DNA Transcription, Translation, and Biotech Applications

Posted on Nov 27, 2024 in Biology

Transcription

Step 1: A copy of DNA corresponding to a gene’s nucleotide sequence is transcribed into RNA. RNA polymerase uses one strand of DNA as a template, synthesizing a complementary RNA molecule. Ribonucleotide triphosphates are used as precursors, and no primer or nuclease activity is needed.

  • Initiation: The gene’s promoter region indicates where mRNA synthesis begins and which DNA strand to transcribe. RNA polymerase binds to the promoter with a protein subunit, initiating transcription and opening the DNA double helix. Synthesis proceeds in the 5′ to 3′ direction.
  • Elongation: RNA polymerase moves along the DNA, unwinding the double helix and synthesizing the mRNA chain in the 5′ to 3′ direction. The RNA chain is released from the DNA template, and RNA polymerase facilitates double helix reformation.
  • Termination: RNA polymerase continues adding nucleotides until it reaches a termination signal. The polymerase detaches from the DNA, and the synthesized RNA is released as a single strand.

Translation (Protein Biosynthesis)

Translation converts the nucleotide language of mRNA into the amino acid language of proteins. Three mRNA bases form a codon. Each codon corresponds to a tRNA molecule carrying a specific amino acid via its anticodon. The genetic code is universal (same for all organisms) and degenerate (multiple codons can code for the same amino acid).

  • Amino Acid Activation: Each amino acid binds to its specific tRNA (anticodon). This reaction is catalyzed by aminoacyl-tRNA synthetase enzymes and requires ATP.
  • Initiation: mRNA binds to the small ribosomal subunit. The mRNA’s 5′ end has a leader sequence that is not translated. The initiator codon enters the peptidyl (P) site of the ribosome, and the next codon is positioned in the acceptor (A) site.
  • Elongation: tRNA binds to the A site, linking its amino acid to the growing polypeptide chain. The ribosome then translocates to the next codon on the mRNA in the 3′ direction.
  • Termination: Termination sequences are recognized by termination factors. The polypeptide chain is released from the last tRNA, and the ribosomal subunits separate.

Methods of Inserting a Foreign Gene into a Plant

  • Physico-chemical methods: Direct transformation of protoplasts (plant cells without walls) by electroporation.
  • Biolistics: Bombarding plant cells with DNA-coated microparticles using a gene gun, allowing DNA to enter the cells without removing the cell wall.
  • Agrobacterium strains: Bacteria of the genus Agrobacterium naturally produce tumors in plants by transferring DNA from a plasmid. For transgenic plants, the tumor-inducing genes are removed from the plasmid and replaced with the desired genes.

Biotechnology Applications

Biotechnology is the application of organisms, systems, and biological processes for producing goods and services.

  • Food Industry: Alcoholic fermentation, lactic acid fermentation (used in dairy to curdle milk).
  • Pharmaceutical Industry: Production of antibiotics, vaccines, serums, proteins, and hormones.
  • Environment: Bioremediation (contaminant removal by microorganisms), wastewater treatment, biodegradation of waste, industrial waste removal, biodegradation of oil, and production of biodegradable microbial composites.

Genetic Engineering

Genetic engineering encompasses techniques to modify the genomes of living organisms.

  • Medicine: Production of human substances by bacteria (insulin, growth hormone), vaccine development (hepatitis B), clinical diagnosis of hereditary diseases, gene therapy, cancer therapy, and immunological therapy.
  • Agriculture: Transgenic varieties of maize and tomato, nitrogen-fixing plants, and production of valuable substances by transgenic plants.
  • Livestock: Enhanced breeding, increased weight and milk production, and production of valuable substances by transgenic animals.

Cloning

Cloning is used to isolate and replicate genes of interest.

  1. Isolate the gene: Fragment DNA with restriction enzymes (which recognize specific DNA sequences and cut both strands of the double helix).
  2. Ligation: Bind DNA fragments to a cloning vector (a DNA molecule used to introduce a foreign gene into a host cell, e.g., a plasmid) using DNA ligase (an enzyme that joins sticky ends – single-stranded DNA sections with complementary bases).
  3. Transformation and Amplification: Introduce the recombinant DNA molecule into a host organism for replication (gene amplification).
  4. Detection: Detect the cloned gene and identify cells carrying it.