BIOS 242 Week 3 Exam 1
Week 3 · Exam 1 · Question Review
Question 5 Answers: A – D
Bacteria and fungi are:
A Not infected by viruses
B Host cells of viruses ✓
C Host cells of viroids
D Host cells of prions
✓ Correct Answer: B – Host cells of viruses
Explanation: Bacteria can be infected by bacteriophages (viruses that infect bacteria), and fungi are also
susceptible to viral infections (mycoviruses). Both therefore serve as host cells for viruses.
The viral genome may be composed of:
, Question 6 Answers: A – D
A Single-stranded DNA
B Single-stranded RNA
C Double-stranded RNA
D All these options ✓
✓ Correct Answer: D – All these options
Explanation: Viral genomes are extraordinarily diverse. They may consist of ssDNA (e.g., parvoviruses), ssRNA
(e.g., coronaviruses), dsDNA (e.g., herpesviruses), or dsRNA (e.g., reoviruses), making 'All these options' correct.
Ionizing radiation induces mutations in DNA by:
, Question 7 Answers: A – D
A Removing amine groups from some bases
B Cross-linking adjacent pyrimidines
C Forming charged molecules that cause breaks in DNA ✓
D Causing frameshifts due to the insertion of nucleotides
✓ Correct Answer: C – Forming charged molecules that cause breaks in DNA
Explanation: Ionizing radiation (e.g., X-rays, gamma rays) generates free radicals and reactive ions that directly
break phosphodiester bonds in the DNA backbone, leading to single- and double-strand breaks.
________ are pieces of extrachromosomal DNA that can replicate independently.
, Question 8 Answers: A – D
A Pili
B Fimbriae
C Flagella
D Plasmids ✓
✓ Correct Answer: D – Plasmids
Explanation: Plasmids are small, circular (occasionally linear) dsDNA molecules found mainly in bacteria. They
possess their own origin of replication and can replicate autonomously, often encoding advantageous traits such
as antibiotic resistance.
Week 3 · Exam 1 · Question Review
Question 5 Answers: A – D
Bacteria and fungi are:
A Not infected by viruses
B Host cells of viruses ✓
C Host cells of viroids
D Host cells of prions
✓ Correct Answer: B – Host cells of viruses
Explanation: Bacteria can be infected by bacteriophages (viruses that infect bacteria), and fungi are also
susceptible to viral infections (mycoviruses). Both therefore serve as host cells for viruses.
The viral genome may be composed of:
, Question 6 Answers: A – D
A Single-stranded DNA
B Single-stranded RNA
C Double-stranded RNA
D All these options ✓
✓ Correct Answer: D – All these options
Explanation: Viral genomes are extraordinarily diverse. They may consist of ssDNA (e.g., parvoviruses), ssRNA
(e.g., coronaviruses), dsDNA (e.g., herpesviruses), or dsRNA (e.g., reoviruses), making 'All these options' correct.
Ionizing radiation induces mutations in DNA by:
, Question 7 Answers: A – D
A Removing amine groups from some bases
B Cross-linking adjacent pyrimidines
C Forming charged molecules that cause breaks in DNA ✓
D Causing frameshifts due to the insertion of nucleotides
✓ Correct Answer: C – Forming charged molecules that cause breaks in DNA
Explanation: Ionizing radiation (e.g., X-rays, gamma rays) generates free radicals and reactive ions that directly
break phosphodiester bonds in the DNA backbone, leading to single- and double-strand breaks.
________ are pieces of extrachromosomal DNA that can replicate independently.
, Question 8 Answers: A – D
A Pili
B Fimbriae
C Flagella
D Plasmids ✓
✓ Correct Answer: D – Plasmids
Explanation: Plasmids are small, circular (occasionally linear) dsDNA molecules found mainly in bacteria. They
possess their own origin of replication and can replicate autonomously, often encoding advantageous traits such
as antibiotic resistance.
