Genetics, Heredity, and Probability
Quiz Study Guide
Important Reminders:
 Capital letters = Dominant (R)
 Lowercase letter = Recessive (r)
 RR + WW (two sets of capital alleles) = Incomplete dominance, both
traits partially show, “mixing” of traits (red male+ white female = pink
offspring)
 FWFW + FBFB (letters with superscript) = Codominance, both traits
completely show (black male + white female = black and white
offspring)
 In a Punnett Square, write the male’s alleles across the top and the
female’s down the left side (one allele per each box on the outside,
two alleles per each box on the inside)
 When calculating percentages using a Punnett Square:
o 1/4 = 25/100 = 25%
o 2/4 = 50/100 = 50%
o 3/4 = 75/100 = 75%
o 4/4 = 100/100 = 100%
Complete the Following Practice Problems:
1. How did Gregor Mendel’s studies with pea plants contribute to the
study of genetics? Answer in THREE or more COMPLETE
SENTENCES.
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2. Match the following terms with their definitions.
Heredity___
a. each different form of a characteristic
Dominant Allele___ b. passing of physical characteristics from parent to offspring
Recessive Allele___ c. the scientific study of heredity
Homozygous___
d. trait always shows up when allele is present
Phenotype___
e. hidden whenever dominant allele is present
Probability___
f. a number that describes how likely an event will occur
Heterozygous___
g. organism’s physical appearance
Genotype___
h. organism’s genetic makeup or allele combination
Genes___
i. organism that has two identical alleles for a trait
Trait___
j. organisms that has two different alleles for a trait
Codominance___
k. alleles are neither dominant nor recessive, both are equally
Expressed in offspring
Genetics___
l. factors that control a trait
3. In the following questions, B = black, and b = white
I have a cat that is heterozygous for black fur. What is its genotype?
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I have a cat that is homozygous for white fur. What is its genotype?
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I have a cat that has Bb for a genotype. What is its phenotype?
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I have a male cat that is homozygous for black fur. I cross this cat
with a female cat that is heterozygous for black fur. Draw a Punnett
Square to show the possible outcomes for the offspring of this cross.
What is the probability (percent) that the offspring will have black
fur?
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What is the probability that the offspring will have white fur?
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What is the probability that the offspring will have a homozygous
allele combination?
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4. In the following questions, FB= Blue, and FY= Yellow.
What is the phenotype for a parrot with the allele combination FBFY?
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I have a male parrot that is homozygous for blue feathers. I cross this
male with a female parrot that is homozygous for yellow feathers. Draw a
Punnett Square to show the possible outcomes for the offspring of this
cross.
What is the probability that the offspring will have ONLY blue
feathers?
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What is the probability that the offspring will have BOTH yellow AND
blue feathers?
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5. In the following questions, B = blue, and R = red.
I have a fish that is homozygous for blue scales. What is its genotype?
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What is the phenotype for a fish with the genotype BR?
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