Lecture 8 - Bacterial Genetics

Bacterial Genetics: In-Depth Notes

Genetics: The science of heredity.
Gene: A segment of DNA that codes for functional products (proteins or RNA).
Heredity: The replication and transmission of genetic information.
Genome: The entire genetic material of an organism, can change due to replication errors, damage, or horizontal gene transfer.
Chromosomes: Organize the genome; prokaryotes typically have a single circular chromosome, while eukaryotes have multiple linear chromosomes.

Genotype: The genetic makeup of an organism, representing all alleles.
Phenotype: The observable physical properties of an organism, resulting from the expression of the genotype.

Wild Type Strain: The normal functioning organism, from which mutants arise.
Mutations: Alterations in DNA that can be passed to progeny and lead to a mutant strain.
Positive Selection: A method to isolate mutants that have a specific advantageous mutation (e.g., antibiotic resistance).
Negative Selection: Used when the desired property cannot be directly selected (e.g., inability to synthesize specific amino acids).

Spontaneous Mutations: Errors that occur naturally, often during DNA replication, more common in organisms lacking proofreading mechanisms (e.g., RNA viruses).
Chemical Mutagens: Substances that can cause changes in DNA structure, leading to base substitutions or frameshifts.
Base Substitution: A mutation where one base is replaced by another, causing missense (wrong amino acid), silent (no change), or nonsense (early stop codon) mutations.
Frameshift Mutation: Involves addition or deletion of bases, altering the reading frame and usually leading to truncated proteins.

Chemical Mutagens: Interfere with base pairing and can lead to misincorporation during DNA replication.
Nucleoside Analogs: Mimics of normal nucleotides that can lead to incorrect base pairing during replication.
Intercalating Agents: Chemicals that insert between base pairs, causing replication errors.
Radiation: Causes DNA damage, leading to mutations through mechanisms like thymine dimer formation or double-stranded breaks.

Excision Repair: A method for fixing UV damage where damaged DNA is removed and replaced with correctly synthesized DNA.
SOS System: A stress response that activates error-prone repair pathways when extensive DNA damage occurs.

Ames Test: A method to assess mutagenic potential by using mutant strains of bacteria to detect back mutations.

Mechanism: Involves nicking of DNA, strand invasion, and formation of Holliday junctions, aiding in genetic diversity through recombination.

Transformation: Uptake of foreign DNA by competent bacteria, which can integrate into their genome.
Conjugation: Direct transfer of plasmid DNA between bacteria via a pilus, often transferring genetic material that confers advantages such as antibiotic resistance.

Definitions: Extra-chromosomal DNA that can replicate independently and often carries genes for antibiotic resistance.
Types: Resistance plasmids and virulence plasmids, both contributing to microbial adaptability and pathogenicity.

Definition: Mobile genetic elements that can move within the genome, causing mutations. They can be simple (insertion sequences) or composite (carrying other genes).

Function: A bacterial immune system that uses segments of viral DNA (spacers) to recognize and cut invading viral DNA.
Stages: Adaptation (acquisition of spacers), expression (production of crRNA), and interference (cutting of the target DNA using the Cas9 enzyme).

Note

0.0(0)

Chat with Kai