Biology 303 EXAM II 10/21/04 NAME________________________________
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This exam consists of 40 multiple choice questions worth 2.5 points each. On the separate testing form , please fill-in the single best choice for each question. Be sure to fill-out your student number and name on the answer sheet. Good luck!
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1. When two genes fail to assort independently, the term normally applied is
1.
Mendelian inheritance.
2.
linkage.
3.
incomplete dominance.
4.
complementation.
2. 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.
3. 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.
4. If 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.

6.
5. A female fruit fly heterozygous for three linked mutant alleles a,b,c, (genotype AaBbCc) is crossed with a male fly that is homozygous recessive for all three mutant alleles. If the phenotypes of the most common offspring are ABc and abC, and the least common offspring are
ABC and abc, then the order of the genes a b c on the chromosome is:
1. a b c
2. b a c
3. b c a
4. not enough information to tell.
Assume that for the following genetic interval there is no interference.
a b
20.0 cM 25.0 cM
c
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%
7. For the above question, if the coefficient of coincidence is 0.5, then what percent of the offspring will be the products of a double crossover?
1. 45%
2. 10%
3. 5%
4. 2.5%

8. Consider the following table of data from a synteny test using mouse/human hybrid cells for assigning genes to human chromosomes.
------------------------------------------------------------------------------------ hybrid human chromosomes human gene product cell: present: present:
I 1 2 3 4 5 6 A B
II 1 3 4 7 8 9 A B C
III 1 2 7 8 A
------------------------------------------------------------------------------------
Based on the above data, the gene that produces product C is located on human chromosome number:
1. 1
2. 2
3. 9
4. can't tell.
9. Genes A, B, C, and D are on the same chromosome. Here is some data for the frequency of crossing over between these four genes:
Gene pair: Percent recombination between the pair:
A,B
B,C
C,D
A,C
10
45
5
35
A,D 30
What is the order of the four genes on the chromosome?
1. B A C D
2. B A D C
3. A B C D
4. there's insufficient data to make this determination.

10. In bacterial conjugation
1. genetic material is transferred in a unidirectional fashion.
2. an F-factor is transferred from an F
-
strain to an F
+ strain.
3. bacteria do not have to physically contact each other for genetic exchange to occur.
4. DNA is transferred through a phage.
11. In the formation of an Hfr strain of bacteria
1. an F element integrates into the chromosome of a bacterial cell.
2. an F element pops out of the chromosome of a bacterial cell.
3. an F' element is transferred between bacteria.
4. the Hfr strain that forms is a merozygote.
12. One bacterial Hfr strain transfers genes in the order A--B--C--D--> while a second Hfr strain transfers genes in the order B--C--D--A-->. The most likely explanation for this is that
1. one strain actually carries an F' element and is a merozygote.
2. the F factor integrated at the same site but in opposite orientations in the two strains.
3. the F factor integrated at different sites and in opposite orientations in the two strains.
4. the F factor integrated at different sites but in the same orientation in the two strains.
13. The genetic material of most living things is
1. deoxyribonucleic acid.
2. ribonucleic acid.
3. RNA.
4. polysaccharide.
14. 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.

15. 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.
16. Griffith's classic experiments with mice and Diplococcus 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.
17. Which of the following clusters of terms accurately describes DNA as it is generally viewed to exist in prokaryotes and eukaryotes?
1. Double-stranded, parallel, (A+T)/(C+G)= variable, (A+G)/(C+T)=1.0
2. Single-stranded, antiparallel, (A+T)/(C+G)=1.0, (A+G)/C+T)=1.0
3. Double-stranded, antiparallel, (A+T)/(C+G)=variable, (A+G)/(C+T)=1.0
4. Double-stranded, antiparallel, (A+T)/C+G)=1.0, (A+G)/(C+T)=variable
18. The AIDS virus, like other retroviruses ,
1. has a genome made of DNA.
2. uses reverse transcriptase to convert RNA to DNA.
3. infects only bacteria.
4. is a free-living organism.
19. Which of the following is a purine?
1. adenine.
2. cytosine.
3. thymine.
4. none of the above.

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. In DNA, each nitrogenous base is directly covalently attached to
1. a phosphate group.
2. a deoxyribose.
3. a ribose.
4. none of the above.
22. 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.
23. 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'
24. In DNA reassociation experiments, the reassociation of complementary strands of DNA is plotted as a function of:
1. time.
2. concentration.
3. concentration multiplied by time.
4. molecular weight.

25. The value of Cot
0.5
for the genomic DNA of a prokaryote is directly related to the
1. number of chromosomes.
2. amount of repetitive DNA in the genome.
3. size of the genome.
4. size of the nucleus.
26. 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.
27. 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.
28. 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.
29. 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.

30. 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.
31. During replication of DNA, strand elongation proceeds
1. in a 5' to 3' direction on the leading strand, but in a 3' to 5' direction on the
lagging strand.
2. in a 3' to 5' direction on the leading strand, but in a 5' to 3' direction on the
lagging strand.
3. in a 5' to 3' direction on both the leading and lagging strands.
4. in a 3' to 5' direction on both the leading and lagging strands.
32. In Luria and Delbruck's classic experiments to distinguish between "spontaneous" versus
"adaptive" mutation,
1. evidence for spontaneous mutation was produced.
2. evidence for adaptive mutation was produced.
3. evidence that DNA is the genetic material was produced.
4. all of the above.
33. A class of mutations which results in multiple contiguous amino acid changes in proteins is likely to be the following:
1. frameshift.
2. base analogue.
3. transversion.
4. transition.

34. Which statement is true?
1. DNA damage and mutation are the same thing.
2. DNA damage is defined as permanent change in the nucleotide sequence.
3. although DNA damage doesn't necessarily lead to mutation, when a mutation does
occur it is always caused by DNA damage.
4. DNA damage can lead to mutation, but doesn't always.
35. An organism that is deficient in the biosynthesis of a particular important nutrient is called a(n)
1. prototroph.
2. auxotroph.
3. nutritroph.
4. dead organism.
36. A tautomeric shift
1. is typically induced by high-energy radiation.
2. occurs only in prokaryotes.
3. can lead to a transversion mutation.
4. can produce a transition mutation.
37. The "abnormal" tautomeric form of guanine hydrogen bonds well with
1. the abnormal form of adenine.
2. the normal form of guanine.
3. the normal form of cytosine.
4. the normal form of thymine.
38. In mammals, DNA double-strand breaks may be repaired by
1. mismatch repair.
2. base excision repair.
3. nucleotide excision repair.
4. nonhomologous end-joining

39. Thymine dimers may be repaired by
1. photoreactivation and excision repair in humans.
2. excision repair but not by photoreactivation in humans
3. oxidative damage.
4. telomerase.
40. The simplest type of transposable elements in bacteria are known as
1. transposons.
2. insertion sequences.
3. Ds elements.
4. Ty elements.

ANSWER KEY
Question # CORRECT ANSWER
1 2
2 2
3 2
4 2
5 3
6 3
7 4
8 3
9 2
10 1
11 1
12 4
13 1
14 2
15 1
16 3
17 3
18 2
19 1
20 4
21 2
22 2
23 4
24 3
25 3
26 1
27 4
28 2
29 3
30 4
31 3
32 1
33 1
34 4
35 2
36 4
37 4
38 4
39 2
40 2