Biological Sciences Division
Week 4
Introduction to Genetics & Evolution
(1.20103)
Practical Activity #1
COMPLETE DOMINANCE INHERITANCE PATTERNS
SINGLE-TRAIT CROSS GENETIC PROBLEMS
1)
Define the following terms used in genetics:
i) Homozygous
ii) Heterozygous
iii) Alleles
iv) Genes
v) Genotype
vi) Phenotype
2)
Create a punnet square (without the calculations) with keys for a homozygous dominant black
mouse that was mated with a homozygous recessive white mouse.
3)
Prepare a punnet cross of a homozygous tall plant with a homozygous short plant. Assign your
letters in a key before you do the cross.
a. What is the phenotypic outcome of the cross?
b. What are the genotypes from this cross?
4)
Pink flower trait is dominant over white flowers in 4’oclock plants. If a heterozygous purple flower
was crossed with a white flower, what would be the ratio of purple flowered plants to white
flowered plants? Use a punnet square to solve this problem.
.
Attached earlobes are dominant trait over unattached earlobes. If a man who has unattached
earlobes had children with a women who had attached earlobes, what are the chances of any of
their children having unattached earlobes like him? And how did you arrive at your conclusion?
5)
vii) Self-fertilization
viii) Cross-fertilization
ix) Clone
x) Hybrid
xi) Punnet square
4)
Purple guava fruit bearing trees are rarely seen compared to green and yellow fruit guava trees. If
the flowers of yellow fruit guava tree were cross bred with that of a purple fruit guava flowers,
what do you expect the outcome hybrids to be?
5)
Choose the correct terms to describe the genotypes below.
g)
a) DD =
h)
b) Ee =
i)
c) ff =
j)
d) mm =
k)
e) Mm =
l)
f) SS =
1
rR =
rr =
hH =
jj =
Ll =
YY =
6) In Melanesians, shades of brown hair (H) colour is dominant over black hair (h) color.
a) What hair colour would correspond to the following genotypes?
i) HH =
ii) Hh =
iii) hh =
7) Heterozygous smooth pea pod plant is cross with a wrinkled pea pod plant.
a) What are the genotypes of the parents?
b) What are the possible gametes of each parent?
c) What are the genotypes of the possible offspring?
d) What is the phenotypic ratio of the offspring?
e) What is the genotypic ratio of the offspring?
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