Bio 97 2000 Final Exam

Choose the most correct answer. If none of the answers seems exactly right to you, pick the closest (unless one of the choices is something like "none of the above").

Notes for all questions:

Affected = has the disease

Unaffected = does not have the disease (but may be a carrier if the disease is recessive)

Normal = does not have the disease and is not a carrier.

For all questions, assume any trait or disease mentioned has 100% penetrance.

All diseases mentioned are genetic diseases (except, perhaps, for Snoopy's disease - see question 12)

1. (20%) On average, the DNA sequence of any two human beings is 99.9% identical. However, with respect to those polymorphic alleles that make us all different from one another, any two gametes produced by a given individual...

1. Are genetically identical to each other
2. Are genetically identical to a somatic cell of the individual who produced them
3. Are 1/2 (50%) identical to each other
4. Are not at all genetically identical to each other; that's why we're all different
5. A and B

2. (66%) The complement of the DNA sequence 5'-AGC-3' is?

1. 5'-AGC-3'
2. 5'-CGA-3'
3. 5'-CTG-3'
4. 5'-TCG'-3'
5. 5'-GCT-3'

3. (87%) The following statements refer to Duchenne Muscular Dystrophy (DMD), a single-gene, x-linked recessive disorder. Which of the following statements (A-D) is FALSE (pick E if you think A-D are all true).

1. If a female carrier of DMD mates with a normal man, half of her sons will be affected, on average
2. If a female carrier of DMD mates with a normal man, half of her daughters will be carriers, on average
3. If a female carrier of DMD mates with a male affected with DMD, all of their sons will be affected
4. If a male affected with DMD mates with a normal woman, all of his daughters will be carriers
5. None of the statements are false

4. (71%) Which of the following statements (A-D) is FALSE (pick E if you think A-D are all true):

1. Human somatic cells have 46 chromosomes
2. In humans, polyploidy is lethal before or shortly after birth
3. Non-disjunction is the most common cause of aneuploidy
4. In human females, one copy of the X chromosome is randomly inactivated in all somatic cells
5. None of the statements are false

5. (86%) There is 15% percent recombination between genes A and B. There is 11% percent recombination between genes A and D. There is 24% percent recombination between genes B and D. The order of these genes is most likely:

1. A-B-D
2. A-D-B
3. D-B-A
4. B-A-D
5. The three genes are clearly on different chromosomes

6. (72%) Which of the following statements about chromosomal rearrangements is NOT true:

1. Chromosomal rearrangements cannot be passed from generation to generation to generation
2. Conceptions with a gross chromosomal rearrangement usually abort spontaneously
3. Balanced chromosomal rearrangements typically do not cause severe symptoms in carriers
4. Duplications and deletions can result from unequal crossing over
5. A minimum of 10-15% of conceptions have a chromosomal abnormality

7. (87%) Which of the following gross chromosomal rearrangements would be expected to have the most severe phenotypic consequences:

1. reciprocal translocation
2. Robertsonian translocation
3. inversion
4. deletion
5. duplication

8. (65%) Which of the following is NOT true of alleles created by nonsense substitutions or frameshift:

1. They are often recessive to the wild-type allele
2. They can be dominant, such as in the case of haploinsufficiency
3. They usually encode a non-functional polypeptide
4. They are less likely to encode a non-functional polypeptide than alleles created by missense substitutions
5. They are often the cancer-causing alleles of tumor-suppressor genes

9. (57%) Which of the following statements is FALSE:

1. Cancer is a genetic disease of somatic cells
2. Somatic mutations are involved in many major diseases in the U.S., including cancer, heart disease, diabetes and schizophrenia
3. All the cells in a cancerous tumor have originated from a single progenitor cell
4. Mutations in several distinct genes are required for a normal cell to become cancerous
5. A predisposition to some types of cancer can also be inherited

10. (75%) Fill in the blanks. A gene that encodes a protein required for the repair of certain types of DNA damage is likely to be a _______. A gene that encodes a protein required to relay a signal telling a non-dividing cell to divide is likely to be a _______.

1. oncogene; tumor-suppressor gene
2. tumor-suppressor gene; oncogene
3. oncogene; oncogene
4. tumor-suppressor gene; tumor-suppressor gene
5. malignant, hemizygous

11. (93%) Which of the following would NOT be expected to cause allele frequencies to vary over time

1. Migration
2. Mutation
3. Random mating
4. Genetic Drift
5. Natural selection

12. (14%) A man and a woman, both affected with Snoopy's disease, mate and have four unaffected children. Which of the following is the LEAST likely explanation for this pattern of inheritance.

