Final answer:
A cloning vector for use in bacteria must contain selectable markers, a single restriction site, and an origin of replication. These elements facilitate the identification, insertion, and replication of the foreign DNA within the bacterial host.
Step-by-step explanation:
Three features that a cloning vector for use in bacteria must contain are: selectable markers, a single restriction site, and an origin of replication.
Selectable markers, such as antibiotic resistance genes, allow scientists to identify and maintain transformants within the bacterial population. Cells that have taken up the cloning vector can survive in the presence of the antibiotic, permitting easy selection.
A single restriction site is critical as it allows the insertion of foreign DNA at a specific location without disrupting other parts of the vector. This ensures that only the target DNA is inserted and replicated.
The origin of replication is a DNA sequence that is necessary for the plasmid to replicate within the host bacterial cell. Without this, the cloning vector and the newly inserted DNA would not be able to multiply within the bacteria.