BIOL . 303 EXAM II 10/30/03
( If anything seems incorrect, please bring it to my attention )
1. Nondisjunction
1. can lead to aneuploidy.
2. does not alter a karyotype.
3. turns a diploid genome into a haploid genome.
4. is responsible for familial Down syndrome.
2. In familial Down Syndrome
1. an affected individual has 46 chromosomes.
2. an affected individual displays a type of chromosomal translocation.
3. Both of the above.
4. Neither of the above.
3. A male displays the characteristics of Klinefelter syndrome (XXY). Which of his parents underwent nondisjunction during meiosis, giving rise to the gamete responsible for the syndrome?
1. his mother.
2. his father.
3. both parents.
4. there is not enough information to tell.
4. The observation that a fly heterozygous for the double Bar allele and the wild-type allele
(genotype = B
D
/B
+
) has a different phenotype than a fly that is homozygous for the Bar eye allele
(genotype = B/B) serves as an example of the phenomenon known as
1. chaos.
2. inversions.
3. incomplete penetrance.
4. position effect.

6.
5. When two genes fail to assort independently, the term normally applied is
1.
Mendelian inheritance.
2.
linkage.
3.
incomplete dominance.
4.
complementation.
Which statement is true?
1. two genes on the same chromosome can never assort independently from one another.
2. two genes on different chromosomes will assort independently from one another.
3. recombination will occur between a given pair of linked genes every time gametes are formed.
4. two genes on the same chromosome will always appear to be genetically linked to one another in a dihybrid cross.
7. When Morgan discovered genetic recombination, Morgan noticed that
1. two alleles present on the same X chromosome in a parental fruit fly are always transmitted together to the offspring.
2. two alleles present on the same X chromosome in a parental fruit fly are not always transmitted together to the offspring.
3. alleles on an X chromosome always display complete linkage.
4. alleles on the Y chromosome are linked to alleles on X.
8. Assuming that the percent recombination between A and B is 25%, the percent recombination between B and C is 37%, and the percent recombination between A and C is 50% then
1. A is not linked to B.
2. A and C are likely on the same chromosome.
3. A and B assort independently.
4. B and C are likely on different chromosomes.

9. Genetic distance within a given linkage group
1. cannot exceed 100 cM.
2. is measured in centiMorgans.
3. will vary between any two specific gene loci.
4. cannot be determined.
10. Assume that for the following genetic interval, the coefficient of coincidence = 0.50.
a b c
20.0 cM 25.0 cM
Consider the following 3-factor (trihybrid) testcross: (abc/+++) X (abc/abc). What percent of the offspring will be the products of a double crossover?
1.
45%
2.
10%
3.
5%
4.
2.5%
11. The genetic material of most living things is
1. deoxyribonucleic acid.
2. ribonucleic acid.
3. RNA.
4. polysaccharide.
12. The basic structure of a nucleotide includes the following components:
1. amino acids.
2. base, sugar, phosphate.
3. phosphorous and sulfate.
4. all of the above.

13. A difference between DNA and RNA is that
1. DNA has one less oxygen on each ribose.
2. RNA is genetic material.
3. only DNA is involved in the expression of genetic information.
4. none of the above.
14. Griffith's classic experiments with mice and Streptococcus pneumoniae
1. demonstrated that DNA is the genetic material.
2. demonstrated that the genetic material is not protein.
3. led to the discovery of the "transforming principle."
4. all of the above.
15. A DNA sample is tested for base composition. Which choice is one of the expected results?
1. A = G
2. A + T = C + G
3. A + C = T + G
4. 25% each base
16. Which of these sequences could form a hairpin?
1. 5'-GGGGTTTTCCCC-3'
2. 5'-AAAAAAAAAAAA-3'
3. 5'-ACACACACACAC-3'
4. 5'-TTTTTTCCCCCC-3'
17. If a DNA molecule is 30% cytosine (C), what is the percent guanine (G)?
1. 30%
2. 60%
3. 35%
4. 70%

Refer to the following figures for questions 18 and 19.
a b. c.
d. e.
18. Which diagram shows a nucleotide with a purine base?
1. Figure a
2. Figure b
3. Figure c
4. Figure d
19. Which figure shows one of the amino acids that was key to distinguishing DNA from protein in the Hershey and Chase experiment?
1. Figure a
2. Figure b
3. Figure d
4. Figure e
20. Which one of the following is part of the Watson-Crick model for DNA?
1. DNA is triple-stranded.
2. the DNA helix is left-handed.
3. DNA consists of two strands of deoxynucleotides with the same polarity.
4. the number of purines equals the number of pyrimidines.