1. Non-genetic etiology (cause) of the disease, such as a viral or bacterial infection
2. A disease characterized by locus heterogeneity (that is, a multigenic disease)
3. Multifactorial inheritance of the disease
4. Meiotic recombination, resulting in the unlinking of disease-causing alleles
5. Autosomal dominant inheritance of the disease

13. (92%) You are denied a job in the emergency room because you are homozygous for an allele of the serotonin receptor that is associated with a higher level of anxiety. The policy of the HMO that runs the emergency room is that anxious doctors make bad (i.e., unprofitable) doctors. You decide to sue. Which of the following is the your best argument to use at the trial:

1. Anxiety is a multifactorial trait and you may well be favorably disposed for the many other environmental and genetic factors that contribute to the variance in anxiety
2. Anxiety is a genetic disease of somatic cells
3. Assuming Hardy-Weinberg equilibrium, you should be no more or less anxious than anybody else in the population
4. Okay, so you hated all your science courses in college. You still think medicine is the right career for you
5. Clearly, an autosomal dominant mode of inheritance can be ruled out for anxiety

14. (29%) Which of the following DNA sequences is the most likely to be a 6-basepair recognition site for a restriction enzyme used in gene cloning? (NOTE: only the top strand is shown)

1. 5'-AAAAAA-3'
2. 5'-AACGTT-3'
3. 5'-AGAATC-3'
4. 5'-GATTAG'-3'
5. 5'-GAAATC-3'

15. (58%) You want to clone a human gene. Which of the following will you NOT need:

1. Human DNA
2. A plasmid vector
3. A restriction enzyme
4. DNA ligase
5. an enucleated embryonic cell

16 & 17. (44%) Which of the following is NOT true about non-disjunction of the sex chromosomes during meiosis I in a human male?

1. It results in 4 aneuploid gametes
2. It can result in Turner syndrome (45, X)
3. It can result in Klinefelter syndrome (47, XXY)
4. It can result in double -Y syndrome (47, XYY)
5. The risk of it occurring does not dramatically increase with age

18 & 19. (82%) The cross ab/ab x AB/ab is performed. If the two genes in question are completely linked, the progeny will have the genotypes AaBb :Aabb : aaBb : aabb in the ratio...

1. 1 : 1 : 1 : 1
2. 1 : 0 : 0 : 1
3. 0 : 1 : 1 : 0
4. 1 : 0 : 1 : 0
5. 9 : 3 : 3 : 1

20 & 21. (88%) The test cross ab/ab x AB/ab is performed. The following number of progeny of each genotype are obtained: 390 AaBb, 110 Aabb, 90 aaBb, 410 aabb. What is the distance (in map units) between the two genes in question?

1. 50 centiMorgans (cM)
2. 25 cM
3. 20 cM
4. 10 cM
5. The genes are not linked

22 & 23. (22%) The genes for HPRT (mutation of which causes Lesch-Nyhan syndrome) and Factor VIII (mutation of which causes hemophilia A) are located about 15 cM apart on the X chromosome. A male afflicted with both Lesch-Nyhan syndrome and hemophilia A has an unaffected daughter. She mates with a normal man and has a son who has hemophilia A . Approximately what are the chances that he (the son) is also afflicted with Lesch-Nyhan syndrome?

1. 100%
2. 85%
3. 50%
4. 25%
5. 15%

24 & 25. (88%) A woman claims that either basketball stars Shaq ONeil or Dennis Rodman is the father of her child. DNA samples are taken from her (M), her child (C), Shaq (S) and Rodman (R), and typed for a polymorphism. The figure shows the banding pattern obtained by the Southern blot procedure.

