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					Genetics Practice Test

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

____    1. The “father” of genetics was
           a. T. A. Knight.                                   c. Gregor Mendel.
           b. Hans Krebs.                                     d. None of the above
____    2. 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
____    3. Which of the following is the designation for Mendel’s original pure strains of plants?
           a. P                                               c. F1
           b. P1                                              d. F2
____    4. A genetic trait that appears in every generation of offspring is called
           a. dominant.                                       c. recessive.
           b. phenotypic.                                     d. superior.
____    5. 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.
____    6. If an individual has two recessive alleles for the same trait, the individual is said to be
           a. homozygous for the trait.                       c. heterozygous for the trait.
           b. haploid for the trait.                          d. mutated.
____    7. An individual heterozygous for a trait and an individual homozygous recessive for the trait are crossed and
           produce many offspring that are
           a. all the same genotype.                          c. of three different phenotypes.
           b. of two different phenotypes.                    d. all the same phenotype.
____    8. Tallness (T) is dominant to shortness (t) in pea plants. Which of the following represents a 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 to not having freckles (f). The inheritance of these traits can be
            studied using a Punnett square similar to the one shown below.
____  9. 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.
____ 10. 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
____ 11. 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.
____ 12. How many different phenotypes can be produced by a pair of codominant alleles?
         a. 1                                               c. 3
         b. 2                                               d. 4




____ 13. Refer to the illustration above. The phenotype represented by the cell labeled “1” is
         a. green, inflated.                              c. yellow, inflated.
         b. green, constricted.                           d. yellow, constricted.
____ 14. Refer to the illustration above. The genotype represented by the cell labeled “2” is
         a. GgIi.                                         c. GI.
         b. GGIi.                                         d. Gi.

            In rabbits, black fur (B) is dominant to brown fur (b). Consider the following cross between two rabbits.
____ 15. 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.
____ 16. Refer to the illustration above. Both of the parents in the cross are
         a. black.                                         c. homozygous dominant.
         b. brown.                                         d. homozygous recessive.
____ 17. Refer to the illustration above. The phenotype of the offspring indicated by box “3” would be
         a. brown.                                         c. a mixture of brown and black.
         b. black.                                         d. The phenotype cannot be determined.
____ 18. 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.
____ 19. 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
____ 20. 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
____ 21. 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
____ 22. 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
____ 23. Refer to the illustration above. The phenotype represented by the cell labeled “1” is
         a. round, yellow.                                 c. wrinkled, yellow.
         b. round, green.                                  d. wrinkled, green.
____ 24. Refer to the illustration above. The genotype represented by the cell labeled “2” is
         a. RRYY.                                          c. RrYy.
         b. RrYY.                                          d. rrYy.
____ 25. Refer to the illustration above. Which of the following cells represents the same phenotype as the cell labeled
         “X”?
         a. “3”                                            c. “5”
         b. “4”                                            d. “6”
____ 26. 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
____ 27. A cross of two individuals for a single contrasting trait is called
         a. monohybrid.                                    c. dominant.
         b. dihybrid.                                      d. codominant.
____ 28. The X and Y chromosomes are called the
         a. extra chromosomes.                             c. sex chromosomes.
         b. phenotypes.                                    d. All of the above
____ 29. Which of the following is the best explanation for the observation that females rarely get the disease
         hemophilia?
         a. Large quantities of male hormones are necessary in order for the gene carrying the disease
             to be expressed.
         b. Female fetuses that carry the gene for the disease die before birth.
         c. A female could only get the disease by having a mother who is a carrier and a father who
             has the disease. Since most males with the disease do not survive to reproductive age, this
             is an extremely unlikely event.
         d. A female could only get the disease by having parents who are both carriers of the disease.
             Because males cannot be carriers, this is an impossible event.
____ 30. In a mating between two parental types, one of which is homozygous dominant for two linked traits and one
         of which is homozygous recessive for the same two linked traits, evidence of crossing-over would be apparent
         in which of the following generations?
         a. parents                                        c. F2
         b. F1                                             d. All of the above
____ 31. A diagram in which several generations of a family and the occurrence of certain genetic characteristics are
         shown is called a
         a. Punnett square.                                c. pedigree.
         b. monohybrid cross.                              d. family karyotype.
____ 32. Which of the following traits is controlled by multiple alleles in humans?
         a. sickle cell anemia                             c. hemophilia
         b. blood type                                      d. pattern baldness
____ 33. Which of the following describes hemophilia?
         a. multiple-allele trait                           c. sex-linked trait
         b. dominant trait                                  d. codominant trait
____ 34. If both parents carry the recessive allele that causes cystic fibrosis, the chance that their child will develop the
         disease is
         a. one in two.                                     c. two in five.
         b. one in four.                                    d. 100 percent.




