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Genetics Practice Test



Multiple Choice
Identify the choice that best completes the statement or answers the question.
 

 1. 

Mendel prevented self-pollination of his plants by
a.
growing only one kind of plant.
b.
preventing crossing-over.
c.
removing the anthers of the plants.
d.
removing the stigmas of the plants.
 

 2. 

The “father” of genetics was
a.
T. A. Knight.
c.
Gregor Mendel.
b.
Hans Krebs.
d.
None of the above
 

 3. 

Mendel obtained his P generation by allowing the plants to
a.
self-pollinate.
c.
assort independently.
b.
cross-pollinate.
d.
segregate.
 

 4. 

What is the probability that the offspring of a homozygous dominant individual and a homozygous recessive individual will exhibit the dominant phenotype?
a.
0.25
c.
0.66
b.
0.5
d.
1.0
 

 5. 

True-breeding pea plants always
a.
are pollinated by hand.
b.
produce offspring each of which can have multiple forms of a trait.
c.
produce offspring each of which can have only one form of a trait.
d.
are heterozygous.
 

 6. 

The first filial (F1) generation is the result of
a.
cross-pollination among parents and the next generation.
b.
crosses between individuals of the parental generation.
c.
crosses between the offspring of a parental cross.
d.
self-fertilization between parental stock.
 

 7. 

Which of the following is the designation for Mendel’s original pure strains of plants?
a.
P
c.
F1
b.
P1
d.
F2
 

 8. 

F2 : F1 ::
a.
P : F1
c.
F1 : P
b.
F1 : F2
d.
dominant trait : recessive trait
 

 9. 

The passing of traits from parents to offspring is called
a.
genetics.
c.
development.
b.
heredity.
d.
maturation.
 

 10. 

A genetic trait that appears in every generation of offspring is called
a.
dominant.
c.
recessive.
b.
phenotypic.
d.
superior.
 

 11. 

homozygous : heterozygous ::
a.
heterozygous : Bb
c.
BB : Bb
b.
probability : predicting chances
d.
homozygous : BB
 

 12. 

Mendel’s finding that the inheritance of one trait had no effect on the inheritance of another became known as the
a.
law of dominance.
b.
law of universal inheritance.
c.
law of separate convenience.
d.
law of independent assortment.
 

 13. 

To describe how traits can disappear and reappear in a certain pattern from generation to generation, Mendel proposed
a.
the law of independent assortment.
b.
the law of segregation.
c.
the law of genotypes.
d.
that the F2 generation will produce only purple flowers.
 

 14. 

The law of segregation explains that
a.
alleles of a gene separate from each other during meiosis.
b.
different alleles of a gene can never be found in the same organism.
c.
each gene of an organism ends up in a different gamete.
d.
each gene is found on a different molecule of DNA.
 

 15. 

When Mendel crossed pea plants that differed in two characteristics, such as flower color and plant height,
a.
these experiments led to his law of segregation.
b.
he found that the inheritance of one trait did not influence the inheritance of the other trait.
c.
he found that the inheritance of one trait influenced the inheritance of the other trait.
d.
these experiments were considered failures because the importance of his work was not recognized.
 

 16. 

The phenotype of an organism
a.
represents its genetic composition.
b.
reflects all the traits that are actually expressed.
c.
occurs only in dominant pure organisms.
d.
cannot be seen.
 

 17. 

If an individual has two recessive alleles for the same trait, the individual is said to be
a.
homozygous for the trait.
b.
haploid for the trait.
c.
heterozygous for the trait.
d.
mutated.
 

 18. 

An individual heterozygous for a trait and an individual homozygous recessive for the trait are crossed and produce many offspring. These offspring are likely to be
a.
all the same genotype.
b.
of two different phenotypes.
c.
of three different phenotypes.
d.
all the same phenotype.
 

 19. 

Tallness (T) is dominant over shortness (t) in pea plants. Which of the following represents the genotype of a pea plant that is heterozygous for tallness?
a.
T
c.
Tt
b.
TT
d.
tt
 
 
In humans, having freckles (F) is dominant over not having freckles (f). The inheritance of these traits can be studied using a Punnett square similar to the one shown below.

nar001-1.jpg
 

 20. 

Refer to the illustration above. The genotype represented in box 1 in the Punnett square would
a.
be homozygous for freckles.
b.
have an extra freckles chromosome.
c.
be heterozygous for freckles.
d.
have freckles chromosomes.
 

 21. 

Refer to the illustration above. The genotype in box 3 of the Punnett square is
a.
FF.
c.
ff.
b.
Ff.
d.
None of the above
 

 22. 

A trait that occurs in 450 individuals out of a total of 1,800 individuals occurs with a probability of
a.
0.04.
c.
0.50.
b.
0.25.
d.
0.75.
 

 23. 

