Final answer:
Plasmids are extrachromosomal DNA elements in bacteria that contain genes and replicate independently, sometimes more frequently than bacterial chromosomes. They are crucial for antibiotic resistance, genetic engineering, and can spread advantageous traits via horizontal gene transfer.
Step-by-step explanation:
Entities that contain one or more genes, replicate independently from the bacterial chromosome, and that are replicated by the same enzymes that replicate the host chromosome are known as plasmids. Plasmids are extra-chromosomal, double stranded, closed circular DNA molecules that can range in size and carry genetic information that is beneficial under certain conditions. They play significant roles in antibiotic resistance, the production of antibiotics, and are foundational tools in genetic engineering and biotechnology. High copy plasmids replicate many times within the cell, leading to a high number of copies, while low copy plasmids replicate fewer times.
These plasmids undergo a process of replication to produce daughter plasmids, which pass into daughter cells during cell division. Plasmid replication can occur at a different rate than the replication of the host's chromosomal DNA. In bacteria, plasmids can be exchanged through horizontal gene transfer (HGT), which can confer new, advantageous traits to the recipient bacterial cell such as virulence factors or antibiotic resistance. This exchange is significant, especially in clinical settings, as it enables rapid spread of such traits within bacterial populations.