Name_________________________________________
November 9, 2004
BIO184 Genetics
Exam 2
This examination is worth 100 points. There are questions on pages. Read through the
questions completely before answering the questions. If you are unclear about a
question, please ask me.
Good luck
Part A: Multiple Choice: Answer with the best choice. Make sure that you clearly circle the
correct answer and erase any erroneous marks. (4 pts each)
1.
AG
= 1
CT
for double-stranded helical DNA.
a) True
b) False
Answer: A
2.The DNA of a eukaryotic chromosome is one long double helix.
a) True
b) False
Answer: A
3. If DNA polymerase could catalyze sugar phosphate bonds in both directions equally well what
would no longer be seen during synthesis?
a) replication bubble
*b) Okazaki fragments
c) RNA primer
d) telomerase
e) both a and b
4.If phages are labeled with radioactive sulfur and allowed to infect bacterial cells, the phage progeny
resulting from lysis are expected
* a) to be non-radioactive.
b) to have radioactive DNA.
c) to have radioactive proteins.
d) to have radioactive DNA and proteins.
e) to have radioactive carbohydrates.
5) Which of the following is not true of DNA?
a) It is acidic
b) It contains deoxyribose
c) It is found in cell nuclei
d) It contains phosphate
e) it contains proteins
6)
a)
b)
c)
d)
e)
The group of enzymes able to relax supercoils in DNA is called:
primases
helicases
topoisomerases
telomeres
ligases
7) Ocassionally, a loss of function mutation may occur in the telomerase enzyme in a cell.
What is likely to be the result of this mutation on the DNA in the cell over the course of
several rounds of mitosis?
a) Chromosome length will gradually increase
b) Chromosome length will gradually decrease
c) Chromosome length will stay constant
d) Chromosomes will fail to dissociate after replication
e) None of the above
8) In general, which of the following usually has a greater chance of lethality than the
others?
a) inversions
b) duplications
c) deletions
d) translocations
e) none of the above
9) Inversions may be hard to detect because they:
a) never visibly change chromosome banding patterns
b) increase recombination in heterozygotes
c) do not usually cause an abnormal phenotype
d) normally are removed immediately in natural populations
10) Down syndrome can result from:
a) three copies of chromosome 21
b) a translocation of a part of chromosome 21
c) a reciprocal translocation between any two autosomes
d) a and b
e) a, b and c
11) Which of the following is not an aneuploidy?
a) monosomy
b) tetraploid
c) trisomy
d) tetrasomy
12) Hybrids in which the chromosome sets come from two distinct, though related, species
are known as:
a) autopolyploids
b) allopolyploids
c) aneuploids
d) bivalents
13) Nondisjunction can occur at either the first or second division of meiosis, XXY
individuals could arise from nondisjunction at the _____ meiotic division in the _____.
a) first, mother
b) second, mother
c) first, father
d) second, father
e) more than one of the above could give rise to XXY individuals
14) Histones and DNA have a strong attraction for each other because:
a) DNA is positively charged and histones are negatively charged
b) both DNA and proteins are hydrophobic
c) DNA is negatively charged and histones are positively charged
d) like substances share common charges
e) none of the above
15) In mammalian cells, replication proceeds:
a) unidirectionally
b) bidirectionally
c) unidirectionally from many origins
d) bidirectionally from only one origin
16) How many replication forks depart from an origin of replication?
a) one
b) two
c) three
d) four
e) none of the above
17) From DNA research, sites of transcription and therefore most of the genes along the
length of the chromosome appear to be found in:
a) heterochromatin
b) euchromatin
c) constitutive heterochromatin
d) centromeric regions
18) When a chromosomal rearrangement such as an inversion occurs placing a known
gene into a heterochromatic region, the gene’s expression:
a) will turn on
b) may be amplified
c) may cease
d) none of the above
19) In which of the following cases will a Barr body be seen?
a) XX
b) XY
c) XO
d) XXY
e) both a and d
20) Telomerase is not needed in bacterial DNA replication because bacteria
A) have a polymerase that can synthesize in the 3’-to-5’ direction
B) have plasmids that allow transitive polymerization of the telomeres
C) are able to tolerate the loss of chromosomal ends
*D) have circular chromosomes
E) do not replicate chromosomal DNA
PART B - Short answer. Please write clearly.
20) Match the region or item on the DNA replication diagram with the correct term from the
list below. (7 pts)
d____ Leading strand
c____ Lagging strand
a____ Origin
e____ RNA Primer
f____ Okazaki fragment
g____ Helicase
b____ Polymerase
22) Griffith found that smooth (S) forms of S. pneumoniae have a polysaccharide capsule
and rough (R) forms do not. Only S forms cause infection. Briefly describe how Griffith
demonstrated transformation using live R form and heat killed S form bacteria. (6 pts)
Answer: S heat killed does not yield infection; R live does not yield infection; S heat killed
plus R live = infection. R has been transformed by S.
21) When Meselson and Stahl performed the experiment which showed that replication is a
semiconservative process, they utilized E. coli, and various isotopes of nitrogen (15N and
14N). Explain briefly what their results would have been if DNA replicated conservatively (be
sure to describe the first two generations).(7 pts)
Answer: Following centrifugation, the first generation of replication would yield 2 bands- 15N
and 14N (no hybrid). The second generation would again result in the same pattern with no
hybrid pattern ever revealed.