Genetics Chapter 6

8. Which of the following is not a characteristic of X-linked recessive traits in humans? a. More males than females affected. b. Approximately one-half of the sons of a female carrier are affected. c. They cannot be passed from father to son. d. Phenotypically normal daughters of affected men are always carriers. e. Affected daughters always have an affected mother.

e. Affected daughters always have an affected mother.

19. If the characteristic followed in the pedigree is X-linked recessive allele, what is III-1's genotype? a. Hemizygous for a dominant allele b. Hemizygous for a recessive allele c. Definitely heterozygous d. Definitely homozygous dominant e. Either heterozygous or homozygous dominant

a. Hemizygous for a dominant allele

17. Could the characteristics followed in the pedigree be caused by an X-linked recessive allele? a. Yes, all individuals fit the X-linked recessive inheritance pattern. b. No, the offspring of I-1 and I-2 contradict an X-linked recessive inheritance. c. No, the offspring of I-3 and I-4 contradict an X-linked recessive inheritance. d. No, the offspring of II-3 and II-4 contradict an X-linked recessive inheritance. e. Possibly, but I-4 would have to be a heterozygous carrier if there is X-linked inheritance.

a. Yes, all individuals fit the X-linked recessive inheritance pattern.

38. This is a form of prenatal testing that is most commonly performed between the 15th and 18th week of pregnancy. a. Chorionic villus sampling b. Preimplantation genetic analysis c. Amniocentesis d. Heterozygote screening e. Presymptomatic screening

c. Amniocentesis

16. If the pedigree is for an autosomal recessive characteristic, which individuals are definitely heterozygous? a. I-1, I-2, II-2, II-4, and II-5 b. I-1, I-2, I-4, III-1 c. I-1, I-2, II-4, II-5, III-1 d. II-2, II-4, II-5, II-3 e. II-2, II-4, II-5, III-1

c. I-1, I-2, II-4, II-5, III-1

2. Which of the following descriptions of a Y-linked trait in humans is correct? a. All the sons of an affected father will be affected with the trait. b. Half the sons of a mother whose father was affected with the trait will be affected. c. Half the sons of an affected father will not be affected with the trait and the other half will be infertile. d. All the daughters of an affected father will be phenotypically normal themselves but half of their own sons will be affected with the trait. e. The parents of an affected man likely were both phenotypically normal.

a. All the sons of an affected father will be affected with the trait.

10. Most pedigrees showing the hypothetical human trait show the following characteristics • If a phenotypically normal woman with an affected father has children with an unaffected man, half of the sons and none of the daughters are affected. • Affected females always have an affected father and an affected maternal grandfather. • The trait is never passed from father to son. What is the most likely mode of inheritance for this disorder? a. Autosomal recessive b. Autosomal dominant c. X-linked recessive d. X-linked dominant e. Y-linked

a. Autosomal recessive

9. Most pedigrees showing the hypothetical human trait show the following characteristics • Males and females are equally affected. • Two unaffected parents can have an affected child. • In families in which the parents are unaffected but the children are affected, 1/4 of the children are affected. What is the most likely mode of inheritance for this disorder? a. Autosomal recessive b. Autosomal dominant c. X-linked recessive d. X-linked dominant e. Y-linked

a. Autosomal recessive

20. What is/are the possible inheritance pattern(s) for the characteristic in Pedigree 1? Assume no new mutations and complete penetrance. a. Autosomal recessive only b. Autosomal dominant only c. X-linked recessive only d. X-linked dominant only e. All of the above are possible.

a. Autosomal recessive only

39. This is a form of prenatal testing that is most commonly performed between the 10th and 12th week of pregnancy and involves the insertion of a soft plastic into the vagina to obtain cells. a. Chorionic villus sampling b. Preimplantation genetic analysis c. Amniocentesis d. Heterozygote screening e. Presymptomatic screening

a. Chorionic villus sampling

6. Which term refers to mating between closely related people? a. Consanguinity b. Probanding c. Congenital d. Concordance e. Discordance

a. Consanguinity

5. In pedigree analysis, the proband is a. the individual having the trait or disorder from whom the pedigree is initiated. b. the medical geneticist who analyzes the pedigree to find the mode of inheritance for the disorder. c. the parents of the first child in the family to show the trait or disorder. d. one of the grandparents or great grandparents who are in the first generation of the pedigree. e. the most common software package that geneticists use to analyze pedigrees.

a. the individual having the trait or disorder from whom the pedigree is initiated.

