Final answer:
In a single bacterial cell, the number of plasmids can range from one to several hundreds, with some cells having 10 to 50 copies. These plasmids are extra-chromosomal DNA that can carry genes beneficial to the host, such as antibiotic resistance, and are important in genetic engineering.
Step-by-step explanation:
In a single bacterial cell, the number of plasmids can vary widely. Plasmids are extra-chromosomal genetic elements that are double-stranded, closed circular DNA molecules. The amount of plasmids in each cell can range from a single copy to several hundreds. They can be as small as 1 kilobase (kb) or as large as 200 kb. A typical bacterial cell may carry one or more plasmids, with some cells possibly having 10 to 50 copies. These plasmids may contain genes that confer benefits such as antibiotic resistance or production of antibiotics to the host bacteria.
Bacteriophage can be used as vectors to clone larger DNA inserts due to the small size of plasmids, which are limited to carrying inserts that rarely exceed 1000 base pairs. The role of plasmids is essential in both natural bacterial processes, such as horizontal gene transfer, and in biotechnological applications like genetic engineering, where they are used to transport genes across cells.