Practice problems

25. A male Manx cat and a female Manx cat produce kitten. What is the probability that kitten has a non-manx tail? A. 1/3 B. 1/2 C. 1/4 D. 2/3

A. 1/3

97. In a given mapping experiment, you expect that incidence of double crossovers is 3.5%, but you only observe 2.5%. This can be explained by ________________. A. Interference B. Linkage C. Coincidence D. Segregation

A. Interference

95. In a mapping experiment with three linked genes, which phenotype should occur most often in the F2 offspring? A. Parental phenotypes B. Phenotypes of individuals with single crossover events C. Phenotypes of individuals with double crossover events D. All of the phenotypes should occur equally in the F2 generation

A. Parental phenotypes

50. In the Igf2 gene, which allele is imprinted? Which is expressed? A. Paternal, paternal B. Paternal, maternal C. Maternal, paternal D. Maternal, maternal

A. Paternal, paternal

32. Which of the following could NOT be used to describe a sex limited trait: A. This term refers to a trait controlled by a gene located on the X or Y chromosomes. B. This is a trait that occurs more frequently in one sex than another. C. This is an extreme example of a sex influenced trait. D. This trait is likely to be a secondary sex characteristic.

A. This term refers to a trait controlled by a gene located on the X or Y chromosomes.

58. The Lyon hypothesis attempts to explain the molecular mechanism of _____. A. X-inactivation B. genomic imprinting C. maternal inheritance D. extranuclear inheritance

A. X-inactivation

46. What genes appear to be controlled by the Xic? A. Xist and Tsix B. Xist only C. Tsix only D. None of these

A. Xist and Tsix

67. The inheritance patterns of genetic material that is not contained in the nucleus of the cell is called _______. A. extranuclear inheritance B. maternal effect C. imprinting D. nuclear E. epigenetic

A. extranuclear inheritance

69. If the sperm cell contributes mitochondria to the oocyte, it is called _______. A. paternal leakage B. maternal leakage C. paternal inheritance D. mitochondria E. imprinting

A. paternal leakage

101. Two genes that are located on the same chromosome are said to be _______. A. physically linked B. recombinant C. parental-like D. nonparental-like

A. physically linked

56. How many Barr bodies would an individual with a XXY genotype possess? A. 0 B. 1 C. 2 D. None of the answers are correct

B. 1

98. You have calculated the interference value for a given mapping experiment to be 30%. What does this mean? A. 30% more double crossovers occurred than expected B. 30% fewer double crossovers occurred than expected C. 70% more double crossovers occurred than expected D. 70% fewer double crossovers occurred than expected

B. 30% fewer double crossovers occurred than expected

29.What are the possible offspring from a type A mother and a type AB father? A. A, B, AB, and O B. A, B, and AB C. A and AB D. A only

B. A, B, and AB

78. You develop an inbred strain of mice that display one of two distinct syndromes. What evidence might lead you to believe that these mice are mutant for a gene or genes affected by imprinting? A. The two syndromes occur randomly in the colony of mice. B. All mice of the same litter have the same syndrome. C. All mice have the same syndrome as their mother. D. All mice have the same syndrome as their father.

B. All mice of the same litter have the same syndrome.

45. Who originally identified a highly condensed structure in the interphase of nuclei? A. Lyon B. Barr C. Ohno D. None of the answers are correct

B. Barr

72. Which of the following statements regarding epigenetic inheritance is FALSE? A. Epigenetic inheritance can be reset during gametogenesis. B. Epigenetic inheritance can temporarily affect an individual. C. Epigenetic inheritance does not involve a change in DNA sequence. D. A and C. E. None of the above.

B. Epigenetic inheritance can temporarily affect an individual.

80. Both X-linked genes and extranuclear inheritance produce different results in reciprocal crosses. How can you distinguish between them? A. Extranuclear traits can be transmitted from an unaffected mother to an affected son. B. Extranuclear traits can be transmitted from an affected mother to an affected offspring. C. Extranuclear traits cannot be transmitted from father to son. D. None of these.

