Genetics Practice Exam
10 points
Name _______________
Date ___________
Class Period _______
Matching (2pts each)
_G__ 1. Gamete
__I_2. DNA
B. Trait
__E_3. Dominant
_C__4.
A. Used to trace genes through family trees
Homozygous
C. Having two of the same genes for the same
trait
D. Trait found on the X chromosome
__K_ 5. Mitosis
E. Masks the recessive trait
__D_ 6. X-linked
F. Sperm
___B_7. Characteristic
G. Determine the sex of an organism
_L___ 8. Huntington Disease
H. What the genes say or code
__A__ 9. Pedigree
I. Molecule that contains the genetic information
__H__ 10. Genotype
J. New
K Cell duplication or growth
L. Produces muscle weakness and cataracts
Fill in the blank. (2pts each)
1. A mutation is a physical change in the _____DNA___________ of an
organism.
2. A heterozygous pair of chromosome has one dominant gene and one
____Recessive____________ gene.
3. Messenger RNA carries the genetic code to the ribosomes where they make the
correct ______Protein_________.
Fill in the blank continued
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4. ______Probability________________ is used to calculate the chances of
something happening.
General Formula for Probability:
Occurrence/ Possible Outcomes
Eg. A coin- Occurrence would be heads or tails (1). Possible outcomes is 2
(heads or tails)
5. Haploid is __half_____________ the number of chromosomes of somatic
(regular) cells.
Short answers. Write complete sentences. (5pts each)
1. Explain how the sex of the baby is caused in humans and why half of the
population is male and half female.
In humans the egg always carries and X chromosome. At fertilization the
sperm that fertilizes the egg is either carrying an X chromosome or a Y
chromosome but not both. There is a 50% chance that the sperm is carrying X and
a 50% chance it is carrying Y. Because the chances are 50/50 half the population
is female and half is male.
2. Who was Gregor Mendel? Describe his research and explain why he is called
the father of genetics.
Gregor Mendel was an Austrian monk who performed experiments using pea
plants. His experiments which were not appreciated during his lifetime provide
the basis for what is now known as Mendelian Genetics. Mendelian Genetics
describes dominance, recessivness, independment assortment of genes and
other concepts which are the basis of genetics today.
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3. A Reebop is a marshmallow creature. There is a Reebop around that has the
following genotype for several traits:
DD (Dd)
Aa
Nn
Using the following table, how many dominant, codominant and recessive traits is
the Reebop expressing? Dominant- one (three body segments)
Codominant- TWO- one antennae, orange nose
Recessive- Zero
Genotype
DD
Dd
dd
AA
Aa
aa
NN
Nn
nn
Phenotype
Three body segments
Three body segments
Two body segments
Two antennae
One antennae
No antennae
Pink Nose
Orange Nose
Green Nose
Define the following. Write complete sentences. One point will be lost for each
incomplete sentence written. (3pts each)
1. Phenotype - The phenotype is the physical expression of the genotype.
2. Carrier- A carrier has one copy of a recessive allele that is masked by the
dominant allele so they have the dominant phenotype.
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3. Codominance- Codominance is a situation where the phenotype is between the
dominant phenotype and the recessive phenotype. The reebops had many
codominant traits such as one antennae and orange noses.
4. Allele- An allele is a form of a gene, for example the genes for blue eyes,
green eyes and brown eyes are all alleles
Multiple choice. Circle the correct answer (2pts each)
1. What is a gene?
a. A section of DNA that codes one trait
b. A chromosome
c. A whole strand of DNA
d. None of the above
2. A plant with the genotype RR is crossed with a plant with the genotype rr.
What percentage of the offspring would be predicted to have the genotype Rr?
a. 25%
b. 50%
c. 75%
d. 100%
3. A human skin cell contains
a. 4 chromosomes
b. 16 chromosomes
c. 23 chromosomes
d. 46 chromosomes
4. What letters stand for the bases that make the genetic code in DNA?
a. FGAT
b. CGUA
c. CGAT
d. GADC
5. A human with the chromosomes XX is
a. A male.
b. A dwarf.
c. A female
d. An example of failure of genes to separate during meiosis.
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6. Mitotic division produces two daughter cells with a _______ number of chromosomes, while
meiosis produces four daughter cells with a _______ number of chromosomes.
A. haploid, diploid
B. diploid, haploid
C. haploid, haploid
D. diploid, diploid
7. A recessive allele t is responsible for a condition called distonia. A man who has this condition
marries a woman who doesn't. One of their four children has the condition. What are the possible
genotypes of the man and woman?
A. The father is Tt; the mother is TT.
B. Both parents are tt.
C. The father is tt; the mother is TT.
D. The father is tt; the mother is Tt.
8. An expert in x-ray crystallography this scientist took a photo that was critical to the discovery
of the structure of DNA in the 1950’s
A. Oswald Avery
B. Herbert Boyer
C. Rosalind Franklin
D. Barbara McClintock
E. James Watson
9. A gene showing codominancea.
has both alleles independently expressed in the heterozygote
b.
has one allele dominant to the other
c.
has alleles tightly linked on the same chromosome
d.
has alleles expressed at the same time in development
e.
has alleles that are recessive to each other
10. Replication of DNA:
a. takes place in a “conservative” manner
b. takes place in a “dispersive” manner
c. takes place in a “semi-conservative” manner
d. usually involves one origin of replication per chromosome
e. in eukaryotes takes place only in the cytoplasm
Probability (3pts each)
1. What is the probability of flipping four pennies and having all four come up as heads?
1 in _16_____
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2. What is the probability of tossing two 6-sided die and having both come up on the number
4?1 in ___36___
3. Shown below is a representation of a fruit fly's 10 chromosomes, 5 of which it inherited from
its father (depicted in dark) and 5 of which it inherited from its mother (depicted in light).
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What is the probability that a particular sperm cell produced by this fly contains copies of the 5
chromosomes that were inherited from the fly's mother, as shown below?
The probability =1 in __32_____
Extra credit Probability Problems
1. If the father is heterozygous for eye color, and the mother is also heterozygous
for eye color what is the chance that the offspring will inherit two homozygous
recessive chromosome? (1pt)
1 in __4__
2. This problem concerns three traits found on three different chromosomes in pea
plants. The first trait is for height of the plant where tall is dominant (T) over short
(t). The second is for the color of the seed where green (G) is dominant over
yellow (g) and the third trait is the texture of the seed coat where round (R) is
dominant over wrinkled (r). A heterozygous tall, heterozygous green seeded,
heterozygous yellow plant (Tt,Gg,Rr) is crossed with an identical plant (Tt,Gg,Rr).
What is the probability that a plant that is all homozygous recessive will be
produced? (tt,gg,rr) (5pts)
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1in _64__
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