1. Shaq may be the father, but Rodman cannot be
2. Shaq cannot be the father, but Rodman may be
3. Shaq cannot the father, and Rodman cannot be the father either
4. Either man could be the father
5. Shaq is the father and Rodman is the mother

26 & 27. (91%) The members of this family have been DNA typed for a 3-allele polymorphic marker. The genotype of each person with respect to the marker is shown below the pedigree symbols. Three people (filled-in symbols) are affected with an autosomal dominant disease. If the marker is closely linked to the disease gene, then the disease-causing allele in Dad is on the same single chromosome as

1. Allele #1 of the marker
2. Allele #2 of the marker
3. Allele #3 of the marker
4. The pedigree does not support the assumption of linkage of the marker to the disease gene
5. None of the above, as Dad must be homozygous for the disease gene

28 & 29. (36%) A deamination occurs on the cytosine residue in the following DNA sequence 5'-AGAATTCG-3'. After two cell divisions (hence two rounds of DNA replication) the damage has been fixed as a mutation. The sequence of the same stretch of DNA is now:

1. 5'-AGAATTCG-3'
2. 5'-AGAATTUG-3'
3. 5'-AGAATTTG-3'
4. 5'-AGAATTG-3'
5. 5'-AGAATTAG-3'

30 & 31. (44%) For the population of an isolated south seas island, all the conditions of Hardy-Weinberg equilibrium are met except that inbreeding is rampant. Then the entire population is converted to a new religion that prohibits inbreeding, and the islanders begin to practice random mating. As a result of this change it can be predicted that...

1. Allele frequencies will change but genotype frequencies will not
2. Genotype frequencies will change but allele frequencies will not
3. Neither allele frequencies nor genotype frequencies will change
4. Both allele frequencies and genotype frequencies will change
5. The incidence of rare recessive diseases will increase

32 & 33. (38%) Your uncle (your mother's brother) has a rare genetic disease that is inherited in an autosomal recessive manner, but you, your parents and all your grandparents are unaffected. What is the approximate chance that you are a carrier (heterozygote) for this disease?

1. 1/6, or 17%
2. 1/4, or 25%
3. 1/3, or 33%
4. 1/2, or 50%
5. 2/3, or 67%

34 & 35. (74%) The fraction of your alleles that you share with your uncle is...

1. 1/16
2. 1/8
3. 1/4
4. 1/3
5. 1/2

36 & 37. (86%) Marfan syndrome is an autosomal recessive disease with an incidence of 1/10,000. What is the approximate frequency of heterozygote carriers for this disease? Assume Hardy-Weinberg conditions apply.

1. 1/50, or 2%
2. 1/100, or 1%
3. 1/1000, or 0.1%
4. 1/10, or 10%
5. 1/4, or 25%

38 & 39. (67%) The ABO blood group is transmitted in humans as follows: The A and B alleles are dominant to the O allele but codominant with each other. The O phenotype (OO genotype) is known as the "universal donor" in small-volume blood transfusions, whereas the AB phenotype (AB genotype) can be considered a "universal recipient". A certain human population is at Hardy-Weinberg equilibrium with respect to blood type, with allele frequencies A = 0.5, B = 0.2, O = 0.3. In this population(fill in the blanks), universal donors occur at a frequency of _______, whereas universal recipients occur at a frequency of _______.

1. 0.25; 0.30
2. 0.09; 0.20
3. 0.3; 0.7
4. 0.06; 0.04
5. 0.15; 0.10

40 & 41. (80%) Blood pressure is a multifactorial trait with a heritability of 0.6. A study is conducted on identical (monozygotic, or MZ) twins that were separated at birth and reared apart. They are compared to fraternal (dizygotic, or DZ) twins reared apart (NOTE: This often happens with twins given up for adoption). The most likely outcome of this study is that...

1. MZ twins will have almost identical blood pressures, much more so than DZ twins
2. MZ twins will have more similar blood pressures than DZ twins, but there will still be significant variation between MZ twins due to environmental factors
3. Both MZ and DZ twins will have very similar blood pressures
4. DZ twins will have more similar blood pressures than MZ twins
5. Environmental factors more important than genetic factors with regard to blood pressure

42 & 43. (90%) A girl is born with Yutski's disease, but her parents are unaffected. Which type(s) of inheritance can be ruled out for Yutski's disease:

1. Autsomal recessive
2. Autosomal dominant
3. X-linked recessive
4. X-linked dominant
5. B, C and D

44 & 45. (45%) Which of the following statements is the most true about rare recessive alleles:

1. Disadvantageous ones could be rapidly eliminated from the gene pool if modern medicine did not prolong the life of people affected by recessive genetic diseases
2. People who carry disadvantageous ones should probably not have children
3. First cousins are far more likely to share one than two unrelated people
4. On average, a new one is created every time a gamete is formed
5. C and D are both true