File: ch 14, Chapter 14, Human Genetics

Multiple Choice

1. Dylan has a muscle disorder in which his muscles produce large amounts of an abnormal protein. His mother has a mild version of the disorder as does his brother. If m is the allele for the abnormal protein, and s is the allele for the healthy protein, what are the likely genotypes of Dylan, his mother, and his brother?

a) ms, ss, ss.

b) ss, ms, ms.

c) mm, ss, mm

d) ss, ms, mm.

e) mm, ms, ms

Ans: e

2. Joshua has curly hair and Madison has straight hair, and their child has wavy hair. What pattern of inheritance is likely operative in this family?
a) Dominant.
b) Incomplete dominance.
c) Codominance.
d) Polygenic.
e) Sex-linkage.

Ans: b.

3. Aaliyah has excess fat in the bloodstream, an allele inherited as incomplete dominance. Her father has a more severe form of the disease, and her mother is healthy. What are the likely genotypes of Aaliyah, her father, and her mother?

a) KK’, KK, K’K’.

b) KK, KK’, K’K’.

c) K’K’, KK, KK’.

d) KK’, K’K’, K’K’.

e) KK’, KK, KK.

Ans: a.

4. Olivia, blood type B, had an immune reaction when transfused with blood type A red cells. Her son, blood type AB, had no such reaction when transfused with blood type A red cells. Why?
a) The gene for type A is dominant over the gene for type B.
b) The gene for type A is incompletely dominant over the gene for type B. (c) Both alleles are active in her son.
d) Two gene pairs are active in the son.
e) Blood type genes are sex-linked, so the type B gene is inactive in her son.

Ans: c

5. Sierra, who has the genotype mmRR, suffered from appendicitis. Rick was not afflicted by appendicitis because his genotype was MMrr. How would you describe this mode of inheritance?
a) Autosomal dominant.
b) Autosomal recessive.
c) Incomplete dominance.
d) Codominance
e) Polygenic inheritance.

Ans: e

6. Ashley has cancer and she wondered if it could be passed to her children. Her physician informed her that her genotype of BBCC did increase her susceptibility to cancer. What pattern of inheritance has predisposed her to cancer? This question is confusing because it talks about her inheritance and doesn’t deal with her children.

a) Dominant.
b) Incomplete dominance.
c) Codominance.
d) Polygenic.e) Sex-linkage.

Ans: d.

7. If human skin color is controlled by polygenic inheritance, and maximum pigment production is caused by the additive effects of genes A, B, and C upper-case alleles, what would be the genotype of a person with medium-colored skin?

a) AABBCc

b) AaBbCc

c) aaBBcc

d) aabbcc

e) aABBCc

Ans: b

8. Emily has autosomal dominant disorder for deafness, as did her parents, although her sister has normal hearing. What are possible genotypes of Emily, her mother, father, and sister?

a) DD, Dd, dd, dd.

b) DD, DD, DD, Dd.

c) DD, Dd, dd, Dd.

d) Dd, Dd, Dd, dd.

e) Dd, DD, Dd, dd.

Ans: d.

9. Noah has heart disease and kidney failure due to excessive blood pressure caused by high levels of a blood-pressure-inducing enzyme, ACE (spell out what ACE is here). His father had similar ACE levels but those of his mother are normal. What pattern of inheritance might best explain this situation?

a) Dominant.
b) Incomplete dominance.
c) Codominance.
d) Polygenic.
e) Sex-linkage.

Ans: a

10. Jasmine’s mother has autosomal dominant ovarian cysts. We do not know the mother’s genotype. What is the likely scenario for this disease in Jasmine’s family?

a) Jasmine might not inherit the gene.

b) Jasmine will not develop cysts unless her mother was a homozygote.

c) Jasmine will not develop cysts unless her father also carried the gene.

d) If Jasmine carries the gene it cannot be passed to her son.

e) Jasmine is guaranteed of inheriting the gene.

Ans: a

11. Ethan has healthy parents, but he has autosomal recessive Wilson disease, a disorder in which the body accumulates copper, damaging the liver and nervous system. How might you depict Ethan’s genotype, followed by the genotypes of his father and mother (using letters of the alphabet)?
a) Ww, WW, Ww
b) ww, Ww, Ww.
c) WW, Ww, ww.
d) ww, WW, ww.
e) Ww, Ww, WW

Ans: b

12. Moto has very high blood cholesterol levels caused by an autosomal recessive allele. His parents and sister have normal cholesterol. What are possible genotypes of Moto, his mother, his father, and his sister?

a) cc, Cc, Cc, CC.

b) cc, CC, Cc, Cc.

c) cc, Cc, Cc, cc.

d) Cc, CC, CC, CC.

e) CC, Cc, Cc, CC.

Ans: a

13. Denzel is healthy, but his mother has autosomal recessive knee dislocation. His father is healthy. What is the likely scenario for this disease in Denzel’s family?

a) Only his daughters can get the disease..

b) Only his son can get the disease.

c) His children cannot get the disease unless Denzel’s father was a carrier.

d) His children cannot get the disease unless Denzel’s mate is a carrier.

e) Denzel cannot have inherited the gene for the disorder.