40. Which of the following conditions is most commonly screened for in maternal blood tests? a. Phenylketonuria and chromosome abnormalities b. Tay-Sachs disease and neural-tube defects c. Cancer and multiple sclerosis d. Chromosome abnormalities and neural tube defects e. None of the above is detected.

d. Chromosome abnormalities and neural tube defects

21. June has two brothers with Becker muscular dystrophy (BMD), a X-linked recessive condition that allows affected males to survive into adulthood. Her parents are phenotypically normal. She marries Sheldon who also has BMD. June and Sheldon have a daughter. What is the probability that this daughter will have BMD? a. Near 0 b. 1/4 c. 1/2 d. 3/4 e. 1/8

b. 1/4

25. Assuming that it is not a Y-linked trait, suggest the most likely mode of inheritance for the rare trait shown in the pedigree below. a. Autosomal recessive b. Autosomal dominant c. X-linked recessive d. X-linked dominant e. Mitochondrial

b. Autosomal dominant

18. If the characteristic followed in the pedigree is autosomal recessive, what is III-1's genotype? a. Either homozygous dominant or heterozygous b. Definitely heterozygous c. Definitely homozygous dominant d. Must be homozygous recessive e. Homozygous dominant since he is a male but a female would be heterozygous

b. Definitely heterozygous

13. The ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. What is the woman's genotype? a. Homozygous dominant b. Heterozygous c. Homozygous recessive d. Either homozygous recessive or homozygous dominant e. Cannot be determined from this information

b. Heterozygous

23. If the phenotype followed in Pedigree 3 is X-linked recessive, then what is the genotype of II-2? Assume no new mutations and complete penetrance. a. Homozygous dominant b. Heterozygous c. Homozygous recessive d. Hemizygous dominant e. Hemizygous recessive

b. Heterozygous

24. If the phenotype followed in Pedigree 3 is autosomal recessive, then what is the genotype of I-1? Assume no new mutations and complete penetrance. a. Homozygous dominant b. Heterozygous c. Homozygous recessive d. Hemizygous dominant e. Hemizygous recessive

b. Heterozygous

36. Which of the following statements is NOT correct concerning newborn screening? a. It is normally done soon after the birth of a child. b. It is particularly important to test for serious conditions where there is no treatment available. c. Most newborn testing is done by collecting a small amount of an infant's blood and then using it for analysis to detect specific genetic disorders. d. The genetic disorder phenylketonuria is one of the conditions that is usually tested for with newborn screening. e. All of the above statements are true.

b. It is particularly important to test for serious conditions where there is no treatment available.

15. Could the characteristic followed in the pedigree be caused by an autosomal dominant disease? Why or why not? a. Yes, all individuals fit the autosomal dominant inheritance pattern. b. No, the offspring of I-1 and I-2 contradict an autosomal dominant inheritance. c. No, the offspring of I-3 and I-4 contradict an autosomal dominant inheritance. d. No, the offspring of II-3 and II-4 contradict an autosomal dominant inheritance.

b. No, the offspring of I-1 and I-2 contradict an autosomal dominant inheritance.

44. Which of the following human genes shows signs of recent selection suggesting that it provides some unique human characteristic? a. DMD b. FGFR3 c. FGFR2 d. FOXP2 e. XIST

d. FOXP2

35. Heterozygous genetic screening is used mainly to a. detect genetic disorders among newborn infants. b. detect adult members of a particular population who may be heterozygous carriers for recessive disorders. c. detect in healthy adults the presence of a mutant allele that may predispose them to some serious health problem later in life. d. detect fetuses who may be heterozygous carriers for recessive disorders and may eventually be at risk of having children of their own with these disorders. e. detect adults that may be heterozygous for serious autosomal dominant disorders.

b. detect adult members of a particular population who may be heterozygous carriers for recessive disorders.

42. Preimplantation genetic testing involves a. testing a newborn infant for a genetic disorder immediately after birth. b. testing a single cell of an early embryo for a genetic disorder before the embryo is considered for implanting into the mother's uterus. c. testing multiple sperm from a man who is heterozygous for a serious genetic disorder and then using only sperm that have normal alleles for in vitro fertilizations. d. removing cells from a fetus and then testing them for a genetic disorder and then allowing abnormal fetuses to be aborted. e. testing primary oocytes (eggs) for genetic disorders before using them in in vitro fertilizations.

b. testing a single cell of an early embryo for a genetic disorder before the embryo is considered for implanting into the mother's uterus.

3. Which of the following statements is incorrect concerning an X-linked recessive trait in humans? a. An affected man often has phenotypically normal parents. b. All the sons of an affected woman will be expected to be affected. c. An affected woman almost always has an affected mother. d. An affected man usually has a mother who carries the recessive allele. e. A phenotypically normal woman whose father was affected is likely to be heterozygous for the condition.

c. An affected woman almost always has an affected mother.

