Download ANSWERS TO REVIEW QUESTIONS

ANSWERS TO REVIEW QUESTIONS
CHAPTER 9
1. A pentose sugar, nitrogenous base and phosphate group
2. The nitrogenous bases in purines have a two-ringed structure while those in pyrimidines have
a single-ring structure.
3. DNA must be replicated so that a complete set of genetic instructions is passed to daughter
cells when a cell divides.
4. Such a molecule would bulge where purines paired with each other, yet be narrow where
pyrimidines pair with each other.
5. The nucleotide base sequence encodes information.
6. One end of a strand of nucleotides has a phosphate group attached to the 5' carbon of
deoxyribose. The other end has a hydroxyl group attached to the 3' carbon. Phosphodiester
bonds (which bind the sugar-phosphate backbone) form between the 3' OH of the nucleotide
chain and the 5' phosphate of an incoming nucleotide. Thus the chain grows in the 5' to 3'
direction. The two strands are antiparallel  one strand is 5'-3' and the other is 3'-5'.
7. 1 E, 2 C, 3 D, 4 B, 5 A
8. Helicases, primase, DNA polymerase, ligase
9. They are organized into nucleosomes, which then are further compacted into chromatin.
10. Histone protein, nucleosome, chromatin
11. Helicase unwinds DNA and binding proteins stabilize it.
12. Strands separate and are held apart. Primase makes RNA primer. DNA polymerase adds
DNA bases to RNA primer. Proofreading repair. Continuous on one strand only. RNA primers
removed. Ligase seals sugar-phosphate backbone.
13. Because the two strands are antiparallel
14. RNA forms a primer to which DNA polymerase can bind.
15. Hershey and Chase showed that DNA is the genetic material and protein is not. Meselson
and Stahl showed that DNA replication is semiconservative, but not conservative or
dispersive.
16. Downloading a document is similar to DNA replication because the original information
persists, but is dissimilar in that not all information is reproduced and downloading is not
based on complementarity.
ANSWERS TO APPLIED QUESTIONS
1. The sugar-phosphate backbone of replicating DNA cannot attach.
2. Primase, DNA polymerase, helicase, binding proteins, and ligase are required for DNA
replication. These are all proteins.
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3. Lacking DNA polymerase makes life impossible, because cells cannot divide.
4. a. A G C T C T T A G A G C T A A
b. G G C A T A T C G G C C A T G
c. T A G C C T A G C G A T G A C
5. Answers vary. Determining the structure of DNA led to discoveries of the mechanism of
heredity, and applies to all species. Sequencing the human genome applies only to us and
has so far helped researchers more than it has led to treatments.
6. The film GATTACA depicts a society based on knowing genome sequences. Crime television
shows such as the Law and Order and CSI programs regularly use forensic DNA testing, which
compares one or two dozen selected sites in the human genome to rule out suspects.
7. Several indigenous peoples have objected to DNA collected for study of one trait that is
subsequently used to study another, without further permission. This happened to the Havasupai
Indians who gave DNA for diabetes testing, which was then used in a schizophrenia study. DNA
testing can help people locate relatives, such as in paternity tests.
8. A gene is a segment of DNA containing the information to specify a sequence of amino acids in
a protein.
ANSWERS TO WEB ACTIVITIES
1. a. Opinion. The yellow sea horse, so we can learn how to enable males to carry fetuses!
b. Answers vary. One example might be: Yes, to protect all endangered species.
c. Stored DNA is not enough to regenerate an animal. Two copies of the entire genome
must be in an egg that continues development. Stored DNA might be methylated in ways
that block the expression of some genes necessary for early development.
2.
Position
61290
is
TCTCTTCTTTTAGTTCTTCG
AGAGAAGAAAATGAAGAAGC.
The
complement
is
ANSWERS TO CASE STUDIES AND RESEARCH RESULTS
1. a. Germline transmission of the virus
b. It is universal
2. No, because the phosphorus in DNA does not encode information.
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