Genetic Review
1. The diagram below shows 2 pairs of homologous chromosomes, with a variety of genes mapped out.
A
B
A
E
e
c
b
F
F
C
g
g
d
D
Homologous
Chromosomes
H
h
Homologous
Chromosomes
Which gene(s) are homozygous?
Which gene(s) are heterozygous?
Which gene(s) are linked to gene E?
Which gene(s) is/are most likely to become unlinked from gene E by crossing over?
2. If a female has the chromosomes shown in problem 1, what kind of egg cells can she make? (Diagram
the chromosomes and genes that could be found in the eggs produced?
Directions: Solve the following problems. Use Punnett diagrams to show your work when possible.
1. You have some pea plants with yellow seeds, but you don’t know whether they are pure or hybrids. In
peas yellow seeds are dominant over green seeds. Show on a punnett square how you would do a test
cross to determine whether plants with yellow seeds are pure or hybrid.
2. In mice, black coat color is dominant over brown coat color. A cross between a black male and a brown
female results in many offspring of which eight are brown and nine are black. What is the genotype of
both of the parent mice? Use a punnett square to explain your answer.
3. In tigers, white coat is dominant to orange. Cross a white female whose mother is orange with an orange
male. Draw a punnett square for this cross and tell the expected genotypic and phenotypic ratio of the
offspring.
4. Tallness in a particular plant is caused by a dominant allele, the flower color is determined by genes which
exhibit incomplete dominance (resulting in the colors purple, lavender and white). A tall, purple flowered
plant (heterozygous for height) is crossed with a tall, lavender-flowered plant (heterozygous for height).
What is the phenotypic ratio? Are there any two offspring from this cross that could produce short, white
flowered plants?
5. In humans, brachydactylism is the result of a dominant allele. Individuals that suffer from this trait have
very short fingers. Having a widow’s peak is the result of a dominant allele, whereas not having a widow’s
peak is recessive. Assume a female who had brachydactylism and a widow’s peak (heterozygous for both
traits) mates with a male who has normal fingers and no widow’s peak. What is the probability that their
first child will have brachydactylism and a widow’s peak? Show your work using a punnett square.
6. Two women gave birth to girls in the same hospital at the same time. The nurses think that they may have
accidently switched the babies’ nametags and given the babies to the wrong parents. One baby, Jane is
blood type O and the other baby, Mary is blood type A. The father in one set of parents, the Reds, is blood
type A and the mother is type B. The father in the other set of parents, the Greens, is blood type AB and
the mother is blood type O. Figure out which baby belongs to which parents. Explain your reasoning. Use
punnett squares.
7. Use a punnett square to show the possible genotypes and phenotypes for blood type of the offspring of
two parents. One with blood type O- and one with blood type AB+ (heterozygous for the Rh factor).
8. A. In leghorn chickens, colored feathers are due to a dominant allele, C, and white feather result from a
recessive allele, c. The presence of a dominant, P, however, prevents color in feathers, producing a white
chicken (the recessive allele, p, had no effect on color). A colored rooster is mated with a white hen and
all the chicks (400 so far) are colored. What are the probable genotypes of the parents and the offspring?
B. Can two white chickens ever produce a colored offspring? Show the possible genotypes.
C. What type of inheritance is this?
9. A sex-linked recessive allele (found on the X) determines the presence of Duchenne Muscular
Dystrophy in humans. What would be the genotypic and phenotypic results of the following
crosses?
a. A man with DMD and a woman who is a carrier
b. A man with normal muscles and a woman with DMD
c. Why can’t a man be a carrier?
10. Two gray-winged moths are mated and among the offspring are 86 white-winged, 157 gray
winged, and 79 black-winged moths. What are the genotypes of the parents? What type of cross
would result in all gray-winged offspring? What type of inheritance pattern does this follow?
11. Consider a species that has 2n = 14.
a. How many chromosomes does an individual with trisomy have?
b. How many chromosomes does an individual with monosomy have?
c. How many chromosomes does a triploid individual have?
