Genetics Quiz 3

Genetics Quiz

Genetics Quiz #3

The basic unit of genetic function is the gene, the chemical basis for which is the DNA molecule. DNA consists of a pair of strands of a sugar-phosphate backbone attached to a set of pyrimidine and purine bases (Fig. 1). The strands are held together by hydrogen bonds between adenine and thymine bases and between guanine and cytosine bases. Together these strands form a double helix. The strands separate during DNA replication, and the base sequence of the newly synthesized strand is dictated by the complementarity of adenine with thymine and guanine with cytosine. DNA, therefore, contains within its structure the information necessary for its replication.

61. Unpredictable, chance fluctuation in allele frequency that has a neutral effect on fitness is called:

  • A) founder effect.
  • B) selection.
  • C) genetic drift.
  • D) mutation.
  • E) inbreeding.
Ans: {C} genetic drift.

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    62. The process in which rare alleles increase in frequency in a new population is known as:

    • A) gene flow.
    • B) genetic drift.
    • C) founder effect.
    • D) inbreeding.
    • E) selection.
    Ans: {C}  founder effect.

    63. Diseases persist because:

    • A) changes in allele frequency tend toward evolutionary equilibrium.
    • B) mutation balances selection.
    • C) the alleles become dominant.
    • D) only a and b.
    • E) a, b, and c.
    Ans: {D} only a and b. 

    64. The factors contributing to the antibiotic resistance of bacterial pathogens are:

    • A) patient noncompliance with drug treatments.
    • B) strong selection imposed by antibiotics increases the rate of evolution in each generation.
    • C) plasmids provide a means for the genetic exchange of resistance genes.
    • D) only b and c.
    • E) a, b and c.
    Ans: {E} a, b and c.

    65. Development of Insulin-dependent diabetes is associated with how many separate regions of the human genome?

    • A) 12
    • B) 10
    • C) 8
    • D) 6
    • E) 4
    Ans: {A} 12

    66. Multifactorial traits:

    • A) are affected by both genetic and environmental factors.
    • B) are continuous.
    • C) vary over a continuous range of measurements.
    • D) are affected by environmental factors such as penetrance and expressivity.
    • E) all of the above.
    Ans: {E} all of the above.

    67. The total phenotype variance (VP) is:

    • A) the sum of genetic variance (VG) and environmental variance (VE).
    • B) the difference between VG and VE.
    • C) not dependent on VG.
    • D) not dependent on VE.
    • E) always constant.
    Ans: {A} the sum of genetic variance (VG) and environmental variance (VE).

    68. Heritability is defined as:

    • A) VG.
    • B) VP.
    • C) VE.
    • D) VG/VP.
    • E) VP/VG.
    Ans: {D} VG/VP.

    69. The total genetic relatedness of two siblings is:

    • A) 2.
    • B) 1.
    • C) 0.5.
    • D) 0.2.
    • E) none of the above.
    Ans: {C} 0.5.

    70. Which of the following is not true about monozygotic twins.

    • A) They share all alleles at all loci.
    • B) They have a genetic relatedness of 0.5.
    • C) They have a genetic relatedness of 1.
    • D) They come from the joining of a single egg with a single sperm cell.
    • E) They are the result of a split of the zygote after fertilization.
    Ans: {B} They have a genetic relatedness of 0.5.

    71. Recent heritability studies on twins show that there is a genetic component to:

    • A) memory.
    • B) extroversion.
    • C) verbal reasoning.
    • D) a, b, and c.
    • E) only a and b.
    Ans: {D}  a, b, and c.

    73. The response to selection, R, is equal to:

    • A) the heritability (h2) of a trait.
    • B) the strength (S) of selection.
    • C) the difference between h2 and S.
    • D) S/h2
    • .E) h2S.
    Ans: {E} h2S. 

    74. A number of interacting genes produce quantitative inheritance. The transmission of these genes can be seen in the phenotypical pattern of:

    • A) discontinuous distribution of discrete phenotypes.
    • B) continuous variation in phenotypic expression.
    • C) strict dominance and recessiveness.
    • D) all of the above.
    • E) only a and b.
    Ans: {B} continuous variation in phenotypic expression.

    75. A cross between a tall and a short pea plant produced intermediate height in the F1 generation. When the F1s were crossed plants of the original parental heights and plants with a range of heights in between the extremes were produced. The mode of inheritance is described as:

    • A) multifactorial.
    • B) independent assortment.
    • C) incomplete dominance.
    • D) codominance.
    • E) segregation.
    Ans: {A} multifactorial.

    76. Multifactorial inheritance is observed in phenotypes which show typically:

    • A) only one discrete type.
    • B) two extremes.
    • C) a bell-shaped distribution.
    • D) a higher mutation rate.
    • E) all of the above.
    Ans: {C} a bell-shaped distribution.

    77. Continuous traits are:

    • A) due to sex-linked genes only.
    • B) due to autosomal genes only.
    • C) qualitative in nature.
    • D) quantifiable in measurements.
    • E) result of test-crosses only.
    Ans: {D} polygenic traits.

    78. In addition to genetic factors, environmental factors influence the inheritance of:

    • A) metabolic diseases.
    • B) recessive diseases.
    • C) dominant diseases.
    • D) sex-linked diseases.
    • E) polygenic traits.
    Ans: {E} polygenic traits.

    79. Brown insects living in a dark background survived in a ratio of 90/120, while the same insects in a lighter background survived in a ratio of 30/120. The ratio of relative fitness of the in sectsin dark to lighter background is:

    • A) 1 : 0.333.
    • B) 0.75 : 0.25.
    • C) 90 : 120.
    • D) 3: 1.
    • E) none of the above.
    Ans: {A} 1 : 0.333.

    80. If the relative fitness of genotypes MM, MN, NN are 0.8, 1.0, and 0.2 respectively, the expected equilibrium frequency of N is:

    • A) 0.8.
    • B) 1.0.
    • C) 0.2.
    • D) 1.25.
    • E) 4.0.
    Ans: {C} 0.2.

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    81. Twins made from two individual zygotes (dizygotic twins):

    • A) are related genetically as the monozygotic twins.
    • B) share 0% genetic similarities.
    • C) are similar in 100% of genetic sequences.
    • D) are related genetically as non-twin siblings.
    • E) is similar to parents.
    Ans: {D}  are related genetically as non-twin siblings.

    82. An increase in fitness is described as:

    • A) migrating to a new environment.
    • B) successful adaptation.
    • C) being successful in producing many offspring.
    • D) exhibiting new traits.
    • E) mutating to a dominant trait.
    Ans: {B} successful adaptation. 

    83. The frequencies of ABO blood groups in a certain population are: A=0.22, B=0.44, AB=0.18, and O=0.16. The frequency of the O allele in the population is:

    • A) 0.469.
    • B) 0.663.
    • C) 0.424.
    • D) 1.0.
    • E) 0.4.
    Ans: {E} 0.4.

    84. Under special circumstances, migration does not change allele frequencies. If the allele frequencies of a dominant and recessive allele are both 0.5, then migration of which of the following will not change the frequencies of the alleles?

    • A) homozygous recessive individuals
    • B) haploid individuals
    • C) diploid individuals
    • D) heterozygous individuals
    • E) homozygous dominant individuals
    Ans: {D} heterozygous individuals 

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