Gene clone

DNA Cloning Summary

  • Definition: A molecular biology technique that creates multiple identical copies of a specific piece of DNA, such as a gene.

  • Process:

    1. Insertion: A target gene is inserted into a plasmid (a circular piece of DNA).

    2. Transformation: The plasmid is introduced into bacteria, which are then selected using antibiotics.

    3. Replication: Bacteria carrying the plasmid reproduce and replicate the plasmid DNA.

    4. Protein Production: Sometimes, bacteria are induced to express the gene and produce a protein (e.g., insulin).

  • Key Concepts:

    • DNA cloning is not about cloning whole organisms but rather copying segments of DNA.

    • Restriction enzymes cut DNA at specific sequences, allowing for the creation of recombinant DNA when combined with plasmids using DNA ligase.

    • Successful transformation of bacteria is confirmed through antibiotic resistance; only the bacteria that took up the plasmid will survive.

    • Applications of DNA cloning include biopharmaceuticals, gene therapy, and gene analysis.

  • Applications:

    • Making proteins like insulin for medical use

    • Providing a normal gene version for gene therapy in genetic disorders

    • Building recombinant genes for research purposes.

Diagram depicting restriction digestion and ligation in a simplified schematic. We start with a circular bacterial plasmid and a target gene. On the two ends of the target gene are restriction sites, or DNA sequences recognized by a particular restriction enzyme. In the plasmid, there is also a restriction site recognized by that same enzyme, right after a promoter that will drive expression in bacteria. Both the plasmid and the target gene are (separately) digested with the restriction enzyme. The fragments are purified and combined. They have matching "sticky ends," or single-stranded DNA overhangs, so they can stick together. The enzyme DNA ligase joins the fragments with matching ends together to form a single, unbroken molecule of DNA. This produces a recombinant plasmid that contains the target gene.