Name______

Final Exam Biol 212 General Genetics

Fall 2002 (140 points)

Please show your work for full credit. Note that there are population genetics formulas, a Chi-square table, and a genetic code table on the last two pages of the exam, for your use. The first part of the exam (#1-28) consists of multiple choice questions, to be answered on the scantron sheets provided, using a number two pencil. The last three questions on the exam (#29-31) are problems or short answer questions to be answered in the spaces provided.

Multiple Choice: Select the one best answer (4 points each)

Part I: Exam 3 questions

1. Tay-Sachs disease is inherited as an autosomal recessive disorder. In a certain large eastern European population, the frequency of Tay Sachs disease is 1 percent. If the population is assumed to be in Hardy-Weinberg equilibrium with respect to Tay-Sachs, what is the frequency of the allele that causes Tay-Sachs?

a. 0.01

b. 0.1

c. 0.9

d. 0.81

2. A partial diploid of genotype I-P+O+Z+/I+P+O+Z- will show

a. Inducible production of repressor

b. Inducible production of -galactosidase

c. Constituitive production of –galactosidase

d. No production of –galactosidase

e. Constituitive production of lactose

3. The only viable monosomy in humans is

a. XO, Turner's syndrome

b. YO, Male androgeny

c. monosomy 21

d. XYY

4. If natural selection acts to remove individuals with a trait determined by a homozygous recessive genotype (fitness=0.6), the long range tendency in the population will be toward

a. fixation of the A allele and extinction of the a allele

b. fixation of the a allele and extinction of the A allele

c. Hardy-Weinberg equilibrium

d. A balanced polymorphism

5. The mutation causing the recessive disease allele for sickle-cell anemia removes one MstII restriction site from the globin gene so that a probe, instead of hybridizing to two fragments of 1.1 kb and 0.2 kb, hybridizes to one 1.3-kb fragment. For two parents to have a 25 percent chance of a child with sickle-cell anemia

a.They must both show only fragments of 1.1 and 0.2 kb.

b.They must both show fragments of 1.3 and 0.2 kb.

c.One must show only a 1.1- and the other only a 0.2-kb fragment.

d.One must show a 1.3- and the other a 1.1- and a 0.2-kb fragment.

e.They must both show all three types of fragments.

6.A reciprocal translocation in a wild species of strawberry was discovered. The normal gene arrangement on the chromosomes was:

abcdef and mnop

The translocation gave rise to chromosomes

mndef and abcop

The reciprocal translocation heterozygote can be diagrammed as shown in the table below:

Chromosome arrangementchromosome designation (N=normal, T=translocation)

abcdefN1

mnopN2

abcopT1

mndefT2

Which chromosomes (use above designations) must separate from one another at anaphase I to form viable meiotic products?

a.N1 separates from N2, T1, and T2.

b.N1 and T1 separate from N2 and T2.

c.N2 and T1 separate from N1 and T2.

d.N1 and N2 separate from T1 and T2.

e.T1 separates from T2, N1, and N2.

7. Which of the following is not being used as a vector in gene therapy protocols?

a. adenovirus

b. adeno-associated virus (AAV)

c. bacteriophage lambda

d. retrovirus

8. The human genome

a. refers to the entire genetic make-up of human beings

b. contains a lot of repetitive DNA sequences of unknown function

c. has at least 30,000-40,000 genes, based on the draft sequence

d. all of the above are correct

9. A wild-type chromosome can be represented as ABC · DEFGH, and from this a chromosomal aberration arises that can be represented ABC · DGFEH. This is known as

a. Deletion

b.Translocation

c. Duplication

d. Paracentric inversion

10. The sequence on DNA that lac repressor binds is

a. the promoter

b. the operator

c. the permease gene

d. the I gene

11. Features of eukaryotic pre-mRNAs usually absent in prokaryotic mRNAs include

a. their introns must be removed by splicing

b. a 5' cap and 3' poly (A) tail are added

c. they are usually polycistronic

d. both a and b are correct

e. all of the above

12. In a human population, the genotype frequencies at one locus are 0.5 AA, 0.4 Aa and 0.1 aa. The frequency of the A allele is

a. 0.20

b. 0.32

c. 0.50

d. 0.70

13. VNTRs can be used in DNA fingerprinting because

a. all individuals have the same number of tandem repeats

b. most individuals will have different numbers of tandem repeats

c. the expression of every gene is tested on a single slide

d. known genes that cause genetic diseases are tested

14. Alleles for the genetic disorder, sickle cell anemia provide a selective advantage in equatorial climates where malaria frequently occurs. This is an example of

a. mutation

b. heterozygote superiority

c. genetic drift

d. directional selection

Part II: Cumulative questions

15. Two genes are separated by 20 map units on the chromosome. Assuming no interference, from this one can infer that

a. the recombination frequency for the two genes is 2%.

b. the recombination frequency for the two genes is 10%.

c. the recombination frequency for the two genes is 20%.

d. The genes are assorting independently.

16. The following pedigree shows a human hereditary trait

Is the trait most likely inherited as an

a. autosomal dominant

b. autosomal recessive

c. X-linked dominant

d. X-linked recessive

17. The chromosomal make-up of an individual is its

a. karyotype

b. gamete

c. polyploidy

d. tetrad

18. Which of the following is not an assumption of the Hardy-Weinberg equilibrium?

a. No new mutation.

b. No natural selection.

c. No immigration

d. Non-random mating.

