Sample questions for Exam II. The questions below are from previous exams. Your actual test
will consist of 40 multiple choice questions. Beware—use these questions as a “guide” to the
types of questions you may expect, but realize that course content does change from year to year.
Please review your lecture notes and also try the questions at the end of each chapter of your
book.
1. 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 likely display linkage.
3. two genes on the same chromosome will always appear to be genetically linked to one
another in a dihybrid cross.
4. if two genes are genetically linked, the frequency of recombination between them will
be less than 50%.
2. Assuming that genes "A" and "B" display complete linkage (that is, no recombination between
them), how many different phenotypes should appear among the offspring of the cross AaBb X
aabb ?
1. 2
2. 1
3. 4
4. can't tell
3. Genes on the same chromosome that are more than 50 map units apart
1. produce only crossover gametes.
2. must reside on opposite sides of the centromere.
3. are too far apart to produce crossover gametes.
4. behave no differently than if they were on different chromosomes.
4.
The amount of recombination between two loci
1. increases when each locus is heterozygous.
2. can be estimated by self-fertilizing an organism and observing the offspring.
3. is a function of the physical distance between the loci.
4. is greater in somatic cells than germ cells.
5. Mapping experiments become less accurate when the distances between genes become large
because
1. crossover gametes become less common.
2. multiple crossovers are more common.
3. interference is greater when the distance between genes is large.
4. recombination occurs less frequently in long chromosomes.
6. The frequency of crossover between genes A and B is 7.5%, and between B and C
is 34.5%, and between A and C is 41.4%. What is the order of these three genes?
1. B C A
2. A B C
3. C A B
4. It cannot be determined from these data.
7. If a mouse with the genotype AaBb is test-crossed, what proportion of offspring genotypes
would Mendel have expected?
1. 25% of each possible combination of traits: A and B, A and b, a and B, and a
and b.
2. 9/16 would show A and B, 3/16 would show A and b, 3/16 would show a and B,
and 1/16 would show a and b.
3. Half of the offspring showing both the A and B phenotypes and half showing both
the a and b phenotypes.
4. 3/4 would show A and B, while 1/4 would show a and b.
8. In the example above, what offspring would be expected if the two genes are 10 map units
apart and the heterozygote has the dominant alleles on one chromosome and the recessive alleles
on the other?
1. 45% of the offspring will exhibit A and B, 45% will exhibit a and b, 5% will exhibit A
and b, and 5% will exhibit a and B.
2. 40% of the offspring will exhibit A and B, 40% will exhibit a and b, 10% will exhibit
A and b, and 10% will exhibit a and B.
3. 45% of the offspring will exhibit A and b, 45% will exhibit a and B, 5% will exhibit A
and B, and 5% will exhibit a and b.
4. 25% of each possible combination of traits: A and B, A and b, a and B, and a and b
9. 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.
10.
The genetic material of most living things has each of the following properties EXCEPT:
1. it encodes much information.
2. it never changes.
3. it has the ability to be replicated.
4. it has the capability of being mutated.
11.
In Hershey and Chase's classic experiments with radioactively labeled phages
1. the sulfur contained in DNA was radiolabeled.
2. protein was demonstrated to be the genetic material.
3. the phosphorous of proteins was radiolabeled.
4. infection rather than transfection was used.
12.
Avery, McLeod and McCarty had which of the following results?
1. DNase destroyed the transforming activity.
2. The transforming principle was too complex and difficult to be purified.
3. RNase destroyed the transforming activity.
4. Protease destroyed the transforming activity
13.
HIV, the AIDS virus, like other retroviruses
1. has a genome made of DNA.
2. uses reverse transcriptase to convert RNA to DNA.
3. neither a nor b.
4. both a and b.
14.
A difference between DNA and RNA is that
1. RNA is genetic material.
2. only DNA is involved in the expression of genetic information.
3. DNA has one extra oxygen on each ribose.
4. none of the above.
15.
Which of the following is a purine?
1. adenine.
2. cytosine.