                                       Figure 12-1

____ 35. Refer to Figure 12-1. If individual III-2 marries a person with the same genotype as individual I-1, what is the
         chance that one of their children will be afflicted with hemophilia?
         a. 0%                                             c. 50%
         b. 25%                                            d. 75%
____ 36. What type of inheritance pattern does the trait represented by the shaded symbols in Figure 12-1 illustrate?
         a. incomplete dominance                           c. codominance
         b. multiple alleles                               d. sex-linked
____ 37. For the trait being followed in the pedigree, individuals II-1 and II-4 in Figure 12-1 can be classified as
         _____.
         a. homozygous dominant                            c. homozygous recessive
         b. mutants                                        d. carriers
____ 38. What is the relationship between individual I-1 and individual III-2 in Figure 12-1?
         a. grandfather-granddaughter                      c. great aunt-nephew
         b. grandmother-grandson                           d. mother-son
____ 39. If a female fruit fly heterozygous for red eyes (XRXr) crossed with a white-eyed male (XrY), what percent of
         their offspring would have white eyes?
         a. 0%                                             c. 50%
         b. 25%                                            d. 75%
____ 40. Which of the bar graphs shown below represents what the phenotypic frequencies might be for polygenic
         inheritance?
         a.                        b.                      c.                       d.
                         Figure 12-3

____ 41. What is the probable mode of inheritance for the normal trait in Figure 12-3?
         a. simple dominant                               c. sex linkage
         b. polygenic                                     d. multiple alleles
____ 42. Based on Figure 12-3, what do you know about individual III-1's mother?
         a. She had the trait.                            c. She was homozygous recessive.
         b. She was a carrier.                            d. She was homozygous dominant.
____ 43. Eye color in humans is the result of _____ inheritance.
         a. multiple allelic                              c. sex-linked
         b. polygenic                                     d. simple dominant
____ 44. Royal hemophilia is the result of _____ inheritance.
         a. multiple allelic                              c. sex-linked
         b. polygenic                                     d. simple dominant
____ 45. The blood types A, B, AB, and O are the result of _____ inheritance.
         a. multiple allelic                              c. sex-linked
         b. polygenic                                     d. simple dominant
____ 46. Two healthy parents produce a child with the genetic disorder of cystic fibrosis, which is the result of a
         recessive gene. What would be the best explanation for this inheritance?
         a. This is not the result of a genetic disorder.
         b. Both parents carried the recessive gene for cystic fibrosis.
         c. Cystic fibrosis is a chromosomal mutation that occurred during development and is not
              related to the parental genotypes.
         d. Cystic fibrosis is caused by a mutation in the 21st pair of chromosomes.
____ 47. A phenotype that results from a dominant allele must have at least _____ dominant allele(s) present in the
         parent(s).
         a. one                                           c. three
         b. two                                           d. four
____ 48. A human genetic disorder caused by a dominant gene is _____.
         a. Tay-Sachs disease                             c. PKU
         b. cystic fibrosis                               d. Huntington's disease
____ 49. A man heterozygous for blood type A marries a woman heterozygous for blood type B. The chance that their
         first child will have type O blood is _____.
         a. 0%                                            c. 50%
         b. 25%                                           d. 75%
____ 50. Sickle-cell anemia is a genetic disease common to human populations from Africa and the Mediterranean
         coast. The incidence is greater in these regions than elsewhere because the heterozygous state provides
         protection against malaria. Individuals afflicted with sickle-cell anemia _____.
         a. are two times more likely to be males than to be females
         b. will not exhibit the symptoms of the disease until around age 40
         c. suffer tissue damage resulting from oxygen deprivation
         d. lack an enzyme that breaks down a lipid produced in the central nervous system
Genetics Practice Test
Answer Section

MULTIPLE CHOICE

      1.   ANS:   C
      2.   ANS:   D
      3.   ANS:   A
      4.   ANS:   A
      5.   ANS:   B
      6.   ANS:   A
      7.   ANS:   B
      8.   ANS:   C
      9.   ANS:   A
     10.   ANS:   B
     11.   ANS:   B
     12.   ANS:   C
     13.   ANS:   A
     14.   ANS:   B
     15.   ANS:   B
     16.   ANS:   A
     17.   ANS:   B
     18.   ANS:   D
     19.   ANS:   B
     20.   ANS:   D
     21.   ANS:   A
     22.   ANS:   D
     23.   ANS:   A
     24.   ANS:   C
     25.   ANS:   D
     26.   ANS:   B
     27.   ANS:   A
     28.   ANS:   C
     29.   ANS:   C
     30.   ANS:   C
     31.   ANS:   C
     32.   ANS:   B
     33.   ANS:   C
     34.   ANS:   B
     35.   ANS:   A
     36.   ANS:   D
     37.   ANS:   D
     38.   ANS:   B
     39.   ANS:   C
     40.   ANS:   A
     41.   ANS:   C
42.   ANS:   B
43.   ANS:   B
44.   ANS:   C
45.   ANS:   A
46.   ANS:   B
47.   ANS:   A
48.   ANS:   D
49.   ANS:   B
50.   ANS:   C