Genetics: Horizontal Gene Transfer and Mutations

Horizontal Gene Transfer

• Horizontal gene transfer (HGT) is the transfer of genetic material between different organisms, not inherited from parent to offspring.
• Organisms that undergo HGT primarily include bacteria and some eukaryotes.
• Benefits of HGT include increased genetic diversity and the ability to gain advantageous traits like antibiotic resistance.
• Risks of HGT include spreading harmful traits, such as pathogenicity, and potentially disrupting local ecosystems by introducing foreign genes.

Mutations

• A mutation is a change in the DNA sequence.
• Mutations can be spontaneous or caused by environmental factors.
• Types of mutations:
  • Point mutations involve a single nucleotide change, such as missense, nonsense, and silent mutations.
    • Missense mutations change one amino acid,
    • Nonsense mutations create a premature stop codon,
    • Silent mutations do not change the amino acid.
  • Insertions/deletions (indels) involve adding or removing bases, potentially causing frameshifts.
  • Chromosomal mutations are large-scale changes, like duplications, inversions, or translocations.
• Mutations can have various impacts, ranging from benign to beneficial or harmful. Some mutations lead to genetic disorders, while others can offer an evolutionary advantage.
• Examples include beneficial mutations, like resistance to disease, and detrimental mutations, like cystic fibrosis, where a mutation in a single gene leads to thick mucus in the lungs and digestive tract.

DNA Replication and Repair

• DNA proofreading is a process where DNA polymerases check and correct errors during DNA replication.
• Mismatch repair detects and corrects errors in DNA replication after the process is complete.
• These systems are important for maintaining the stability of the genome.

Chromosome Structure and Organization

• Bacteria typically have a circular, single chromosome.
• Bacterial DNA lacks histones and forms a nucleoid region.
• Eukaryotes have linear chromosomes within a nucleus.
• Eukaryotic DNA is wrapped around histones, forming chromatin.

Transcription and Translation

• Transcription is the process of copying DNA into mRNA.
• Translation converts mRNA into proteins.
• Gene expression describes how genes influence traits through the production of proteins.

Gene Regulation

• Repressors are proteins that bind to DNA and inhibit transcription.
• Activators are proteins that bind to DNA and improve transcription.
• In bacteria, repressors and activators directly interact with operons.

PCR and Gel Electrophoresis

• PCR (Polymerase Chain Reaction) amplifies specific DNA sequences.
• Gel electrophoresis separates DNA fragments by size, allowing visualization of PCR products or genetic differences.

Central Dogma and Gene Regulation

• Gene expression is regulated at various stages of the Central Dogma, controlling transcription, translation, and post-translational events.
• This regulation allows cells to precisely respond to environmental signals and control protein production as needed.

Non-coding RNA

• Non-coding RNAs (ncRNAs) are RNA molecules that don't code for proteins but play various roles in gene expression and regulation.
• Examples of ncRNAs include ribosomal RNA (rRNA), transfer RNA (tRNA), microRNAs (miRNAs), and small interfering RNAs (siRNAs).

DNA Sequencing

• DNA sequencing is the process of determining the precise order of nucleotides in a DNA molecule.
• It's a critical technological advancement for understanding genetic makeup, diagnosing genetic disorders, and conducting evolutionary studies.