What is molecular cloning and what are its basic steps?

Molecular cloning is the process of inserting a DNA fragment into a vector to replicate it in a host organism. The basic steps are: isolation of the DNA fragment of interest, digestion of both insert and vector with compatible restriction enzymes, ligation of insert into vector using DNA ligase, transformation of the construct into host cells (usually E. coli), selection of transformed cells using markers (antibiotic resistance), and screening for correct clones. The result is multiple identical copies of the DNA fragment that can be propagated indefinitely.