19. The term phenotype describes the

a. specific combination of alleles in a cell

b. fundamental unit of heredity

c. physical location of a gene on a chromosome

d. outward appearance of some characteristic in an individual

20. A protein fragment has the following sequence NH2-Pro-Met-Phe-Tyr-Cys-COOH.

An mRNA that could be translated to give this protein (5’ ---> 3’) would be:

a. GCAAUAGAACAUGGG

b. CCCAUGUUCUAUUGC

c. CCCATGTTCTATTGC

d. CGTTATCTTGTACCC

e. GCAATAGAACATGGG

21. A sequence of DNA that is labeled with 32P and used to detect a particular gene of interest in a Southern Blot is called ______.

a. DNA clone

b. DNA library

c. DNA probe

d. gene map

22. A corn plant known to be hybrid for three linked genes is testcrossed. The progeny phenotypes and frequencies are

a+c 20

+b+ 10

++c 368

ab+ 375

a++ 45

+bc 50

+++ 2

abc 4

The order of the three genes on the chromosome is

a. a—b—c

b. b—a—c

c. a—c—b

d. c—b—a

23. In order to grow, an E. coli leu- mutant (unable to synthesize the amino acid leucine) must be provided with

a. minimal medium

b. minimal medium containing streptomycin

c. minimal medium containing proline

d. minimal medium containing leucine

24. In a mating of an Hfr strain that is a+b+c+strs to an F- strain that is a-b-c-strr, the prototrophic markers were transferred as follows: a+ after 5 min, b+ after 15 min and c+ after 2 min. Therefore the order of the genes and the F factor (F) on the chromosome in the Hfr strain was:

a. F--a--b--c

b. F--c--b--a

c. F--b--a--c

d. F--c--a--b

25. If genes for two traits showing simple dominance are unlinked and assorting independently, a cross between two individuals which are heterozygous for both traits should result in

a. a 9:3:4 ratio of phenotypes

b. a 9:3:3:1 ratio of phenotypes

c. a 3:1 ratio of phenotypes

d. a 9:3:3:1 ratio of genotypes

26. The probability that two individuals who are heterozygous for an autosomal recessive trait will produce three out of three affected children is

a. 1/4

b. 3/4

c. 1/16

d. 1/64

27. If two individuals AB/ab and ab/ab are crossed and produce an F1 generation, which of the following genotypes in the offspring would be considered recombinants?

a. AB/ab

b. ab/ab

c. Ab/ab

d. none of the above

28. (Bonus question) The plasmid vector pUC18 has a gene for ampicillin resistance (AmpR) and the gene encoding β-galactosidase (lac Z+). The Lac Z gene is cut with a restriction enzyme and donor DNA treated with the same enzyme is added. After ligation of the foreign DNA into the lac Z gene, what genotype needs to be selected to identify recombinants?

a. AmpRlacZ+

b. AmpRlacZ-

c. AmpSlacZ+

d. AmpSlacZ-

Problems and short answer: Show your work for full credit

29. (10 points) Select one of the following genetic diseases (or any other disease you are familiar with that is due to a single gene defect). Outline what you know about the disease. For full credit, discuss most or all of the following points in your answer.

  1. Describe the symptoms of the disease.
  2. How is the disease inherited? Is it recessive or dominant, X-linked or autosomal?
  3. Identify the gene that is altered in the disease.
  4. Explain how knowledge of mutations in the protein coding region help account for aspects of the disease.
  5. Identify possible ways of diagnosing or treating the disease.

Phenylketonuria

Sickle cell anemia

Cystic fibrosis

Muscular dystrophy

Huntington's disease

30. (12 pts.) Resistance to HIV virus infection is determined by the chemokine receptor gene, CCR5. The receptor enables HIV virus to cross the plasma membrane of particular T lymphocytes, a necessary step for an HIV infection to progress. The resistance mutation is determined by a deletion of 32 bp (32) with the coding region for the receptor.

a. Suggest why the 32 deletion in the receptor gene results in a resistance phenotype when present in homozygous recessive individuals.

(b) The normal (dominant) CCR5 allele will be symbolized by A, and the recessive 32 mutant allele will be designated a. The CCR532 is much more common in Caucasian populations than among other groups. In a population of 715 Chinese individuals tested for CCR5 alleles, the following genotypes were found:

AA699Aa16aa0

Test (using the Chi-squared test) whether the genotypic frequencies conform to a Hardy-Weinberg distribution. Note that there is only one degree of freedom because the three genotypic classes are completely specified by two allelic frequencies.

genotypeobsexpobs-expd2d2/exp

AA______

Aa______

aa______

Degrees of freedom = 1X2 = ______

X2 critical value at 0.05 probability = ______

(d) Would you accept or reject your hypothesis that the population is in Hardy-Weinberg equilibrium with respect to the CCR5 alleles?

31. (10 points) Diagram the first phase of meiosis (meiosis I) in the following meiotic precursor cell. Clearly indicate important stages and events (2n = 4 chromosomes)

Hardy Weinberg Equilibrium is defined by

p2 + 2pq + q2

Where p2 = AA

2pq = Aa or heterozygote

q2 = aa or recessive trait

Genetic code

Chi-square table

1