Molecular cloning is a method to prepare a recombinant DNA molecule, an extra-chromosomal circular DNA that can replicate autonomously within a microbial host. DNA ligation is commonly used in molecular cloning projects to physically join a DNA vector to a gene of interest. The ends of the DNA fragments can be blunt or cohesive and must contain monophosphate groups on the 5' ends. Following the mechanism described above, the covalent bonds are formed and a closed circular molecule is created that is capable of transforming a host bacterial strain. The recombinant plasmid maintained in the host is then available for amplification prior to downstream applications such as DNA sequencing, protein expression, or gene expression/functional analysis.
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