How many different phenotypes can be produced by a pair of codominant alleles?
a.
1
c.
3
b.
2
d.
4
 
 
nar002-1.jpg
 

 24. 

Refer to the illustration above. The phenotype represented by box 1 is
a.
green, inflated.
c.
yellow, inflated.
b.
green, constricted.
d.
yellow, constricted.
 

 25. 

Refer to the illustration above. The genotype represented by box 2 is
a.
GgIi.
c.
GI.
b.
GGIi.
d.
Gi.
 

 26. 

2,000 yellow seeds : 8,000 total seeds ::
a.
1 : 6
c.
1 : 3
b.
1 : 8
d.
1 : 4
 
 
In rabbits, black fur (B) is dominant over brown fur (b). Consider the following cross between two rabbits.

nar003-1.jpg
 

 27. 

Refer to the illustration above. The device shown, which is used to determine the probable outcome of genetic crosses, is called a
a.
Mendelian box.
c.
genetic graph.
b.
Punnett square.
d.
phenotypic paradox.
 

 28. 

Refer to the illustration above. Both of the parents in the cross are
a.
black.
b.
brown.
c.
homozygous dominant.
d.
homozygous recessive.
 

 29. 

Refer to the illustration above. The phenotype of the offspring indicated by box 3 would be
a.
brown.
b.
black.
c.
a mixture of brown and black.
d.
The phenotype cannot be determined.
 

 30. 

Refer to the illustration above. The genotypic ratio of the F1 generation would be
a.
1:1.
c.
1:3.
b.
3:1.
d.
1:2:1.
 

 31. 

What is the expected genotypic ratio resulting from a homozygous dominant ´ heterozygous monohybrid cross?
a.
1:0
c.
1:2:1
b.
1:1
d.
1:3:1
 

 32. 

What fraction of the offspring resulting from a heterozygous ´ heterozygous dihybrid cross are homozygous recessive for both traits?
a.
9/16
c.
3/16
b.
1/4
d.
1/16
 

 33. 

What is the expected genotypic ratio resulting from a heterozygous ´ heterozygous monohybrid cross?
a.
1:2:1
c.
1:2
b.
1:3:1
d.
1:0
 

 34. 

What is the expected phenotypic ratio resulting from a homozygous dominant ´ heterozygous monohybrid cross?
a.
1:3:1
c.
2:1
b.
1:2:1
d.
1:0
 
 
nar004-1.jpg
 

 35. 

Refer to the illustration above. The phenotype represented by box 1 is
a.
round, yellow.
c.
wrinkled, yellow.
b.
round, green.
d.
wrinkled, green.
 

 36. 

Refer to the illustration above. The genotype represented by box 2 is
a.
RRYY.
c.
RrYy.
b.
RrYY.
d.
rrYy.
 

 37. 

Refer to the illustration above. Which of the following boxes represents the same phenotype as box 7?
a.
3
c.
5
b.
4
d.
6
 

 38. 

An organism that has inherited two of the same alleles of a gene from its parents is called
a.
hereditary.
c.
homozygous.
b.
heterozygous.
d.
a mutation.
 

 39. 

In pea plants, yellow seeds are dominant over green seeds. What would be the expected genotype ratio in a cross between a plant with green seeds and a plant that is heterozygous for seed color?
a.
1:3
c.
4:1
b.
1:2:1
d.
1:1
 

 40. 

codominance : both traits are displayed ::
a.
probability : crosses
b.
heterozygous : alleles are the same
c.
homozygous : alleles are the same
d.
Punnett square : chromosomes combine
 

 41. 

The difference between a monohybrid cross and a dihybrid cross is that
a.
monohybrid crosses involve traits for which only one allele exists, while dihybrid traits involve two alleles.
b.
monohybrid crosses involve self-pollination, while dihybrid crosses involve cross-pollination.
c.
monohybrid crosses involve one trait; dihybrid crosses involve two traits.
d.
dihybrid crosses require two Punnett squares; monohybrid crosses need only one.
 

 42. 

What fraction of the offspring resulting from a heterozygous ´ heterozygous dihybrid cross are heterozygous for both traits?
a.
9/16
c.
3/16
b.
1/4
d.
1/16
 

 43. 

A cross of two individuals for a single contrasting trait is called
a.
monohybrid.
c.
dominant.
b.
dihybrid.
d.
codominant.
 

Completion
Complete each statement.
 

 44. 

The transferring of pollen between plants is called ____________________.
 

 

 45. 

Mendel produced true-breeding strains of pea plants through the process of ____________________.
 

 

 46. 

When two members of the F1 generation are allowed to breed with each other, the offspring are referred to as the ____________________ generation.
 

 

 47. 

In heterozygous individuals, only the ____________________ allele achieves expression.
 

 

 48. 

The statement that the members of each pair of alleles separate when gametes are formed is known as the _________________________.
 

 

 49. 