B. Extranuclear traits can be transmitted from an affected mother to an affected offspring.

92. Crossing over is more likely to occur between genes that are ______ on a chromosome. A. Close together B. Far apart

B. Far apart

59. Monoallelic expression is associated with which of the following? A. X-inactivation B. Genomic imprinting C. Maternal inheritance D. Extranuclear inheritance

B. Genomic imprinting

60. Differentially methylated domains (DMDs) are associated with which of the following? A. X-inactivation B. Genomic imprinting C. Maternal inheritance D. Extranuclear inheritance E. All of the answers are correct

B. Genomic imprinting

30. In soybeans, resistance to sudden death syndrome (SDS) is inherited as a dominant condition. In some cases, individuals that are not resistant to SDS (but whose parents were) can pass the trait on to their progeny. This is an example of which of the following? A. Overdominance B. Incomplete penetrance C. Incomplete dominance D. Variable expressivity

B. Incomplete penetrance

61. Which of the following is false regarding the mammalian mitochondrial genome? A. It is around 17,000 bp in length B. It is a linear chromosome C. Multiple copies exist in each mitochondria D. It mostly contains rRNA and tRNA genes

B. It is a linear chromosome

53. Where is extranuclear DNA located in mammalian cells? A. Endoplasmic reticulum B. Mitochondria C. Ribosome D. Plasma membrane

B. Mitochondria

81. For a trait known to be caused by a mitochondrial gene variant, there may be an occasional female that can transmit different phenotypes to her progeny on an apparently random basis. What situation might you suspect? A. She is heterozygous for this trait. B. She displays heteroplasmy for this trait. C. She displays a low rate of mutation. D. She is the product of a somatic mutation.

B. She displays heteroplasmy for this trait.

82. Mitochondrial mutations in humans tend to affect some tissues more than others. Which is the most likely explanation? A. Some human tissues do not have mitochondria. B. Some human tissues have higher energy demands than others. C. Some human tissues can synthesize large amounts of ATP in the absence of mitochondrial function. D. Heteroplasmy and subsequent segregation often leads to a variegated phenotype.

B. Some human tissues have higher energy demands than others.

76. A mouse heterozygous at the Igf2 locus is dwarf and has 50% dwarf progeny when mated to a homozygous Igf2- animal. Which statement about this animal is FALSE? A. This mouse must be a male. B. The Igf2- allele in this mouse came from its mother. C. This mouse expresses abnormal Igf-2 protein. D. None of these (all statements are true).

B. The Igf2- allele in this mouse came from its mother.

91. In a chi-square test to determine if two genes are linked or assorting independently, what is the default (null) hypothesis that is tested? A. The genes are linked to one another B. The genes are assorting independently C. The genes are located on the sex chromosomes D. No crossing over occurs E. The distance between the genes is very small

B. The genes are assorting independently

28. You find a pink geranium in your flowerbed of red geraniums. Seeds from self fertilization of this plant produce ¼ red plants, ½ pink plants, and ¼ white plants. When considering the visible phenotype, which explanation is most likely? A. The soil in which the pink plant was growing was deficient in a critical nutrient. B. The pink plant had a new mutation, creating an allele to which the wild type "red" is incompletely dominant. C. The pink plant had a new mutation, creating an allele which is incompletely dominant to red. D. The pink plant had a new mutation, creating an allele which is codominant to "red".

B. The pink plant had a new mutation, creating an allele to which the wild type "red" is incompletely dominant.

71. Which of the following statements about nurse cells are true? A. They are haploid. B. They are able to express both alleles present in the female. C. They are precursors of the embryo. D. Both A and B. E. None of the above.