Ans: d

14. Renee had a child that developed difficulty breathing due to cystic fibrosis, an autosomal recessive disorder. The number of white Americans heterozygous for this disease is about one in twenty and the number of homozygotes is about one in 1800. Why the large difference in numbers?a) Cystic fibrosis is caused by a dominant allele.

b) Most heterozygotes die young.

c) It is a recessive disease, and therefore appears only every second generation.

d) The probability of two heterozygotes mating is low.

e) Heterozygotes are likely sterile.

Ans: d

15. Michael has an inherited blood disease most commonly found in those of black African descent How would you best characterize this disorder?

a) A type of hemophilia..

b) A deficiency of a chloride transporter.

c) Fatty acid accumulation.

d) Oxygen deprivation.

e) Excessive hemoglobin production.

Ans: d

16. Alger experienced mental deterioration. What might be a clue that he had Tay-Sachs disease rather than Huntington’s disease?

a) Airway mucus.

b) Early onset.

c) Misshapen blood cells.

d) XO karyotype.

e) Down syndrome.

Ans: b.

17. Carlos has sex-linked recessive muscular dystrophy, as did his father, although his mother is healthy. What are possible genotypes of Carlos, his father, and his mother?

a) mm, mm, Mm.

b) mm, Mm, Mm.

c) Mm, MM, mm.

d) m, m, Mm

e) m, m, MM

Ans: d.

18. Paige has X-linked dominant bone disease, as does her father. Her mother is healthy. What are possible genotypes of Paige, her father, and her mother?

a) Bb, BB, bb.

b) Bb, B, bb.

c) B, BB, Bb.

d) bb, BB, Bb.

e) Bb, bb, BB.

Ans: b

19. Jose has retinosis, a sex-linked recessive eye disorder. What is the likely scenario for this disease in Jose’s family?

a) He can pass it only to his sons.

b) The disease will skip a generation.

c) His daughter cannot get the disease unless her mother has the disease.

d) His son cannot get the disease unless his mother has the disease.

e) His daughter can get the disease even if her mother is healthy.

Ans: e

20. Kevin has X-linked dominant skin-scaliness. What is the likely scenario for this disease in Kevin’s family?

a) He can pass it only to his sons.

b) The disease will skip a generation.

c) His daughter cannot get the disease unless her mother has the disease.

d) His son can get the disease even if his mother is healthy.

e) His daughter can get the disease even if her mother is healthy.

Ans: e

21. In a pedigree showing the inheritance of colorblindness, what would represent the father of a person represented by a solid-colored circle?

a) Partially-colored circle.

b) Unshaded circle.

c) Solid-colored square.

d) Unshaded square.

e) Partially-colored square.

Ans: c

22. If you examine a pedigree for the inheritance of colorblindness, what would represent the daughter of parents depicted by a colored square and an unshaded circle?

a) Partially-colored circle.

b) Unshaded circle.

c) Solid-colored square.

d) Unshaded square.

e) Partially-colored square.

Ans: a

23. Examine the pedigree below. What is the relationship number 7 to number 8?

a) 7 is wife of 8.

b) 7 is husband of 8.

c) 7 is brother of 8.

d) 7 is sister of 8.

e) 7 is daughter of 8.

Ans: d

24. Examine the pedigree below. Only afflicted individuals are shaded. Other genotypes are open to your interpretation. What is the most likely mode of inheritance?

a) Autosomal dominant.

b) Autosomal recessive.

c) X-linked recessive.

d) X-linked dominant.

Ans: b

25. Examine the pedigree below. Shading of which of the following (in addition to those already shaded) would be consistent with sex-linked dominance?

a) 2 and 4.

b) 1, 3 and 9.

c) 2, 3, and 9.

d) 2, 4, and 6.

e) 2, 4, and 7.

Ans: e

26. Examine the pedigree below. What is the LEAST likely mode of inheritance of the trait?

a) Autosomal dominant.

b) Autosomal recessive.

c) Sex-linked recessive.

d) Sex-linked dominant.

Ans: d

27. Sue was told that her baby has Down syndrome and will be mentally handicapped as it had two copies of the same chromosome from its father. Which of the following would be most likely to have caused the Down syndrome?

a) XYY father.

b) Deletion.

c) Amniocentesis.

d) Karyotyping.

e) Nondisjunction.

Ans: e

28. How many chromosomes would be observed  in the body cell of a person whose mother produced an egg cell with two copies of chromosome 21?
a) 21
b) 42
c) 45
d) 47
e) 63

Ans: d

29. Which abnormal sex chromosome pattern might be most likely to be found in a fertile human?
a) XX
b) XY
c) XO
d) XXY
e) XYY

Ans: e

30. Which of the following karyotypes would you LEAST likely expect to observe?

a) XO

b) XXY

c) XXX

d) XYY

e) OY

Ans: e.

