Download Homework 3.1 CHEM151: Biochemistry I Prof. Tsai Page 1 of 4 1

Homework 3.1
CHEM151: Biochemistry I
Prof. Tsai
1. Give the names of the four nucleotides found in a DNA molecule.
2. What are the two main differences between DNA and RNA?
3. What is the difference between a purine and a pyrimidine?
4. If you are given the writhing number (W) to be 10 and the linking number (L) to be 2, what is the
twisting number (T)?
5. What is the difference between Type I and Type II topoisomerases? (2 points)
6. Will a supercoiled DNA molecule migrate faster or slower in gel electrophoresis when compared to
a relaxed DNA molecule?
7. What are the roles of DNA & RNA in the “The Central Dogma in Molecular Biology”?
8. Is the sugar phosphate backbone of the DNA molecule positively charged or negatively charged?
9. Why does the absorbance increase when nucleic acids are denatured.
10. Calculate the number of base pairs are required to span a 15Å stretch for A, B, & Z forms of DNA.
11. Mark the following either True (T) or False (F):
a. Only 20 different amino acids are found in proteins.
b. High pH is used to hybridize two complementary DNA strands to form a double-stranded
molecule.
c. 5' endonucleases cleave nucleotides sequentially from the 5' end of a DNA fragment.
d. A G:C base pair is more stable than an A:T base pair.
e. DNA is made up of a sugar-phosphate polymer containing nitrogenous bases.
f. Some viruses can reverse transcribe RNA to DNA.
g. During replication, DNA is synthesized in a 5' to 3' direction.
h. During transcription, the template DNA strand is read in a 5' to 3' direction.
i. During transcription, RNA is synthesized in a 5' to 3' direction.
12. Double-stranded nucleic acid helices:
a) are always left-handed
b) do not have a handedness.
c) are always right-handed.
d) can be either right- or left-handed
Page 1 of 4
Homework 3.1
CHEM151: Biochemistry I
Prof. Tsai
13. The following is a picture of the base 2,6-diaminopurine (DAP). If this base were incorporated into a
nucleic acid, what natural base would it pair with?
a)A
b)C
c) T or U
d)U
e)T
14. Which of the following statements about DNA replication in prokaryotes is false?
a) DNA synthesis proceeds along both strands at the same time
b) DNA synthesis proceeds in both directions from an origin simultaneously.
c) Leading strand synthesis occurs in short bursts, creating a series of fragments.
d) A polymerase complex can be found at the replication fork
15. You are carrying out a restriction digest on a DNA sample. One indication that the DNA is circular
is:
a) No matter which enzyme you use, the fragments all add up to the same overall length.
b) You cut with an enzyme that cuts the DNA twice, and you get two fragments.
c) You cut with an enzyme that cuts the DNA twice, and you get three fragments.
d) When you cut the DNA with different enzymes, the fragments add up todifferent overall
lengths
16. Which of the following is an example of correctly paired bases found in RNA?
A. A---G, C---T
B. A---G, C---U
C. A---U, C---G
D. A---T, C---G
17.
All of the following are unique DNA structures EXCEPT:
A. palindrome
B. hairpin
C. cruciform
D. bulge
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Homework 3.1
18.
CHEM151: Biochemistry I
Prof. Tsai
Which double strand of DNA is most stable and will denature at the highest temperature?
A. CGCGGUUAUCG
GCGCCAAUAGC
B. TTAATGATCATA
AATTACTAGTAT
C. CCGCGGACGGA
GGCGCCTGCCT
D. UAAUUACUAGA
AUUAAUGAUCU
19.
All of the following are types of DNA mutations EXCEPT:
A. supercoiling
B. deanimation
C. depurination
D. formation of pyrmidine dimers
20.
Match the nuclease with the appropriate action:
A.
B.
C.
D.
DNAase
Exo
Endo
RNAase
i. cleaves at the end
ii. Only acts on DNA
iii. Only acts on RNA
iv. Cleaves at an internal location
21.
DNA is more stable than RNA because:
A. polymerization can occur at the free 3’ OH end.
B. DNA can form phosphodiester bonds while RNA cannot.
C. DNA is missing a 2’ OH group that prevents it from undergoing base hydrolysis.
D. DNA undergoes keto-enol tautomeric shifts.
22.
All of the following are true EXCEPT:
A. adenosine and thymine form 3 hydrogen bonds when base paired
B. base pairs have major and minor grooves
C. B is the most common form of DNA
D. The Z form of DNA has the largest helix rise per base pair
23.
Which of the following contribute to stability of nucleic acid structures?
A. hydrophobic interactions
B. ionic interactions
C. base pairing
D. all of the above
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Homework 3.1
CHEM151: Biochemistry I
Prof. Tsai
24.
All of the following are consistent with “The Central Dogma in Molecular Biology” EXCEPT:
A. Ribosomes transcribe RNA in the cytoplasm of the cell.
B. DNA is transcribed 5’ end to 3’ end.
C. Genetic information is stored in DNA.
D. Proteins/gene products are translated from mRNA.
25.
Put the following steps for plasmid transformation in sequential order:
A. The plasmid is cleaved at a specific site by a restriction endonuclease such as ECoRI.
B. Individual colonies are plated on two different mediums that will determine which cells
have incorporated the correct plasmid of interest versus an unchanged plasmid.
C. Foreign DNA of interest is ligated into the cleaved plasmid.
D. Plasmids are inserted into E.coli cells and grown on agar plates containing one specific
antibiotic to see which cells have taken up the plasmid.
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