B. They are able to express both alleles present in the female.

27. Which of the following is the best example of overdominance? A. Two lines of true breeding white parents produce purple flowered offspring. B. Two lines of true breeding tomatoes that are susceptible to verticillium wilt (a fungal infection) produce offspring that are resistant to verticillium wilt. C. Two true breeding lines, one tall and one short, produce offspring of medium height. D. Two true breeding lines, one tall and one short, produce all tall offspring.

B. Two lines of true breeding tomatoes that are susceptible to verticillium wilt (a fungal infection) produce offspring that are resistant to verticillium wilt.

57. The coat color of calico cats is a result of _____. A. maternal inheritance B. X-inactivation C. imprinting D. extranuclear inheritance

B. X-inactivation

48. What gene is most responsible for X-inactivation? A. Xic B. Xist C. Tsix D. Xce

B. Xist

64. In maternal effect, the _______ of the mother determines the _______ of the offspring. A. phenotype, genotype B. genotype, phenotype C. rRNA, tRNA D. imprinting, genotype

B. genotype, phenotype

63. The inheritance of leaf pigmentation in the four-o'clock plant Mirabilis jalapa is an example of ____. A. maternal effect B. maternal inheritance C. epigenetic inheritance D. imprinting

B. maternal inheritance

10. If an allele is dominant in one sex and recessive in another, it is an example of ___________. A. sex-limited inheritance B. sex-influenced inheritance C. incomplete dominance D. simple Mendelian inheritance

B. sex-influenced inheritance

13. Epistasis is _______________. A. another term for overdominance B. when one gene can mask the expression of a second gene C. trait that is only expressed in one sex of the species D. when two dominant alleles can be expressed in the same individual E. None of the answers are correct

B. when one gene can mask the expression of a second gene

55. Which inheritance pattern is common to oogenesis, spermatogenesis, and embryogenesis? A.Maternal inheritance B.Epigenetic inheritance C.Maternal effect D.Paternal inheritance

B.Epigenetic inheritance

100. In humans, there are _______ autosomal linkage groups, plus an X and Y chromosome linkage group. A. 23 B. 46 C. 22 D. 92

C. 22

94. A map distance of 23.6 between two genes indicates which of the following? A. The genes are 23.6 millimeters apart B. There are 23.6 other genes between the two genes of interest C. 23.6% of the offspring exhibit recombination between the two genes D. 23.6% of the offspring do not survive

C. 23.6% of the offspring exhibit recombination between the two genes

33. Which of the following events is LEAST likely to occur in a cross involving epistasis by both genes? A. A monohybrid has a different phenotype from either of the two parents. B. Two lines of true breeding white parents produce purple flowered offspring. C. A 9:3:3:1 ratio of F2 phenotypes is seen. D. All of these are likely to be seen in epistatic interactions.

C. A 9:3:3:1 ratio of F2 phenotypes is seen.

12. A woman who is heterozygous for an allele that results in X-linked pattern baldness marries a man who is nonbald. Which of the following would be true of their offspring? A. All would be bald B. All of the females would be nonbald, all males would be bald C. All of the females would be nonbald, ½ of the males would be bald D. ½ of females would be bald, and ½ of the males would be bald E. All would be nonbald

C. All of the females would be nonbald, ½ of the males would be bald

24. The presence of a group of antigens that determine blood type is an example of a(n) ___________. A. semilethal allele B. sex-linked trait C. multiple allele system D. incomplete dominance

C. Multiple allele system

43. Which of the following is primarily responsible for the maternal effect? A. Sperm cells B. Oocytes C. Nurse cells D. Placenta

C. Nurse cells

75. Monoallelic expression of a gene: A. Occurs when one copy of the gene has been deleted. B. Occurs when one copy of the gene carries a mutation. C. Occurs when the gene is imprinted. D. Is not seen in mammals.

