Mendelian Genetics (Chapter 9 (part), Tobin & Duschek; Chapter 12 (part), Audesirk)


1. A ___________ is a portion of DNA that resides at a particular locus or site on a chromosome and encodes a particular function.

2. The region of the chromosome occupied by a gene is called a ____________.


3. Gregor Mendel concluded that each pea has two units for each trait, and each gamete contains one unit. Mendel's "units" are now referred to as _____________.

a. genes

b. characters

c. alleles

d. transcription factors

e. none of the above


4. A __________ is a cross between an individual of unknown genotype and a homozygous recessive.

5. The physical appearance of a character is the _______________ while the genetic constitution is the ______________.

6. When a cross is made and a trait disappears in the F1 generation, only to reappear in the F2, the trait is probably _____________.


7. What is the ratio of phenotypes in the offspring produced by the cross Aa Aa? Assume complete dominance for the trait.

a. 100% dominance

b. 100% recessive

c. 75% dominant: 25% recessive

d. 50% dominant: 50% recessive

e. 25% dominant: 75% recessive



8. If the allele for inflated pea pods (I) is dominant to the allele for constricted (i), the cross Ii ii is expected to produce:

a. All with inflated pods

b. All with constricted pods

c. Half with inflated and half with constricted pods

d. 3/4 with inflated and 1/4 with constricted pods

e. 3/4 with constricted and 1/4 with inflated pods

9. According to the Law of Segregation:

a. Each individual carries a single copy of each "factor."

b. Pairs of factors fuse during the formation of gametes.

c. Pairs of factors separate during the formation of gametes.

d. The sex chromosomes of males and females differ.

e. There is an independent assortment of non-homologous chromosomes during meiosis.

10. According to the Law of Segregation, in an organism with the genotype Aa:

a. All the gametes will have gene A

b. All the gametes will have gene a

c. Half the gametes will have A and half will have a

d. 3/4 of the gametes will have A and 1/4 will have a

e. 1/4 of the gametes will have A and 3/4 will have a

11. A recessive gene is one:

a. That is not expressed as strongly as a dominant allele

b. Whose effect is masked by a dominant allele

c. That appears only in a heterozygote

d. That produces no effect when present in the homozygous condition

e. That must be lethal in the homozygous condition

12. Which of the following statements is false?

a. Individuals with the same phenotype might have different genotypes.

b. Matings between individuals with dominant phenotypes cannot produce offspring with recessive phenotypes.

c. Matings between individuals with recessive phenotypes usually do not produce offspring with dominant phenotypes.

d. Individuals with the same genotype might have different phenotypes.

e. All of the above choices are correct.



13. If, in a heterozygous individual, only one allele is expressed in the phenotype, that allele is:

a. Normal

b. Haploid

c. Potent

d. Recessive

e. Dominant

14. The physical manifestation of an organism's genes is its:

a. Environment

b. Genotype

c. Phenotype

d. Genetic code

e. Number of chromosomes

15. A cross produced 915 offspring with normal pigment and 310 with albinism. Conclusion?

a. One of the parents was homozygous for albinism.

b. Both parents were heterozygous.

c. One parent was homozygous for normal pigmentation.

d. Both parents were albinos.

e. 605 albino zygotes must have failed to develop.

16. When the two gametes that fuse to form a zygote contain different alleles of a given gene, the offspring is:

a. Haploid

b. Heterozygous

c. Abnormal

d. Homozygous

e. A new species

17. If we cross two pea plants each heterozygous for yellow seed color genes, the expected ratio of yellow : green among the offspring will be:

a. 25% yellow : 75% green

b. 50% yellow : 50% green

c. 75% yellow : 25% green

d. 100% yellow

e. 100% green

18. What type of allele produces its effects only in homozygous individuals?

a. Recessive

b. Dominant

c. Incompletely dominant

d. Diploid

e. Haploid


19. When alleles move into different gametes, this demonstrates:

a. Dominance

b. Independent assortment

c. Fertilization

d. Crossing-over

e. Segregation

20. If a round pea has a wrinkled parent, the round pea is:

a. RR

b. Rr

c. rr

d. Haploid

e. Recessive

21. Mendel's Law of Segregation states that:

a. Members of a pair of alleles move away from each other during gamete formation

b. Each gamete receives a full complement of chromosomes

c. There may be alternative forms of the same gene

d. Genes end up in respective gametes by chance

e. Genes in the same chromosome must stay together

22. When Mendel used true-breeding white flowers and true-breeding purple flowers as the parental generation, he obtained the following results:

a. All the offspring had white flowers

b. All the offspring had purple flowers

c. 3/4 of the flowers produced were purple and 1/4 were white

d. 3/4 of the flowers produced were white and 1/4 were purple

e. 1/2 of the flowers produced were white and 1/2 were purple

23. The genetic makeup of an individual is its:

a. Phenotype

b. Sex cells

c. Mutation

d. Gene pool

e. Genotype



24. The results of a testcross reveal that all the offspring resemble the parent being tested. This parent must be:

a. Heterozygous

b. Recessive

c. Self-pollinated

d. Homozygous

e. Haploid

25. A Mendelian testcross is used to determine whether:

a. An allele is dominant or recessive

b. Flowers are purple or white

c. The genotype or phenotype is more important

d. An individual is homozygous or heterozygous

e. Segregation or independent assortment is occurring

26. Yellow-seeded pea plants may be homozygous or heterozygous. To find out which, we can cross the plants with:

a. True-breeding yellow-seeded plants

b. True-breeding green-seeded plants

c. Heterozygous green-seeded plants

d. Heterozygous yellow-seeded plants

e. The same genotype

27. In a testcross, what percentage of the offspring will have the same genotype as the tested parent if the parent is homozygous?

