The Molecular Genetic Unit
STRUCTURE OF DNA
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Contributions of Scientists
o Meischer, Griffith*, Hammerling, Chargaff, Hershey and Chase*, Franklin, Watson and
Crick Who was responsible for discovering bacterial transformation?
Structure of a Nucleotide How do various nucleotides differ?
Structure of a DNA molecule What is meant by 5’ and 3’ ends of the molecule?
DNA REPLICATION
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Meselson and Stahl – Semiconservative Replication Why was only one band found after one round of
replication?
The process of DNA replication
o 6 enzymes and a binding protein What is the role of DNA gyrase? DNA ligase?
PCR Compare PCR to natural replication.
PROTEIN SYNTHESIS
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Contributions Garrod, Beadle and Tatum, Ingram
o (Gene – Protein relationship) What is meant by the “One gene-One polypeptide Hypothesis”?
Central Dogma Why is this so important to biology?
RNA and ribosomes Describe how the three types of RNA differ.
Transcription List the four steps of transcription.
Translation What is special about stop codons?
MUTATION
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Types and examples Why is it likely that most mutations are neutral?
Self Quiz
Chapter 4
Chapter 5
Chapter 6
all
eliminate 7
Do 1, 5, 7, 10 –13
Part A
1.
2.
Multiple Choice
The backbone of one strand of a DNA molecule starts
at a deoxyribose sugar and ends at a phosphate group.
This strand
a. is the coding strand.
b. is the template strand.
c. runs in the 3’ to 5’ direction.
d. runs in the 5’ to 3’ direction.
e. is unlikely to be transcribed into RNA.
The two strands of a DNA molecule are held together
by
a. covalent bonds.
b. ester linkage.
c. glycosyl linkage.
d. hydrogen bonds.
e. phosphodiester bonds.
b.
9.
False
Most of a human cell’s DNA is found in genes.
a. True
b. False
10. Many species have larger genomes (more base pairs)
than humans.
a. True
b. False
11. During replication, the nucleotides that are added
begin as a triphosphates.
a. True
b. False
Use the following options for questions 18 and 19.
3.
4.
5.
22% of a DNA molecule is found to be thymine.
What percentage of the molecule would be expected
to be guanine?
a. 16%
b. 22%
c. 28%
d. 44%
e. 56%
Aside from the nucleus, which other organelles in the
cell contains DNA?
a. Centrioles
b. Endoplasmic reticulum
c. Lysosomes
d. Chloroplasts
e. Ribosomes
Which of the following has an anticodon at one end
and an amino acid acceptor site at the other.
a. cRNA
b. mRNA
c. mtRNA
d. rRNA
e. tRNA
6.
Which of the following is combined with proteins and
built into two different sized subunits in the
nucleolus?
a. cRNA
b. mRNA
c. mtRNA
d. rRNA
e. tRNA
7.
The new strand in DNA replication and the messenger
RNA transcript are both built in the 5' to 3' direction.
a. True
b. False
8.
Each gene is one complete DNA molecule.
a. True
light
light
light
medium
heavy
medium
heavy
a
b
c
d
e
12. Meselson and Stahl cultured E. coli in cultures with
nitrogen-14 and nitrogen-15. First they grew the
bacteria for many generations in cultures with
nitrogen-15. When they isolated the DNA in density
gradient centrifugation, which of the above patterns
did they observe?
13. They then moved the bacteria to cultures that
contained only nitrogen-14 and allowed one cycle of
reproduction. When they isolated the DNA this time,
what banding pattern did they find?
14. This experiment confirmed which of the following
ideas?
a. DNA requires nitrogen for replication.
b. DNA replication is conservative.
c. DNA replication is semi-conservative.
d. Transcription is semi-conservative.
e. None of the above.
15. Which of the following enzymes is responsible for
adding nucleotides to the growing DNA strand?
a. DNA gyrase
b. DNA ligase
c. DNA polymerase I
d. DNA polymerase III
e. RNA primase
16. Which of the following in PCR performs the same
function as RNA primase?
a. Heat
b. Cooling
c. RNA polymerase
d. Primers
e. Taq polymerase
Part B
1.
2.
3.
4.
5.
6.
17. One way that eukaryote replication differs from
prokaryote replication is
a. eukaryote replication is much simpler.
b. eukaryote replication occurs much faster.
c. eukaryote replication starts at many
places in the genome.
d. eukaryote replication has been studied
more and is better understood.
Description Questions
List 3 key steps in the science that placed DNA at the center of modern biology.
Describe the process of DNA replication.
Where does replication occur in the cell cycle?
How is transcription similar to replication?
Describe the role of tRNA in protein synthesis.
How does the lac operon work?
Part C
Explanation Questions
7. Compare the processes of DNA replication and transcription.
8. Why is most of our understanding of molecular genetics based on experiments with
bacteria?
9. DNA and the Central Dogma are at the center of modern biology. Describe 3 key
contributions by scientists and how they improved our understanding.
1c
2d
3c
15d
16b
17c
4d
5e
6d
7a
8b
9b
10a
11a
12c
13b
14c