31. Below are concordance rates for five different human disorders studied in monozygotic (MZ) and dizygotic (DZ) twins. _____________________________________ Concordance Disorder MZ DZ ______________________________________ A 100% 50% B 17% 16% C 56% 11% D 100% 25% E 50% 100% ________________________________________ One of the above disorders is in part caused by significant genetic effects. In addition to a significant genetic contribution toward the disorder, there are also significant environmental effects that contribute toward the disorder phenotype. Which of the above disorders would this description most likely apply to? a. A b. B c. C d. D e. E

c. C

32. In an effort to identify the influence of genetic factors on both Type 1 diabetes and Type II diabetes, researchers calculated concordance rates for monozygotic twins. Concordance rates of 30-50% have been found for Type I diabetes with concordance rates of 80% for Type II. For both kinds of diabetes, dizygotic concordance rates were about 15%. What does this information suggest concerning the relative effect of genetic and environmental factors for each type of diabetes? a. Genetic factors have little or no role in the occurrence of Type I diabetes. b. Type II diabetes is primarily determined by non-genetic factors. c. Genetic influences exert a larger role in Type II diabetes than in Type I diabetes. d. Type II diabetes appears to be caused by a single, unidentified gene. e. Environmental factors have no role in the occurrence of either type of diabetes.

c. Genetic influences exert a larger role in Type II diabetes than in Type I diabetes

34. Which of the following is not correctly identified as an advantage is using amniocentesis? a. It can be used to detect chromosome abnormalities prenatally in the fetus. b. In some cases, it can be used to obtain fetal DNA so that tests can be done to determine if the fetus may have a particular genetic disorder. c. It can normally be done as early as the sixth week of pregnancy. d. It can be used to determine if the fetus may have a neural-tube defect. e. All of the above are advantage with the use of amniocentesis.

c. It can normally be done as early as the sixth week of pregnancy.

29. Lucy is 16 weeks pregnant and undergoes maternal serum screening to measure her maternal alpha fetoprotein levels (AFP). Her AFP level is several times higher that normal levels. For which of the following disorders should Lucy be offered additional testing? a. Trisomy 21, a chromosome abnormality b. Sickle-cell disease, an autosomal recessive disorder c. Spina bifida, a neural tube defect d. Hemophila A, a sex-linked recessive disorder e. Lucy does not need additional testing for any disorder.

c. Spina bifida, a neural tube defect

28. Imagine that a human characteristic is determined by genotype only, with no environmental influence. Based on the amount of shared genetic information in MZ (monozygotic) and DZ (dizygotic) twins, what would you expect the concordance values to be in these two sets of twins? a. The concordance values would be near 100% for both types of twins. b. The concordance values would be near 50% for both types of twins. c. The concordance values should be close to 100% for MZ twins and about 50% for DZ twins. d. The concordance values should be close to 50% for MZ twins and about 25% for DZ twins. e. The concordance values should be close to 25% for MZ twins and about 75% for DZ twins.

c. The concordance values should be close to 100% for MZ twins and about 50% for DZ twins.

4. In pedigree analysis, consanguinity refers to a. mating between two heterozygous carrier parents. b. the realization that phenotypes between children and grandparents being often more closely related than between children and parents. c. mating between two closely related parents. d. a situation where the children of two parents are adopted. e. a situation where only one individual in the entire pedigree is affected with the trait or disorder.

c. mating between two closely related parents.

41. Fetal cell sorting is a(n) a. method of obtaining fetal cells through amniocentesis. b. method of obtaining fetal cells through chorionic villus sampling. c. procedure for detecting and separating fetal cells from maternal blood cells. d. invasive procedure that allows a physician to directly take blood from the fetus to analyze for genetic conditions. e. method where a fetus who has a genetic condition can be treated before birth by providing it with healthy fetal cells.

c. procedure for detecting and separating fetal cells from maternal blood cells.

22. What is/are the possible inheritance pattern(s) for the characteristic in Pedigree 2? Assume no new mutations and complete penetrance. a. Autosomal recessive only b. Autosomal dominant only c. X-linked recessive only d. X-linked dominant only e. All of the above are possible.

e. All of the above are possible.

14. The ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. The woman is expecting a child with a man who is a "nonroller." What is the probability that their first child will be a "roller"? a. 1/4 b. 0 c. 3/4 d. 1/2 e. 1

d. 1/2

26. Which of the following is not normally used to study the inheritance of human traits or disorders? a. Pedigree analysis b. Twin studies c. Adoption studies d. All of the above are used in the study of human traits or disorders. e. None of the above is used in the study of human traits or disorders.

d. All of the above are used in the study of human traits or disorders.

