Genetic Code and Properties

Genetic Code and Properties

• Genetic code are sequences of nucleotides or nitrogenous bases in messenger RNA (mRNA)
• mRNA sequences originate from DNA, their bases are complementary to DNA's segment.
• There are 20 different amino acids in the body, but only four nitrogenous bases (A, U, G, and C) in mRNA.
• 61 of the 64 triplet codons code for amino acids.
• UAA, UAG, and UGA are termination codons.
• AUG is the initiation codon, coding for methionine.

Properties of Genetic Code

• Triplet: Three nitrogenous bases form a genetic code in a specific sequence.
• Commaless: No punctuation marks between adjacent genetic codes.
• Non-overlapping: No codon overlaps with the next one.
• Universality: Same genetic code applies to all organisms, including viruses.
• Degeneracy: Multiple codons can code for the same amino acid.
• Ambiguity: A codon only codes for one specific amino acid.
• Collinearity: Linear arrangement of codons on mRNA corresponds to amino acid residues in the polypeptide chain.

Transcriptional Regulation

• A cell regulates the conversion of DNA to RNA (transcription).
• Bacterial transcription is controlled by three main elements:
  • Promoters: DNA segments where RNA polymerase and other proteins bind, initiating transcription. Located upstream of the gene.
  • Operators: DNA segments that bind repressor proteins to inhibit gene transcription.
• Positive control elements bind to DNA, increasing transcription rates.
• Operons are functional units of DNA containing genes under a single promoter, transcribed together into mRNA.

Genetic Engineering

• Genetic engineering, or genetic modification, manipulates an organism's genes using technology.
• It's used to change the genetic makeup, transfer genes between species, and produce improved organisms.
• It replaces or corrects defective genes for biomedical applications.
• It can introduce genetic changes to fix genetic disorders, create vaccines and other products, improving crop yields/nutrition, and resilience to environmental stresses.
• Researchers isolate gene candidates.
• Restriction enzymes cut DNA, or PCR amplifies the segment.
• The gene is inserted into a plasmid that’s inserted into bacteria for replication.

Recombinant DNA

• Recombinant DNA (rDNA) combines genetic material from different sources.
• DNA molecules can originate from any species.
• Molecular cloning replicates a DNA sequence without altering it, inserting it in a vector for propagation.
• Copies are generated for analysis/protein production by altering expression/function.
• Cloning uses DNA from species to be cloned, and a host species for replication.
• Recombinant DNA is vital in biotechnology, medicine, and research.

Transgenic & Knockout Animals

• Transgenic animals have altered or additional genetic material.
• Knockout animals have deleted or modified genes.
• Techniques like pronuclear microinjection introduce genetic material.
• Gene targeting applies to mice, and is in development for other organisms.

Reverse Transcription & cDNA

• Reverse transcription synthesizes DNA from RNA using RNA-dependent DNA polymerases (reverse transcriptases).
• cDNA is synthetic DNA transcribed from specific mRNA.
• It has only coding sequences, and is a tool for gene cloning, and studying gene expression.
• Widely used to express proteins in cells that don't naturally express them.

Restriction Enzymes

• Restriction enzymes cut DNA at specific sequences.
• They're used, in part, to create rDNA.
• They safeguard prokaryotes against invading viruses, cutting foreign DNA.

DNA Sequencing

• DNA sequencing determines the order of nucleotides in DNA.
• The sequence reveals genetic information, including genes, regulatory instructions, and disease-causing mutations.
• Sanger sequencing (chain termination) is a method to routinely sequence short DNA regions (up to about 900 base pairs).