Biology: Life on Earth 7e
Student Self Test Questions and Answers
Chapter 9: DNA: The Molecule of Heredity
Self Test
1. Except for eggs and sperm, different cells in your body are different because they have different ________. (Level
1)
a. DNA
b. chromosomes
c. proteins
2. The sugars and phosphates in the "backbone" of a DNA strand are held together by ________.
a. covalent bonds
b. hydrogen bonds
c. ionic bonds
3. 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
4. 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
5. Mutations are changes in the________.
a. sugar-phosphate backbone of DNA
b. base-pairing rules for DNA
c. sequence of bases in DNA
6. 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.
7. DNA structure can be described as a twisted ladder. Imagine you are climbing a 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
Biology: Life on Earth 7e
Student Self Test Questions and Answers
8. 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
9. 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.
10. 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.
11. You might think that the amount of DNA should increase with the degree of complexity of an organism. If so, the
total amount of DNA in a cell from an organism would be an indicator of how complex the organism is. However,
organisms such as pumpkins and salamanders have more DNA than do humans, even though we are actually more
complex. Propose an explanation.
a. Salamanders and pumpkins have more DNA and therefore must encode more information in
their DNA.
b. Some of the DNA in an organism may not encode anything; salamanders and pumpkins have
more of this noncoding DNA.
c. Salamanders and pumpkins produce more types of proteins than do humans and therefore need
more DNA to encode those proteins.
12. How can a cell, killed by heat in order to render it harmless, somehow still act to transform a second strain of
bacterium from a noninfectious form into a disease carrier (i.e., a pathogen)?
a. The second (noninfectious) strain of bacterium was changed into a disease carrier (i.e.,
pathogen) by something from the heat-killed cell.
b. The heat-killed cell wasn't really dead.
c. The second (noninfectious) strain spontaneously mutated into a deadly pathogen.
d. Both the second and third answers above are correct.
13. Select the pairings of nucleotides determined by Chargaff's investigations.
a. adenine-guanine / cytosine-thymine
b. deoxyribose-phosphate / adenine-cytosine
c. thymine-adenine / guanine-cytosine
14. To what does the phrase "ladder-like appearance" refer when considering the structure of DNA?
a. double helix
b. complementary base pairs (e.g., adenine and thymine) that are joined by hydrogen bonds
2
Biology: Life on Earth 7e
Student Self Test Questions and Answers
c. DNA strand (i.e., "polymer") orientation
d. the complementary base pairs as rungs and the sugar-phosphate backbone as the rails
15. 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.
16. 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
17. Which of the following options would result from the actions of DNA polymerase during DNA replication?
a. Two DNA polymerase molecules act to synthesize a long continuous daughter DNA strand from
each parental strand; ligase is not needed.
b. Two DNA polymerase molecules act to synthesize a short segment of daughter DNA strand from
each parental strand; ligase is used to connect these short segments of both daughter strands.
c. Two DNA polymerase molecules act to synthesize daughter DNA strands: one via a long
continuous strand that moves in the same direction as the helicase, and a second polymerase
synthesizes short segments of DNA that must be joined by ligase.
d. none of the above
18. Chromosomes are made of which of the following molecules?
a. protein
b. DNA
c. genes
d. protein and DNA
e. protein, DNA, and genes
19. Why did many scientists have trouble believing that DNA could be the carrier of genetic information?
a. DNA is a monotonous molecule with the same four nucleotides repeating over and over again.
b. DNA has only four nucleotides, which seemed too few to encode the vast array of hereditary
traits of organisms.
c. Protein structure is innately more suited to carrying hereditary information.
20. How many times is a cell's DNA replicated before it divides?
a. once
b. twice
c. three times
21. 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
3
Biology: Life on Earth 7e
Student Self Test Questions and Answers
22. What is the approximate error rate for DNA replication?
a. one error for every thousand nucleotides
b. one error for every million nucleotides
c. one error for every billion nucleotides
23. Which of the following can cause errors to accumulate in DNA?
a. high levels of metabolic activity
b. ultraviolet light
c. cold temperatures
d. None of the above are correct.
24. Which of the following can be caused by ultraviolet radiation in sunlight?
a. Adjacent thymines become linked together.
b. The DNA molecule is degraded from each end.
c. DNA molecule becomes fragmented.
d. All of the above can happen.
25. What is the name Watson and Crick gave to the physical structure of DNA? ____________________
19. ____________________ is the enzyme that splits the two original strands of DNA during replication.
20. Rosalind Franklin and Maurice Wilkins used ____________________ to help discover the physical structure of
DNA.
21. As a DNA strand is duplicated, the newly created strand is called ____________________ to the original strand.
22. ____________________ light is one of the listed causes for skin cancer (melanoma).
23. Under normal circumstances, adenine will only be paired with ____________________ during DNA replication.
4
Biology: Life on Earth 7e
Student Self Test Questions and Answers
24. The four DNA nucleotides are subtly different, yet each is composed of similar subunits. On the diagram below,
identify the three parts of a nucleotide.
5
Biology: Life on Earth 7e
Student Self Test Questions and Answers
25. DNA is replicated within the nucleus. Enzymes are required to do this. Label the enzyme needed for each spot
indicated on the image below.
30. The process by which a parent cell that is going to divide synthesizes an exact copy of its DNA is known as
_______________.
27. In Griffith's experiments, heating the S-strain bacteria killed them, but did not completely destroy their
___________________.
28. It is not the number of different nucleotides, but their __________________ that is important in the ability of DNA
to code for all the variability of organisms.
6