5. Which of the following is a physical mutagen? a) Nitrite b) Salt c) Radiation d) Stab wounds 6. rRNA is involved in: a) Transcription b) Translation c) Both of the above d) None of the above 7. Which of the following would you NOT want on a plasmid vector? a) Origin of Replication b) 2 Selectable Markers c) Restriction Site d) Operator 8. The biollistic method of transformation is typically used on: a) Plants b) Animals c) Bacteria d) All of the above

5. **c) Radiation** Radiation, such as X-rays and UV light, can cause physical damage to DNA, leading to mutations. Nitrite is a chemical mutagen, salt affects osmotic balance, and stab wounds cause physical trauma but don't directly alter DNA structure.<br /><br />6. **b) Translation** rRNA is a key component of ribosomes, the cellular machinery responsible for protein synthesis (translation). Transcription involves creating an RNA copy of DNA, a process rRNA is not directly involved in.<br /><br />7. **b) 2 Selectable Markers** While having one selectable marker is essential for identifying transformed cells, having two can complicate the process and isn't usually necessary. An origin of replication is crucial for plasmid reproduction, a restriction site is needed for inserting the gene of interest, and an operator can be useful for regulating gene expression. However, two selectable markers add unnecessary complexity.<br /><br />8. **a) Plants** The gene gun or biolistic method is commonly used to introduce DNA into plant cells by coating gold particles with DNA and then "shooting" them into plant tissue. While other methods exist for transforming animal and bacterial cells, the biolistic method is most effective for plants due to their cell walls.<br />