a. 25%

b. 50%

c. 75%

d. 100%

e. 0%

28. What is the genotype of a dominant individual if some of its offspring show the recessive phenotype?

a. DD

b. Dd

c. dd

d. Cannot tell without more information.

e. Either DD or Dd


29. A particular genetic cross in which the individual in question is crossed with an individual known to be homozygous for a recessive trait is referred to as a

a. parental cross.

b. F1 cross.

c. F2 cross.

d. reciprocal cross.

e. test cross.

30. Crossing spherical-seeded pea plants with dented seeded pea plants resulted in progeny that all had spherical seeds. This indicates that the dented seed trait is

a. codominant.

b. dominant.

c. recessive.

d. a and b.

e. a and c.

31. Cleft chin is an autosomal dominant trait. A man with a cleft chin marries a woman with a round chin. What proportion of their female progeny will show the trait?

a. 0%

b. 25%

c. 50%

d. 75%

e. 100%

32. A pea plant with red flowers is test crossed and one half of the resulting progeny have red flowers, while the other half have white flowers. You know that the genotype of the test crossed parent was

a. RR.

b. Rr.

c. rr.

d. either RR or Rr.

e. Cannot tell unless the genotypes of both parents are known.

33. Classical albinism results from a recessive allele. Which of the following is the expected offspring from a normally pigmented male with an albino father and an albino wife?

a. 75% normal; 25% albino

b. 75% albino; 25% normal

c. 50% normal; 50% albino

d. All normal

e. All albino

34. In garden peas, the allele for tall plants is dominant over the allele for short plants. A true-breeding tall plant is crossed with a short plant and one of their offspring is test crossed. Out of 20 offspring resulting from the test cross, about ______________ should be tall.

a. 0

b. 5

c. 10

d. 15

e. 20


MATCHING TEST: Each choice may be used more than once.


a. genotype

b. incomplete dominance

c. heterozygote

d. homozygote

e. phenotype

35. An individual having 2 identical alleles at a particular locus.

36. The outward physical appearance of an individual.

37. The dominant appearance of a Bb individual.

38. The entire genetic constitution of an individual.

39. The Bb individual.

40. A couple who are both carriers for the gene for cystic fibrosis have two children with cystic fibrosis. The probability that their next child will have cystic fibrosis is __________ percent.

41. An individual with two identical alleles of a gene is said to be __________, while with two different alleles for the same gene is said to be __________.

42. The physical appearance of a trait is the __________ and the actual alleles present at the individual's __________.


43. In crossing a homozygous recessive with a heterozygote, what is the chance of getting a homozygous recessive phenotype in the F1 generation?

a. 0%

b. 25%

c. 50%

d. 75%

e. 100%



44. If two parents are carriers of albinism (an autosomal recessive trait), what is the chance that their fourth child will have a homozygous genotype?

a. 0%

b. 25%

c. 50%

d. 75%

e. 100%


45. Why must the genotype always be shown as two alleles?

46. Assuming that albinism is under the control of a single gene pair and inherited as an autosomal recessive trait, could two albino individuals ever produce any offspring with normal pigmentation?

47. If A is dominant to a. In the cross between Aa aa, what percentage of individuals will have the A phenotype?

48. The independent inheritance of two or more distinct traits is called the _______________________.

49. What is a physical requirement in order for independent assortment of alleles for two different genes to occur?

50. Describe where in the process of meiosis independent assortment of genes occur.


51. Although the law of independent assortment is generally applicable, when two loci are on the same chromosome the phenotypes of the progeny sometimes do not fit the phenotypes predicted. This is due to

a. translation.

b. inversions.

c. chromatid abnormalities.

d. linkage.

e. reciprocal chromosome exchange.


52. Describe a reason for when the pattern of inheritance breaks the law of independent assortment.

53. What occurs to result in linked genes not being inherited together?



54. All of the following combinations are possible in the gametes of an organism that is AaBb except:

a. AB

b. aB

c. aa

d. ab

e. Ab






1. gene

2. locus


3. a


4. test cross

5. phenotype; genotype

6. recessive


7. c

8. c

9. c

10. c

11. b

12. b

13. e

14. c

15. b

16. b

17. c

18. a

19. e

20. b

21. a

22. b

23. e


24. d

25. d

26. b

27. d

28. b

29. e

30. c

31. e

32. b

33. c

34. c


35. a

36. e

37. e

38. a

39. c

40. 25

41. homozygous; heterozygous

42. phenotype; genotype


43. c

44. c


45. Because each individual inherits two allelles for a gene, one from the maternal gamete and the other from the paternal gamete.

46. No, since albinism is an autosomal recessive trait both parents will be homozygous recessive.

47. 50%

48. Law of Independent Assortment

49. Genes must be on different chromosomes.

50. Homologous pairs of chromosomes align randomly along the metaphase plate during metaphase I.


51. d


52. In the case of linked genes

53. Recombination of chromosomes during cross over during Prophase I.


54. c