Genetics Lab Activity
Name:
Define the following terms (these definitions will help you answer the remaining questions)
Genotype
Phenotype
Character
Trait
Allele
Dominant Allele
Recessive Allele
Heterozygous
Homozygous
Determine the expected genotypic and phenotypic ratios of the offspring produced by the given parental
combinations…
Assume that in pea plants there are two alleles that determine flower color. Plants that possess the dominant allele (B)
have blue flower petals, while plants that are homozygous for the recessive allele (b) have white flower petals.
What genotypic and phenotypic ratios would you expect if you crossed two heterozygous pea plants?
What genotypic and phenotypic ratios would you expect if you crossed a homozygous dominant pea plant
with a homozygous recessive pea plant?
What genotypic and phenotypic ratios would you expect if you crossed a heterozygous pea plant with a
homozygous recessive pea plant?
What genotypic and phenotypic ratios would you expect if you crossed a heterozygous pea plant with a
homozygous dominant pea plant?
Determine the results of mating parental varieties that differ in two characters.
Assume that in cats there are two alleles that determine eye color and two alleles that determine fur length. Cats with
brown eyes possess the dominant allele (B) and cats with green eyes are homozygous for the recessive allele (b). Cats with
long fur possess the dominant allele (F) and cats with short fur possess the recessive allele (f).
What phenotypic ratios would you expect if you crossed a cat that is heterozygous for both eye color and fur
length with a cat that is homozygous dominant for both eye color and fur color?
What phenotypic ratios would you expect if you crossed a cat that is heterozygous for both eye color and fur
length with another cat that is heterozygous for both eye color and fur color?
What phenotypic ratios would you expect if you crossed a cat that is homozygous recessive for both eye color
and fur length with a cat that is heterozygous for both eye color and fur color?
Paternity Test?
In humans there are three alleles (IA, IB, and i) that determine ABO blood type. The genotypes and their corresponding
phenotypes are given in the table below. Use this information to answer the question below.
Genotypes
IA IA ; IAi
IB IB ; IBi
IA IB
ii
Blood Group (Phenotypes)
Type A blood
Type B blood
Type AB blood
Type O blood
Valerie has a problem, she just gave birth to a beautiful son, and she is unsure who the father is. So far
Valerie has managed to narrow the list of potential fathers down to three guys: Joe, Eddie, and Chaz. Joe has
type-A blood, Eddie has type-B blood, and Chaz has type-O blood. Valerie has type-A blood and her newborn
son Chester has type-B blood. Given this information, can you definitively tell Valerie who Chester’s father is,
or will she have to take her story to the Maury Show? If you can’t determine who the father is, can you at
least rule out one of the three potential fathers?
This time imagine that Valerie has type-A blood and her son Chester has type-O blood. This time there are
four potential fathers: Nick (type-A), Monty (type-B), Darius (type-O), and Jethro (type-AB). Given this
information, can you definitively tell Valerie who Chester’s father is? If not, can you rule anyone out?
Trihybrid Cross
Assume that in dogs there are two alleles that determine eye color, two alleles that determine fur length, and two alleles
that determine fur color. Dogs with brown eyes possess the dominant allele (B) and dogs with green eyes are
homozygous for the recessive allele (b). Dogs with long fur possess the dominant allele (F) and dogs with short fur
possess the recessive allele (f). Dogs with black fur possess the dominant allele (K) and dogs with yellow fur possess the
recessive allele (k).
What phenotypic ratios would you expect if you crossed two dogs that are both heterozygous for eye color,
fur length, and fur color?