C. Occurs when the gene is imprinted.

96. The middle gene of a three gene mapping experiment can be determined by examining the genotypes of which of the following? A. Offspring that resemble the parents B. Offspring that exhibit a single crossover event C. Offspring that exhibit double crossover events D. None of the answers are correct

C. Offspring that exhibit double crossover events

8. If a geneticist describes a trait as being 70% penetrant, what would they mean? A. Individuals with the trait show variation in expression B. It is lethal in 30% of the individuals who have the trait C. Only 70% of the individuals who carry the allele(s) for a trait express the trait D. The trait is present in 70% of the population

C. Only 70% of the individuals who carry the allele(s) for a trait express the trait

37. You set up a cross between true breeding wild type male fruit flies and true breeding female flies with a yellow body color. You notice in the F1 generation that half the flies, specifically all the males, have yellow body color while the females are wild type (gray). Which of the following explanations is the most likely? A. Some of your females had already mated with yellow males before you collected them. B. Some of your parental flies must have had a new mutation in their germ cells. C. The mutation which causes yellow body color is on the X chromosome. D. The mutation which causes yellow body color is on the Y chromosome.

C. The mutation which causes yellow body color is on the X chromosome.

74. Which of the following statements regarding X inactivation in mammals is FALSE? A. The process is entirely random. B. X inactivation may occasionally occur in males. C. This process ensures a homogenous phenotype in heterozygotes. D. X inactivation occurs early in embryonic development.

C. This process ensures a homogenous phenotype in heterozygotes.

47. Expression of ______ would inhibit X-inactivation. A. Xic B. Xist C. Tsix D. All of the answers are correct E. None of the answers are correct

C. Tsix

9. Phenylketonuria in humans is an example of __________. A. incomplete penetrance B. codominance C. an environmentally-influenced trait D. incomplete dominance

C. an environmentally-influenced trait

68. Heteroplasmy is associated with inheritance patterns involving A. nuclear. B. paternal DNA. C. chloroplasts. D. ribosomes. E. imprinted.

C. chloroplasts.

5. Humans homozygous for the sickle cell allele have sickle cell anemia. A human that is heterozygous for the sickle cell allele is an example of _____________. A. codominance B. incomplete penetrance C. heterozygous advantage D. multiple allele systems

C. heterozygous advantage

7. An individual carries the allele for polydactyly, but is normal. This is an example of __________. A. simple Mendelian inheritance B. incomplete dominance C. incomplete penetrance D. codominance E. gene dosage

C. incomplete penetrance

44. In the gene that affects snail coiling, the ______ is responsible for the phenotype of the offspring. A. mother's phenotype B. father's phenotype C. mother's genotype D. father's genotype

C. mother's genotype

4. For a certain trait, a heterozygous individual has a selective advantage as compared to a homozygous dominant or homozygous recessive individual. This is called ________. A. codominance B. incomplete dominance C. overdominance D. incomplete penetrance E. multiple allele systems

C. overdominance

66. Dosage compensation offsets the problems associated with differences in the number of _______ chromosomes in many species. A. cytoplasmic B. autosome C. sex D. extranuclear E. mitochondrial

C. sex

17. A _______ allele encodes a protein that is made in the proper amount and functions normally. A. loss-of-function B. mutant C. wild-type D. gain-of-function E. lethal

C. wild-type

93. While mapping two genes in Drosophila, you observe 30 recombinants among 200 total offspring. What is the distance between these genes? A. 30 map units B. 6.67 map units C. 200 map units D. 15 map units

D. 15 map units

77. Imprinted genes: A. Provide an example of epigenetic inheritance. B. Are near differentially methylated regions. C. Are only transmitted by one parent. D. A and B E. None of the above.

D. A and B

36. How could you verify that a gene you suspect to be X linked is actually located on the X chromosome? A. Set up reciprocal crosses. B. Set up a two point test cross with another gene known to be located on the X. C. Set up crosses between the F1 and both parental types. D. A and B only. E. None of the above.

