Quiz 9
Ch 9
Name________________________
Remote # ____________
model of DNA, just as if you were climbing a
ladder. What parts of a nucleotide are your
feet touching as you climb?
a. the bases
b. the phosphates
c. the sugars and bases
d. the sugars and phosphates
e. the phosphates and bases
1. The sugars and phosphates in the
"backbone" of a DNA strand are held
together by ________.
a. covalent bonds
b. hydrogen bonds
c. ionic bonds
2. The two strands of a DNA double helix
are held together by ________.
a. covalent bonds between the sugars of
one nucleotide and the phosphates of the
adjacent nucleotide
b. hydrogen bonds between bases on
opposite DNA strands
c. ionic bonds between DNA and water
6. Human chromosomes range in size
dramatically, with the smallest
(chromosome Y) being many times smaller
than the largest (chromosome 1). What is
responsible for determining the size of a
chromosome?
a. the length of the DNA molecule in it
b. the amount of protein associated with it
c. the number of DNA molecules in it
3. Following replication, each DNA double
helix in a duplicated chromosome is
organized by proteins into a structure called
a ________.
a. chromatid
b. chromatin
c. chromosome
7. How does the information carried in the
sequence of bases in a DNA molecule
specify a characteristic such as eye color?
a. DNA makes a pigment that is stored in
the cells of the eye.
b. DNA encodes proteins that manufacture
eye-color pigments.
c. DNA can be blue, brown, or green,
depending on the amount in the cell.
4. Which of the following lists the correct
order of events in DNA replication?
a. Enzymes unwind the DNA double helix;
DNA polymerase makes two new DNA
strands complementary to the old ones; the
two DNA molecules wind up into a double
helix with one new strand and one old
strand.
b. Two DNA molecules wind up into a
double helix with one new strand and one
old strand; DNA polymerase makes two
new DNA strands complementary to the old
ones; enzymes unwind the DNA double
helix.
c. DNA polymerase makes the new DNA
strands complementary to the old ones;
enzymes unwind the DNA double helix; the
two DNA molecules wind up into a double
helix with one new strand and one old
strand.
8. Imagine that you are studying a newly
discovered bacterium from a hot springs in
Yellowstone National Park. When you
examine the nucleotide composition of this
organism, you find that 10% of the
nucleotides in its DNA are adenine. What
percentage of nucleotides are guanine?
Explain.
a. 10%, because A pairs with G
b. 90%, because 100% minus 10% equals
90%
c. 40%, because A pairs with T (accounting
for 20% of the bases), leaving 80% of the
nucleotides as G-C base pairs; half of 80 is
40.
5. DNA structure can be described as a
twisted ladder. Imagine you are climbing a
9. Select the pairings of nucleotides
determined by Chargaff's investigations.
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a. adenine-guanine / cytosine-thymine
b. deoxyribose-phosphate / adeninecytosine
c. thymine-adenine / guanine-cytosine
10. Prior to cell division what does a
"duplicated chromosome" contain?
a. two chromatids
b. two double helices of DNA held together
at their middle
c. a single double helix of DNA
d. Both the first and second answers are
correct.
11. Which of the following events occur
within a DNA replication bubble?
a. DNA polymerase helps to break
hydrogen bonds between complementary
base pairs.
b. DNA helicase attaches the phosphate of
a free nucleotide to the sugar of the
previous nucleotide in the daughter strand.
c. DNA helicase unwinds the double helix at
each replication fork within a replication
bubble.
d. none of the above
12. What is the approximate error rate for
DNA polymerase?
a. one error for every 100 bases added
b. one error for every 10,000 bases added
c. one error for every billion bases added
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