Question

The presence of a specific plasmid in a bacterial cell may be determined if the plasmid _

-contains pieces of a viral genome
-contains a selectable marker
-is a vector
-is exceptionally large
- All of the above are correct

Answer 1

The presence of a plasmid in a bacterial cell is often determined by the existence of a selectable marker, such as an antibiotic resistance gene, which allows for the identification of bacterial transformants.

Step-by-step explanation:

The presence of a specific plasmid in a bacterial cell can be determined if the plasmid contains a selectable marker. Selectable markers, such as antibiotic resistance genes, allow researchers to identify transformants that have incorporated the plasmid by growing the bacteria on medium containing the corresponding antibiotic. Only bacterial cells that have taken up the plasmid and express the resistance gene will survive and produce colonies.

Plasmids are often used as vectors for molecular cloning due to their ability to independently replicate within the bacterial host, allowing the inserted foreign DNA, also known as a transgene, to be copied and studied in isolation. While plasmids can contain pieces of viral genome or be exceptionally large, the presence of a selectable marker is particularly crucial for determining if a plasmid has been successfully integrated into a bacterial cell.