D. A and B only.

73. In dosage compensation: A. An X chromosome can be inactivated. B. Gene expression can be increased from a single X chromosome. C. Gene expression can be reduced from a pair of X chromosomes. D. All of the above. E. None of the above

D. All of the above.

3. At the molecular level, type A and type B blood differ in which of the following characteristics? A. The antigens present on the surface of the red blood cells B. The type of sugar found in each type C. The antibodies that are generated against the other type of blood D. All of the answers are correct

D. All of the answers are correct

90. Which of the following statistical tests is used to determine if two genes are linked or assorting independently? A. Sum rule B. Binomial expansion C. Product rule D. Chi-square test

D. Chi-square test

26. In a rare blood type referred to as the Bombay phenotype, individuals are unable to attach the A or B antigens to their red blood cells. Individuals that are homozygous recessive for gene "H" have the Bombay phenotype and their blood type is type "O" regardless of their ABO genotype. This is an example of what extension of Mendelian inheritance? A. Multiple alleles B. Overdominance C. Environmental influence D. Epistasis

D. Epistasis

79. A pattern of transmission where all offspring have the same phenotype as their mother is consistent with which type of non-Mendelian inheritance? A. Maternal effect. B. Genomic imprinting. C. Dosage compensation. D. Extranuclear inheritance.

D. Extranuclear inheritance.

99. Which of the following is not one of the principles of linkage that Morgan obtained from his experiments? A. Genes that are on the same chromosome may be inherited together. B. Crossing over exchanges pieces of chromosomes and creates new allele combinations. C. The likelihood of crossing over occurring between two genes is dependent on the distance of the genes from one another. D. Genes that are on the same chromosome are always transmitted together as a unit.

D. Genes that are on the same chromosome are always transmitted together as a unit.

70. Which of the following is NOT true of a maternal effect gene? A. It is located in the nuclear DNA. B. Maternal genotype affects offspring phenotype. C. It may control deposition of material into oocytes. D. It must be located on the X chromosome.

D. It must be located on the X chromosome.

54. What type of inheritance is observed with extranuclear DNA? A. Mendelian inheritance B. Sex-linked inheritance C. Paternal inheritance D. Maternal inheritance E. Maternal effect

D. Maternal inheritance

51. What is the primary molecular mechanism for imprinting a gene? A. Acetylation B. Nitration C. Phosphorylation D. Methylation

D. Methylation

52. In which cells do erasure and re-establishment of imprinting marks typically NOT occur? A. Nurse cells B. Sperm cells C. Oocytes D. Somatic cells

D. Somatic cells

15. Which of the following is not correct concerning epistatic interactions? A. They can be associated with enzymatic pathways. B. They produce variations in the expected 9:3:3:1 ratio of a dihybrid cross. C. They can result when a gene at one locus masks the expression of a gene at a different locus. D. They always result in a 9:7 ratio of a dihybrid cross. E. They are due to gene interactions.

D. They always result in a 9:7 ratio of a dihybrid cross.

31. In a group of fruit flies homozygous for an allele that causes a reduced number of thoracic bristles, you notice that the number of bristles varies from about half the normal number to only a few bristles. This is an example of which of the following? A. Incomplete dominance B. Overdominance C. Incomplete penetrance D. Variable expressivity

D. Variable expressivity

65. A modification that occurs to a nuclear gene that alters gene expression without modifying the DNA sequence is called _______ inheritance. A. extranuclear B. cytoplasmic C. maternal effect D. epigenetic E. nuclear

D. epigenetic

18. In cattle, the presence or absence of scurs follows a sex-influenced pattern of inheritance. A heterozygous male has _______ and a heterozygous female has _______ . A. Y-linked, X-linked B. no scurs, scurs C. X-linked, Y-linked D. scurs, no scurs

D. scurs, no scurs

88. Which of the following defines the principle of linkage? A. Two or more genes that are physically connected on a chromosome B. Genes that are transmitted to the next generation as a group C. The process by which genetic information is exchanged between homologous chromosomes D. All of the answers are correct E. Both two or more genes that are physically connected on a chromosome and genes that are transmitted to the next generation as a group

