Practice questions for BIO 340 (Dr. Holechek’s Exam 3)
Note: We will be discussing these questions during office hours on
Tuesday, February 20 from 9:30 am - 11:00 am. To join the meeting:
https://asu.zoom.us/j/85451466686
1. Which activity of DNA polymerase is responsible for its ability to proofread newly
synthesized DNA?
The 3’->5’ exonuclease activity
2. How many mutations would you expect to see in the human genome (6 x 10 9) if mismatches
could not be repaired? Hint: Because of tautomeric shift-induced mismatches, DNA replication
inherently can be no more accurate than 10-4 mutations/base pair.
10^-4= 1/10^4 1 mutation per 10,000 base pairs
(6*10^9)/10^4
=6*10^5
=600,000
3. Proofreading removes approximately 99% of mismatches before DNA replication moves on.
After proofreading what is the mutation rate for DNA replication in humans?
=1% of 10^-4
1/10^4 * 1/100 1/10^4 * 1/10^2 = 1/10^6
4. Each of the five DNA strands below (A-E) are slowly heated. Which strand will melt first?
Hint: Think about the number of hydrogen bonds between A and T vs G and C.
A. 5’-ATATCGATTA-3’
3’-TATAGCTAAT-5’
B. 5’-ACGGATGCAC-3’
3’-TGCCTACGTG-5’
C. 5’-GCGCCCGGCG-3’
3’-CGCGGGCCGC-5’
D. 5’-TTCGAGTGAA-3’
3’-AAGCTCACTT-5’
E. 5’-CGCCGGATGC-3’
3’-GCGGCCTACG-5’
, 5. What is the sequence of the right hand strand of the DNA shown below?
Hint: The figure below can help, think about where the 5’ phosphate and the 3’ hydroxyl
groups are located with respect to the pentose sugar.
A. 5’ ACTG 3’
B. 5’ TGAC 3’
C. 3’ CAGT 5’
D. 3’ TGAC 5’
E. 5’ TGAC 3’
6. The two oligonucleotides below are allowed to anneal and a set of sequencing reactions are
performed. What will the sequencing gel of the first 6 nucleotides added to the DNA look like?
Hint: Think about directionality and the concept that DNA strands are antiparallel.
5’ ATCCTGGACACTGTACCATCGGTACCAATCACAGGTCCTTACAGT 3’
5’ CAGTGTC 3’ This is the primer
Step 1: The primer needs to be rewritten in the right direction in coorespondance to the DNA
strand above. 3’ CTGTGAC 5’
Step 2: You need to transcribe the primer to find the complimentary sequence within the DNA
strand. GACACTG, find this sequence in the DNA code and underline it.
Note: We will be discussing these questions during office hours on
Tuesday, February 20 from 9:30 am - 11:00 am. To join the meeting:
https://asu.zoom.us/j/85451466686
1. Which activity of DNA polymerase is responsible for its ability to proofread newly
synthesized DNA?
The 3’->5’ exonuclease activity
2. How many mutations would you expect to see in the human genome (6 x 10 9) if mismatches
could not be repaired? Hint: Because of tautomeric shift-induced mismatches, DNA replication
inherently can be no more accurate than 10-4 mutations/base pair.
10^-4= 1/10^4 1 mutation per 10,000 base pairs
(6*10^9)/10^4
=6*10^5
=600,000
3. Proofreading removes approximately 99% of mismatches before DNA replication moves on.
After proofreading what is the mutation rate for DNA replication in humans?
=1% of 10^-4
1/10^4 * 1/100 1/10^4 * 1/10^2 = 1/10^6
4. Each of the five DNA strands below (A-E) are slowly heated. Which strand will melt first?
Hint: Think about the number of hydrogen bonds between A and T vs G and C.
A. 5’-ATATCGATTA-3’
3’-TATAGCTAAT-5’
B. 5’-ACGGATGCAC-3’
3’-TGCCTACGTG-5’
C. 5’-GCGCCCGGCG-3’
3’-CGCGGGCCGC-5’
D. 5’-TTCGAGTGAA-3’
3’-AAGCTCACTT-5’
E. 5’-CGCCGGATGC-3’
3’-GCGGCCTACG-5’
, 5. What is the sequence of the right hand strand of the DNA shown below?
Hint: The figure below can help, think about where the 5’ phosphate and the 3’ hydroxyl
groups are located with respect to the pentose sugar.
A. 5’ ACTG 3’
B. 5’ TGAC 3’
C. 3’ CAGT 5’
D. 3’ TGAC 5’
E. 5’ TGAC 3’
6. The two oligonucleotides below are allowed to anneal and a set of sequencing reactions are
performed. What will the sequencing gel of the first 6 nucleotides added to the DNA look like?
Hint: Think about directionality and the concept that DNA strands are antiparallel.
5’ ATCCTGGACACTGTACCATCGGTACCAATCACAGGTCCTTACAGT 3’
5’ CAGTGTC 3’ This is the primer
Step 1: The primer needs to be rewritten in the right direction in coorespondance to the DNA
strand above. 3’ CTGTGAC 5’
Step 2: You need to transcribe the primer to find the complimentary sequence within the DNA
strand. GACACTG, find this sequence in the DNA code and underline it.
