabilities that John and Mary will have a mall-nosed child?

If Mary were to possess the homozygous dominant genotype and John the homozygous recessive genotype then there would be a 100 % (4 of 4) chance that their child would have a large nose and a 0% (0 of 4) chance that their child would have a small nose.

N
N
n
Nn
Nn
n
Nn
Nn

However, if Mary were to possess the heterozygous genotype while John possess the homozygous recessive genotype there would be a 50% chance (2 of 4) that their child would have either a large or a small nose.

N
n
n
Nn
nn
n
Nn
nn

2. Assuming the same dominant/recessive rules as in question 1, let’s look at John and Mary’s friends, Frank and Gina. Frank and Gina both have large noses. Gina has a small-nosed child. Some of their friends wonder if the child was NOT Franks! Are they wrong or right? Explain. The friends could be wrong in thinking this. On a scientific level if both Gina and Frank were to possess the heterozygous genotypes (Nn), which would undoubtedly explain their large noses, there would be a 25% (1 in 4) chance that their child would have a small nose.

N
n
N
NN
Nn
n
Nn
nn
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