What is the difference between transformation and transfection?

Transformation: introduction of foreign DNA into prokaryotic (bacterial) cells. Bacteria take up DNA from their environment (natural competence) or are made artificially competent (heat shock with CaCl₂, electroporation). Transfection: introduction of foreign DNA into eukaryotic (animal) cells. Methods include liposome-mediated transfection, electroporation, viral vectors, microinjection. The term 'transduction' is used when a bacteriophage carries DNA into bacteria.

What is insertional inactivation? How is it used to identify recombinants?

When foreign DNA is inserted into the lacZ gene of a plasmid (like pUC19), the gene is disrupted and cannot produce functional β-galactosidase. In presence of X-gal substrate: Non-recombinants (intact lacZ) cleave X-gal → blue product → blue colonies. Recombinants (disrupted lacZ) cannot cleave X-gal → no colour → white colonies. Scientists pick white colonies as they carry the recombinant plasmid with the insert. All colonies grow on ampicillin plates (selection marker) but only recombinants are white.

Recombinant DNA Technology, Restriction Enzymes, and Cloning

Biotechnology — Principles and Processes • Class 12 Biology • NCERT • CBSE

Restriction enzymes cut DNA at palindromic sequences. Cloning vector (plasmid/phage) carries foreign DNA into host. Steps: isolation → restriction digestion → ligation → transformation → selection. PCR amplifies DNA in vitro.

Key Formulas

PCR copies after n cycles: 2ⁿ
Palindrome: reads same on both strands 5'→3'

Frequently Asked Questions

What is the difference between transformation and transfection?: Transformation: introduction of foreign DNA into prokaryotic (bacterial) cells. Bacteria take up DNA from their environment (natural competence) or are made artificially competent (heat shock with CaCl₂, electroporation). Transfection: introduction of foreign DNA into eukaryotic (animal) cells. Methods include liposome-mediated transfection, electroporation, viral vectors, microinjection. The term 'transduction' is used when a bacteriophage carries DNA into bacteria.
What is insertional inactivation? How is it used to identify recombinants?: When foreign DNA is inserted into the lacZ gene of a plasmid (like pUC19), the gene is disrupted and cannot produce functional β-galactosidase. In presence of X-gal substrate: Non-recombinants (intact lacZ) cleave X-gal → blue product → blue colonies. Recombinants (disrupted lacZ) cannot cleave X-gal → no colour → white colonies. Scientists pick white colonies as they carry the recombinant plasmid with the insert. All colonies grow on ampicillin plates (selection marker) but only recombinants are white.

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