Patterns of Inheritance Practice Problems

By — McGraw-Hill Professional
Updated on Aug 19, 2011

Review the following concepts if needed:


    Matching Questions I     In guinea pigs, black coat color is dominant over white. Match the correct answer in the right column with the question in the left column.

    Matching Questions II     In guinea pigs, black (B-) is dominant to white (bb). Assorting independently on a different pair of homologues, short hair (S-) is dominant to long hair (ss). In the parental generation, pure (homozygous) black, short-haired pigs are crossed to white, long-haired pigs. In the F2 we expect the following:

    Vocabulary   For each of the following definitions, give the appropriate term and spell it correctly. Terms are single words unless indicated otherwise.

    1. Any measurable or distinctive characteristic or trait possessed by an organism.
    2. The genetic endowment of an individual or cell.
    3. A cell produced by the union of gametes carrying identical alleles.
    4. A cell produced by the union of gametes carrying different alleles.
    5. Adjective descriptive of an allele that is not expressed in a heterozygote; also descriptive of the phenotype produced when the allele is homozygous.
    6. Any phenotype that is extremely rare in a natural population. (One or two words.)
    7. Adjective describing any pair of alleles that interact in the heterozygous condition to produce a phenotype different from those of the respective homozygotes. (One or two words.)
    8. Any gene that when homozygous results in the death of the individual during development.
    9. The proportion of individuals of a specified genotype that show the expected phenotype.
    10. The degree of effect produced by a given genotype under a given set of environmental conditions or over a range of environmental conditions.

    Multiple-Choice Questions   Choose the one best answer.

    Questions 1–5 use the following information. In guinea pigs, black coat color (governed by gene B) is a dominant trait, and white (attributed to allele b) is a recessive trait.

    1. A black female is testcrossed, producing six black offspring. The probability that a heterozygous black female would do this by chance alone is approximately   (k) 50%   (l) 25%   (m) 1%   (n) cannot be determined from the information given   (o) none of the above
    2. A mating that is expected to produce 50% homozygotes and 50% heterozygotes is   (a) BB × Bb   (b) Bb × Bb   (c) bb × Bb   (d) two of the above   (e) matings (a), (b), and (c) above
    3. When heterozygous black pigs are intercrossed, approximately what fraction of the black progeny are expected to be homozygous?   (a) 4   (b) 2/3   (c) 2   (d) 3   (e) none of the above
    4. How many genetically different kinds of matings can be made in a population containing these two alleles (ignoring reciprocal crosses)?   (a) 4   (b) 6   (c) 8   (d) more than 8   (e) none of the above
    5. When heterozygous black pigs are intercrossed the chance of the first two offspring being black is   (a) more than 75%   (b) 56%   (c) 44%   (d) 6%   (e) none of the above
    6. The ABO blood groups of humans are determined by three alleles (Example 2.19). How many genotypes are possible for these phenotypes?   (a) 3   (b) 4   (c) 6   (d) 8   (e) none of the above
    7. A mother of blood group O has a group O child. The father could be   (a) A or B or O   (b) O only   (c) A or B   (d) AB only   (e) none of the above
    8. How many different genotypes can exist in a population with the dominance hierarchy ga > gb > gc > gd?   (a) 6   (b) 8   (c) 16   (d) more than 16   (e) none of the above
    9. If an individual of genotype AaBbCcDd is testcrossed, how many different phenotypes can appear in the progeny?   (a) 4   (b) 8   (c) 12   (d) 16   (e) none of the above
    10. If individuals of genotype AaBbCc are intercrossed, how many different phenotypes can appear in their offspring?   (a) 3   (b) 6   (c) 8   (d) 16   (e) none of the above
    11. If individuals of genotype AaBbCc are intercrossed, how many different genotypes can occur in their progeny?   (a) 6   (b) 8   (c) 16   (d) 21   (e) none of the above
    12. The minimum progeny population size allowing for random union of all kinds of gametes from AaBbCc parents is   (a) 9   (b) 27   (c) 64   (d) more than 100   (e) none of the above
    13. Questions 13 and 14 use the following information. Given that A1A1 = lethal, A1A2 = gray, A2A2 = black, B1B1 = long hair, B1B2 = short hair, B2B2 = very short hair (fuzzy), and parents that are A1A2B1B2:

    14. The fraction of the adult offspring that is expected to be gray, fuzzy is   (a) 1/4   (b) 1/2   (c) 2/3   (d) 3/4   (e) none of the above
    15. If fuzzy is lethal shortly after birth, the fraction of the adult progeny expected to be black, short is   (a) 1/4   (b) 1/3   (c) 1/2   (d) 2/3   (e) none of the above


    Matching Questions I

    1. F   2. C   3. A   4. H   5. B   6. D   7. G   8. E

    Matching Questions II

    1. H   2. C   3. C   4. A   5. F   6. A   7. B   8. B


    1. phenotype
    2. genotype
    3. heterozygote (heterozygous cell)
    4. homozygote (homozygous cell)
    5. recessive
    6. mutant type
    7. codominant, incompletely dominant, partially dominant, semidominant
    8. lethal gene
    9. penetrance
    10. expressivity

    Multiple-Choice Questions

    1. c
    2. e
    3. d
    4. b
    5. b
    6. c
    7. a
    8. e (10 genotypes)
    9. d
    10. c
    11. e (27)
    12. c
    13. e (1/6)
    14. e (2/9)
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