30. Look at the data below and explain what they say about the genetic and environmental influence on each characteristic. How did you interpret these data? (MZ = monozygotic twins and DZ = dizygotic twins.) Concordance in Trait MZ DZ Right- or left-handedness 80 75 Manic depression 80 20 a. Handedness and manic depression both have a strong genetic basis and little or no environmental basis. b. Handedness and manic depression are both strongly affected by environmental factors with little or no genetic basis. c. Handedness and manic depression are strongly affected by both environmental factors and genetic factors. d. Handedness is strongly affected by environmental factors with little or no genetic basis, while manic depression is significantly affected by genetic factors. e. Handedness is significantly affected by both environmental and genetic factors, while manic depression is significantly affected by environmental factors with little genetic basis.

d. Handedness is strongly affected by environmental factors with little or no genetic basis, while manic depression is significantly affected by genetic factors.

12. Most pedigrees showing the hypothetical human trait show the following characteristics: • Females are affected twice as frequently as males. • Affected fathers may have affected daughters but never affected sons. • Half the children of affected mothers and normal fathers are affected. What is the most likely mode of inheritance for this disorder? a. Autosomal recessive b. Autosomal dominant c. X-linked recessive d. X-linked dominant e. Y-linked

d. X-linked dominant

33. Several members of a family have a very rare form of hearing disorder. You construct the following pedigree. The most likely mode of inheritance is a. autosomal dominant since the trait does not skip generations. b. X-linked dominant since an affected woman can have both affected sons and affected daughters. c. autosomal recessive, where all the unaffected individuals are heterozygous for the condition. d. mitochondrial since affected females pass the condition on to all their children and affected males do not. e. The mode of inheritance in the above pedigree does not fit any of the previous mentioned modes in inheritance.

d. mitochondrial since affected females pass the condition on to all their children and affected males do not.

1. Two parents are phenotypically normal, but one of their four biological children has a typical autosomal recessive trait. The other three children are phenotypically normal. It is very likely that a. the affected child is a girl. b. the affected child is a boy. c. the trait was expressed by one of the grandparents of the children. d. the parents are both heterozygous for the trait. e. if the affected child eventually marries a phenotypically normal spouse, all of the their children will have the trait.

d. the parents are both heterozygous for the trait.

7. Which of the following is not a typical characteristic of human traits that follow an autosomal recessive inheritance pattern? a. They often "skip" generations. b. They appear equally in males and females. c. Parents of affected children are often phenotypically normal themselves. d. When affected individuals marry phenotypically normal individuals, their children are often phenotypically normal. e. All of the above are characteristic of autosomal recessive inheritance.

e. All of the above are characteristic of autosomal recessive inheritance.

27. If in one study with both monozygotic and dizygotic twins, the concordance value for a neurological disorder was 100% for monozygotic twins. Which of the following statements is correct? a. The concordance value for dizygotic twins will be also 100%. b. There will be no phenotypic variation in susceptibility for the disorder for all the pairs of twins in the study. c. The concordance value for dizygotic twins will be 25%. d. For dizygotic twins, all the variation in susceptibility for the disorder will be due to environmental factors. e. All the variation in susceptibility for the disorder for monozygotic twins is due to genetic factors.

e. All the variation in susceptibility for the disorder for monozygotic twins is due to genetic factors

11. Most pedigrees showing the hypothetical human trait show the following characteristics: • Only males are affected. • Affected fathers always pass the trait to sons. What is the most likely mode of inheritance for this disorder? a. Autosomal recessive b. Autosomal dominant c. X-linked recessive d. X-linked dominant e. Y-linked

e. Y-linked

43. To establish a successful and cost-effective screening program for detecting adult heterozygous carriers of an autosomal recessive disease, all of the following are important for establishing a successful program for a particular disorder except a. detection of the disorder is possible in the fetus. b. the disease is clinically significant. c. a high-risk population can be identified . d. genetic counseling is provided with the testing. e. an effective treatment is available for the disorder.

e. an effective treatment is available for the disorder.

37. Heterozygote screening normally involves a. testing healthy individuals to see if they possess mutant alleles that may make them ill later in life. b. testing newborn infants to see if they have a genetic disorder so that they can be treated immediately. c. examining fetal cells to see if they have a serious genetic disorder so thst the pregnancy can be terminated if the parents so desire. d. testing to determine if two parents are related to each other. e. testing adult members of a particular population to identify heterozygous carriers for a recessive disorder.

e. testing adult members of a particular population to identify heterozygous carriers for a recessive disorder.