Different forms of a particular gene, which Mendel called factors, are now called ____________________.
 

 

 50. 

The cellular process that results in the segregation of Mendel’s factors is ____________________.
 

 

 51. 

The portion of a DNA molecule containing the coded instructions that result in a particular characteristic of an organism is called a(n) ____________________.
 

 

 52. 

An organism’s ____________________ refers to the set of alleles it has inherited.
 

 

 53. 

The likelihood that a specific event will occur is called ____________________.
 

 

 54. 

co054-1.jpg

Refer to the illustration above. The box labeled “X” represents the phenotype ____________________.
 

 

 55. 

A fractional probability of 1/2 is the same as a decimal probability of ____________________.
 

 
 
In pea plants, tallness (T) is dominant over shortness (t). Crosses between plants with these traits can be analyzed using a Punnett square similar to the one shown below.

nar005-1.jpg
 

 56. 

Refer to the illustration above. The parents shown in the Punnett square are likely to have offspring with a genotype ratio of ____________________.
 

 

 57. 

Refer to the illustration above. Box 2 and box ____________________ in the Punnett square represent plants that would be heterozygous for tallness.
 

 

 58. 

Refer to the illustration above. The phenotype of the plant that would be represented in box 4 of the Punnett square would be ____________________.
 

 

 59. 

Refer to the illustration above. The genotype of both parents shown in the Punnett square above is ____________________.
 

 

 60. 

A situation in which both alleles for a trait are expressed in a heterozygous offspring is called ____________________.
 

 

 61. 

A pattern of heredity in which a heterozygous individual has a phenotype that is intermediate between the phenotypes of its two homozygous parents is called _________________________.
 

 

 62. 

A table used to determine and diagram the results of a genetic cross is called a ____________________.
 

 

 63. 

In genetics, lowercase letters are usually used to indicate ____________________.
 

 

Problem
 

 64. 

In tomato plants, tallness is dominant over dwarfness and hairy stems are dominant over hairless stems. True-breeding (homozygous) plants that are tall and have hairy stems are available. True-breeding (homozygous) plants that are dwarf and have hairless stems are also available. Design an experiment to determine whether the genes for height and hairiness of stem are on the same or different chromosomes. Explain how you will be able to determine from the results whether the genes are on the same chromosome or different chromosomes, and whether they are close to each other or far apart if they are on the same chromosome. Write your answer in the space below.
 

 65. 

A scientist crossed true-breeding tall and hairy-stemmed tomato plants with true-breeding dwarf and hairless-stemmed tomato plants. He found that all of the F1 plants produced as a result of this cross were tall and hairy-stemmed. He then allowed the F1 plants to pollinate each other and obtained 1000 F2 plants. Of these 1000 F2 plants, he observed the following numbers of four different phenotypes:

557 tall and hairy-stemmed plants192 dwarf and hairy-stemmed plants
180 tall and hairless-stemmed plants 71 dwarf and hairless-stemmed plants

Write your answers to the following in the space below or on a separate sheet of paper.
a.      Which height characteristic is dominant, tallness or dwarfness?
b.      Which stem characteristic is dominant, hairiness or hairlessness?
c.      What are the genotypes of the original, true-breeding parents? (Be sure to indicate what the symbols you use stand for.)
d.      What are the genotypes of the F1 hybrid plants? (Be sure to indicate what the symbols you use stand for.)
e.      What are the genotypes of the four types of plants found in the F2 generation? (Be sure to indicate what the symbols you use stand for.)
f.      What were the expected numbers of plants of each type in the F2 generation? (Round off to the nearest whole numbers.)
g.      Why did the observed numbers of plants of each type in the F2 generation differ from the expected?
h.      How could this experiment have been changed to obtain numbers of plants of each type in the F2 generation that were closer to the expected numbers?
 

Essay
 

 66. 

How might you go about determining the genotype of a red-flowering plant where red is dominant over white? Write your answer in the space below.
 

 67. 

Describe pollination in pea plants. Write your answer in the space below.
 

 68. 

In what ways did Mendel’s methods help ensure his success in unraveling the mechanics of heredity? Write your answer in the space below.
 

 69. 

What conclusions did Gregor Mendel reach based on his observations of pea plants? Write your answer in the space below.
 

 70. 

Describe Mendel’s observation regarding independent assortment. Write your answer in the space below.
 

 71. 

What are three ways to express the probability of an event that occurs 500 times out of 2,000 total trials? Write your answer in the space below.
 

 72. 

Describe how genotype and phenotype are related, and give an example. Write your answer in the space below.
 

 73. 

Explain what is meant by homozygous and heterozygous, and give an example of each. Write your answer in the space below.
 

 74. 

All of the offspring resulting from a cross between a red snapdragon and a white snapdragon are pink. What is a possible explanation for this? Write your answer in the space below.
 



 
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