HRHR = Red hair
HWHW = White hair HRHW = Roan (red and white)
12. What are the genotypic and phenotypic ratios of offspring when a homozygous white cow is
crossed with a roan bull?
Parent’s genotype: ___________ X _____________
What type of inheritance: __________________________
Complete the Punnett Square:
13. Define polygenic and multiple allele inheritance. Give an example of each.
14. Determine the following inheritance pattern by drawing a pedigree.
a. A man who expressing a trait marries a woman who does not express the trait. They have 3
children, two girls and a boy. Only one of the daughters expresses the trait. Both the son
and daughter that do not express the trait get married. Neither of their significant others
express the trait. The daughter has 3 children, 2 boys and 1 girl. One of the boys expresses
the trait. The son has two children, 1 girl and 1 boy. Neither expresses the trait.
Multiple Choice
_____ 1. What does DNA stand for?
a. Ribonucleic Acid
b. Don’ know
c. Deoxyribonucleic Acid
d. Genes
_____ 2. Where is DNA found?
a. Nucleus
b. Ribosomes
c. Golgi Bodies
d. Endoplasmic Reticulum
_____ 3. What are segments of DNA called?
a. segments
b. sections
c. chromosomes
d. genes
_____ 4. What do genes code for?
a. DNA
b. RNA
c. Proteins
d. Nothing
_____ 5. How is DNA arranged in the nucleus?
a. In chromosomes
b. In vacuoles
c. In punnett squares
d. In no specific order
_____ 6. What are alleles?
a. chromosomes
b. a different form of a trait
c. homozygous
d. heterozygous
_____ 7. What does homozygous mean?
a. a trait with two different alleles
b. a trait with two of the same alleles
_____ 8. What does heterozygous mean?
a. a trait with two different alleles
b. a trait with two of the same alleles
_____ 9. What is a dominant trait?
a. a trait that needs two of the alleles to be expressed
b. an allele that codes for a protein that works
c. a trait that will be expressed when an individual is heterozygous or homozygous dominant
d. both b and c
_____ 10. What is a recessive trait?
a. a trait that needs to be homozygous recessive in order to be expressed
b. an allele that codes for a protein that doesn’t work
c. a trait that will be expressed when an individual is heterozygous or homozygous dominant
d. both a and b
_____ 11. What is incomplete dominance?
a. a pattern of inheritance that has partial expression of the dominant trait when an individual is
heterozygous
b. both dominant traits are expressed
c. a trait found on the X and Y chromosomes
d. a trait determined by antigens on your blood
_____ 12. What are sex-linked traits?
a. a pattern of inheritance that has partial expression of the dominant trait when an individual is
heterozygous
b. both dominant traits are expressed
c. a trait found on the X and Y chromosomes
d. a trait determined by antigens on your blood
_____ 13. What is codominance?
a. a pattern of inheritance that has partial expression of the dominant trait when an individual is
heterozygous
b. both dominant traits are expressed
c. a trait found on the X and Y chromosomes
d. a trait determined by antigens on your blood
_____ 14. How is your blood type determined?
a. pattern of inheritance that has partial expression of the dominant trait when an individual is
heterozygous
b. both dominant traits are expressed
c. a trait found on the X and Y chromosomes
d. a trait determined by antigens on your blood
_____ 15. What are punnett squares used for?
a. determine the possible genotypes and phenotypes of 4 offspring
b. determine the possible genotypes and phenotypes of 1 offspring
c. just a fun game to be played
d. just busy work that Mr. Dock gave you to do for the last 2 weeks
1. Explain how a punnett square shows the process of meiosis, fertilization, law of segregation and the
possible phenotypic and genotypic outcomes for one offspring. After your explanation diagram and label
your explanation using the following parents: AaBb x AaBb
2. Define the each of the inheritance patterns we discussed.
3. Draw and label a homologous chromosome pair with heterozygous alleles highlighting a particular gene
location.
4. In simple dominance when does the dominant trait get expressed? When does the recessive trait get expressed?
5. How many genes per trait in all types of inheritance other than epistasis and polygenic?
6. Why do mothers pass on X linked traits to their sons? Why is it that males are more likely to get X linked
recessive disorders than females?