Plasmids are small circular dna molecules found in bacteria that replicate separately from chromosomes. why are plasmids essential for recombinant dna technology?

This is because DNA from a gene of interest can be inserted into a plasmid, then the modified plasmid can be inserted into a bacterial cell to make many copies of a gene of interest. Most plasmid vectors contain little more than the essential nucleotide sequences required for their use in DNA cloning: a replication origin, a drug-resistance gene, and a region in which exogenous DNA fragments can be inserted.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.