31. Sachi and Nicholas both produced gametes resulting from meiotic sex chromosome nondisjunction. If two of these gametes were to fuse, what would be the LEAST likely sex chromosome karyotype of the zygote?

a) Absence of sex chromosomes.

b) XX

c) XY

d) XXY

e) XXXY

Ans: d

32. Which chromosomal abnormality would be most difficultto notice when examining a karyotype?
a) Nondisjunction.
b) Translocation.c) Inversion
d) Trisomy.
e) Duplication.

Ans: c.

33. Mako was a laboratory technician examining a karyotype and she noticed an unusually long chromosome within one chromosome pair. What is the most likely cause of this?

a) Inversion.

b) Deletion.

c) Translocation.

d) Nondisjunction.e) Mutation.

Ans: c

34. Corrine is pregnant and is planning to request a karyotype of her fetus. What might the karyotype be LEAST likely to detect?

a) An inherited disorder caused by a mutation in the DNA.

b) A duplication

c) A translocation.

d) A deletion.

e) An inversion.

Ans: a

35. Leona was considering having her fetus genetically screened and was confused regarding the difference between amniocentesis and chorionic villus sampling (CVS). How would you explain the difference?

a) Amniocentesis examines chromosomes, whereas CVS examines DNA.

b) Amniocentesis is done via the abdomen whereas CVS is done via the vagina.

c) Amniocentesis samples cells whereas CVS samples fluid.

d) Amniocentesis samples the fetus whereas CVS samples a fetal membrane.

e) Amniocentesis is done prior to the fourth month of pregnancy whereas CVS is done later.

Ans: b

Short Answer

36. Could a person with blood type AB be transfused with blood type B red cells? Explain.

Ans: Yes. A person with blood type AB has genes for both type A and type B cell-surface recognition markers, so the immune system regards neither type A cells nor type B cells as foreign.

37. Louise had a child with the autosomal recessive disorder phenylketonuria, known to be caused by an abnormal gene on chromosome number 12. Her neighbor also had a child with the disorder, but in a more severe form. What is a genetic (as opposed to an environmental) explanation for the difference in severity (assuming that the disease is caused by a single gene pair)?

Ans: Likely there are multiple alleles, some causing more severe illness than others.

38. If people from black and white races were to extensively intermarry and produce offspring, would this result in a population with only medium skin color? Explain.

Ans: No. Skin color inheritance is polygenic, the alleles having an additive effect. Two medium-colored people could produce both black and white offspring. AaBbCc + AaBbCc could yield aabbcc or AABBCC, as each parent has one copy of each of the pigment genes (upper case) as well as one copy each of the nonpigment genes.

39. Manako and Sachi were identical twins who lived apart. Sachi suffered from asthma, obesity, and stroke, and genetic typing showed that she had genes predisposing her to these conditions. However, Manako was healthy. Suggest why Manako is healthy and Sachi is not, despite having the same genes.

Ans: Although identical twins share the same genes, the effects of some genes may be present only in certain environments. If Sachi, (but not Manako) smokes, overeats, and is inactive, she may experience asthma, weight gain, high blood pressure, and stroke.

40. Suggest an explanation as to why inherited diseases caused by dominant genes are less common than inherited diseases caused by recessive genes.

Ans: Reproduction resulting in people afflicted with recessive disorders can be via mating of two healthy carriers. Reproduction resulting in people afflicted with dominant disorders must occur via mating of people in whom the gene will be expressed. These people may be ill, may leave few offspring, or may die before reproductive age.

41. Charlotte was told that she is a carrier of the cystic fibrosis gene, a defective chloride secretion gene, an autosomal recessive allele. She was told that healthy carriers of the gene may have superior resistance to cholera and perhaps other diarrheal diseases. How would you explain this situation? Can you think of another similar example?

Ans: This is a heterozygote advantage. The defective gene protects a healthy carrier from a disease, just as sickle cell carriers are protected from malaria.

42. Charlene’s father had late-onset X-linked recessive muscular dystrophy. Charlene was confident that she would be healthy because the disease is sex-linked. Is her confidence justified? Explain.

Ans: No. Her father would have passed the X-linked gene to her, and if by chance her mother was a carrier, Charlene could have received the X-linked gene from her mother, thus making Charlene a homozygote.

43. Rubin has a deficiency of phosphate in his blood, causing weak bones. His father and his father’s father also had this disorder. His mother’s side of the family is healthy. He suspects that the prevalence of disease in males means that it is X-linked? Could he be correct? Explain.

Ans: Unlikely, as the family history of the disease is on his father’s side and the father contributes a Y-chromosome to his son, not an X-chromosome.

44. Marie was 47 years old and wanted a child. She was told that the likelihood that the child would have Down syndrome was very high. What is a biological reason for this high risk?

Ans: The reason may involve the incidence of fertilization of older egg cells. As time goes by, chromosomes within these cells can become unpaired, allowing nondisjunction to occur.