E

2. An individual with type A blood and an individual with type B blood mate and have offspring. What blood type is not possible in their offspring? A. Type O blood B. Type A blood C. Type B blood D. Type AB blood E. All blood types are possible

E. All blood types are possible

6. At the molecular level, which of the following best explain heterozygous advantage and overdominance? A. A heterozygous individual can produce more varieties of homodimer proteins B. The alleles produce two different proteins with slightly different functions C. The proteins produced by the alleles may provide a broader range of environmental tolerance, such as temperature ranges D. Infectious organisms may recognize only a specific functional protein E. All of the answers are possibilities

E. All of the answers are possibilities

89. Assume that genes C and D are located on the same chromosome. On one chromosome, alleles C and D are found, while the homologue contains alleles c and d. Which of the following would be evidence of a recombination event? A. Alleles C and D together on one chromosome B. Alleles c and d together on one chromosome C. Alleles C and d together on one chromosome D. Alleles c and D together on one chromosome E. Both alleles C and d together on one chromosome and alleles c and D together on one chromosome

E. Both alleles C and d together on one chromosome and alleles c and D together on one chromosome

14. In a dihybrid cross of two heterozygous individuals, you expect a 9:3:3:1 phenotypic ratio in the offspring, but observe a ratio of 9:7. What is the most likely explanation? A. Codominance B. It is a sex-limited trait C. Simple Mendelian inheritance D. Incomplete penetrance E. Epistatic interaction of the two genes

E. Epistatic interaction of the two genes

16. The multiple effects of a single gene on the phenotype of an organism is called _______. A. epistasis B. penetrance C. expressivity D. overdominance E. pleiotropy

E. pleiotropy

11. Male-pattern baldness is only an autosomal dominant trait in humans. A. True B. False

F

19. In an epistatic interaction, the genes must be located on the same chromosome. A. True B. False

F

34. Sex limited inheritance refers to traits that are located on the X or Y chromosome. A. True B. False

F

35. Incomplete penetrance indicates that individuals who possess a dominant trait always express the trait. A. True B. False

F

38. The best way to identify an X-linked trait in fruit flies is that the trait affects one sex more often than the other. A. True B. False

F

62. mtDNA contains all of the genes necessary for the complete function of mitochondrial metabolism. A. True B. False

F

87. The mitochondrial genome encodes all proteins required to carry out oxidative phosphorylation. A. True B. False

F

102. A negative interference value indicates that the first crossover event enhanced the occurrence of additional crossover events in the region. A. True B. False

T

21. Incomplete dominance is an example of blending of phenotypes, not genotypes. A. True B. False

T

22. Human blood groups are determined by antigens on the surface of red blood cells. A. True B. False

T

23. Variable expressivity means that the phenotype of a trait can vary between individuals. A. True B. False

T

35. For genes which have multiple alleles, the relationships between those alleles can be a variety of types of dominant/recessive relationships. A. True B. False

T

39. Genes on the X or Y chromosomes in humans are not always inherited in a different pattern than are genes on the autosomes. A. True B. False

T

84. Gene products produced by nurse cells are controlled by both alleles of the female. A. True B. False

T

85. Dosage compensation is not required for all X linked genes in mammals. A. True B. False

T

86. Genomic imprinting is an example of epigenetic inheritance. A. True B. False

T

1. In human blood groups, the fact that an individual can have an AB blood type is an example of ___________. A. incomplete dominance B. incomplete penetrance C. sex-influenced trait D. temperature-sensitive conditional allele E. codominance

codominance

20. Typically, a recessive allele increases the expression of a functional protein. A. True B. False

f

49. Both parents usually imprint the same gene. A. True B. False

f

83. In maternal effect inheritance, the phenotype of the mother determines the genotype of the offspring. A. True B. False

f