3. thymine.
4. adenoid.
16.
According to "Chargaff's rules" regarding base-pairing,
1. purines = pyrimidines
2. there may be more "A" than "G" in DNA
3. the percent "G + C" varies from organism to organism.
4. all of the above.
17.
If a sample of DNA has a base composition of 20 percent guanine, which of the
following statements is true?
1. the AT to GC ratio must be equal to 1.
2. the ratio of purines to pyrimidines must be greater than 1.
3. the amount of the other purine adenine must also equal 20 percent.
4. the amount of thymine must equal 30 percent.
18.
Each of the following is part of the original Watson-Crick model for DNA EXCEPT
1. DNA consists of antiparallel strands of nucleotides.
2. the DNA helix is right-handed.
3. DNA can be triple-stranded.
4. DNA strands are complementary to one another.
19.
Which of the following is a pyrimidine?
1. adenine.
2. cytosine.
3. guanine.
4. tyrosine.
20.
If one strand of a short DNA fragment has the sequence
5'-GCGCGCGCGC-3' then the other strand of DNA has the sequence
1. 5'-ATATATATAT-3'
2. 5'-GCGCGCGCGC-3'
3. 5'-TATATATATA-3'
4. 5'-CGCGCGCGCG-3'
21. In DNA, a nitrogenous base is attached to the deoxyribose by
1. a phosphodiester bond.
2. hydrogen bonds.
3. an ionic bond.
4. none of the above.
22.
Reassociation kinetics experiments reveal that
1. DNA is very easy to melt.
2. DNA cannot be reannealed once melted.
3. the kinetics of reassociation says nothing about genomic structure.
4. eukaryotic genomes contain many repeated sequences.
23.
Bacterial strain "A" has a genome with a Cot0.5 value of "Y" while bacterial strain "B"
has a genome with a Cot0.5 value of "3Y". If the size of the genome for strain A is "X" base pairs,
then the size of the genome of strain "B" is best approximated by:
1. 3X base pairs.
2. 2X base pairs.
3. X/2 base pairs.
4. X3 base pairs.
24.
In the Meselson-Stahl experiment in which replication in bacteria was shown to be
semiconservative, 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. 100% were of intermediate density
3. 50% were of heavy density, 50% were intermediate density
4. 50% were of light density, 50% were intermediate density.
25. 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.
26.
Which of the following is required for replication of DNA in bacteria?
1. RNA primase.
2. reverse transcriptase.
3. telomerase
4. all of the above.
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.
What is the general term given to enzymes that control supercoiling?
1. topoisomerases
2. unwindases
3. nucleases
4. helicases
29.
Which of the following statements is true of the topology of DNA found in nature?
1. DNA is typically underwound and positively supercoiled.
2. DNA is typically underwound and negatively supercoiled.
3. DNA in nature is relaxed (no supercoiling).
4. DNA is typically overwound and positively supercoiled.
30.
Analysis of the human genome has revealed that about half (or maybe more) of the
human genome seems to be composed of
1. protein-coding genes.
2. ribosomal RNA genes.
3. transposable elements (active or inactive).
4. satellite sequences.
31.
If a person has trisomy for chromosome 13, a somatic cell from this individual has a total
of how many chromosomes?
1. 23
2. 24
3. 69
4. 47
32. Chromosomal inversions can bring about phenotypic changes. This is best explained by the
phenomenon known as:
1. polyploidy.
2. genetic deletion.
3. position effect.
4. aneuploidy.
33.
Familial Down syndrome is caused by:
1. a centric fusion.
2. position effect.
3. nondisjunction.
4. genomic imprinting.
34.
The simplest of all transposable elements is called a(n)
1. Ac element.
2. P element.
3. insertion sequence.
4. transposon.
35.
The so-called "C-value paradox" says that
1. eukaryotes seem to have too little DNA.
2. prokaryotes seem to have too much DNA.
3. prokaryotes seem to have too little DNA.
4. there is a lot of DNA in eukaryotes that has no known function.