DNA Transformation Notes

DNA Transformation Process

• DNA transformation involves the transfer of naked DNA into a recipient cell.

Steps in DNA Transformation

• Initial Binding: Double-stranded donor DNA binds to specific receptors on the surface of a competent cell.
• DNA Degradation and Entry: One strand of the donor DNA is degraded by nucleases.
  • The remaining single-stranded donor DNA enters the cell.
• Homologous Recombination: The single-stranded donor DNA pairs with a homologous region on the recipient DNA.
  • Integrated into the recipient genome through a breakage and reunion mechanism called homologous recombination.
• Mismatch Repair: If there are differences between the nucleotide sequences of the donor and recipient DNAs, the mismatch repair system is activated.
  • The repair system removes either the donor or the recipient strand.
  • Replaces it with the complementary sequence.
  • Since either strand may be repaired, some cells contain the new donor DNA, and others have the original DNA sequences.
• Selection of Transformants: In the laboratory, cells are plated on selective media, allowing only the transformants to grow.

Homologous Recombination

• A breakage and reunion mechanism.

Mismatch Repair System

• Activated when there are differences between the nucleotide sequences of the donor and recipient DNAs.
• Either the donor or the recipient strand is removed and replaced with the complementary sequence.
• The outcome is that some cells contain the new donor DNA, and others have the original DNA sequences.

Selective Media

• Cells are plated on selective media.
• Only the transformants (cells that have successfully incorporated the donor DNA) will grow.