21. The two strands of a DNA helix are held together (to each other) by
1. covalent bonds.
2. hydrogen bonds.
3. phosphodiester bonds.
4. glycosidic bonds.
22. If one strand of a short DNA fragment has the sequence 5'-TTTTTTTT-3' then the other strand of DNA has the sequence
1. 5'-GGGGGGGG-3'
2. 5'-CCCCCCCC-3'
3. 3'-GGGGGGGG-5'
4. 5'-AAAAAAAA-3'
23. In DNA reassociation experiments, the reassociation of complementary strands of DNA is plotted as a function of:
1. time.
2. concentration.
3. concentration and time.
4. molecular weight.
24. The simplest type of transposable elements in bacteria are known as
1. transposons.
2. insertion sequences.
3. Ds elements.
4. Ty elements.
25. Transposition can involve exchange of DNA sequences and recombination, which often leads to DNA ________.
1. acetylation
2. rearrangements
3. condensation
4. degradation

26. Almost all transposable elements
1.
encode transposase.
2.
encode antibiotic resistance.
3.
transpose via a replicative mechanism.
4.
produce flanking direct repeats upon transposition
27. With regard to eukaryotic chromatin, when one visualizes "beads-on-a-string" each bead is actually a
1. gene.
2. histone.
3. nucleosome particle.
4. 30 nanometer fiber.
28. In eukaryotic chromatin, the next highest level of organization above "beads-on-a-string" is
1. the 30 nm fiber.
2. chromatin loops.
3. the nuclear matrix.
4. the metaphase chromosome.
29. Most DNA occurring in nature is
1.
relaxed.
2.
positively supercoiled.
3.
negatively supercoiled.
4.
not complexed with proteins
30. In E. coli bacteria, which terms accurately reflect the nature of replication of the genome?
1. bidirectional and fixed point of initiation.
2. unidirectional and conservative.
3. unidirectional and fixed point of initiation.
4. multirepliconic.

31. In the Meselson-Stahl experiment, what was the density distribution of the isolated DNA molecules two generations after shifting bacteria from "heavy" to "light" growth medium?
1. 100% of the molecules were of heavy density.
2. 50% were of heavy density, 50% were intermediate density.
3. 100% were of intermediate density.
4. 50% were of light density, 50% were intermediate density.
32. The discontinuous aspect of replication of DNA is caused by
1. polymerase slippage.
2. the 5' to 3' polarity restriction.
3. trinucleotide repeats.
4. topoisomerases cutting the DNA in a random fashion.
33. The enzyme that appears to be inappropriately expressed in cancer cells and helps to maintain the very ends of eukaryotic chromosomes is called
1. topoisomerase.
2. ligase.
3. telomerase.
4. terminase.
34. The fact that there is a problem maintaining the very ends of eukaryotic chromosomes during replication has to do with
1. the fact that eukaryotic chromosomes are linear.
2. the inability of DNA polymerases to initiate synthesis without a primer.
3. the restriction that DNA synthesis must occur in a 5' to 3' direction.
4. all of the above.
35. The type of protein that unwinds a DNA helix in order for replication to proceed is called a(n):
1. unwindase.
2. single-stranded binding protein.
3. helicase.
4. none of the above.

36. Regarding prokaryotic DNA polymerases:
1. they all synthesize DNA in a 5' to 3'direction.
2. there is only one.
3. they all convert RNA to DNA.
4. they all can initiate DNA synthesis without a primer
For questions 37- 39 refer to the replication fork depicted below :
5’
3’
B A
B
B
C
5’
3’
37. Item A is called
1.
the leading strand.
2.
primase.
3.
single strand binding protein.
4.
an Okazaki fragment.
38. B is most likely:
1. an RNA primer.
2. a DNA primer.
3. DNA polymerase III.
4. an exonuclease.
39. C is most likely:
1.
DNA polymerase I
2.
RNA primase
3.
DNA polymerase

4.
helicase
3’
5’

40. The Holliday Model and Double-Strand Break Repair Model are
1.
models for homologous recombination.
2.
relevant to RNA genomes.
3.
are revealed in C o t curves.
4.
are both semiconservative replication models.