Study Prep: Microbial Genetics Summary

GRIFFITH EXPERIMENT

• Demonstrated that an unknown genetic "factor" controls traits of organisms (1928).

• Introduced concept of Transformation: incorporation of external DNA causing genotypic/phenotypic change.

HERSHEY-CHASE EXPERIMENT

• Confirmed DNA is genetic material using bacteriophages (1952).

• Showed only viral DNA, not protein, enters bacteria during infection.

CHARGAFF'S RULES

• Base composition varies between species.

• A=T and G=C within each species, leading to base pairing rules.

STRUCTURE OF DNA

• Rosalind Franklin's work led to the discovery of DNA as a double helix by Watson & Crick (1953).

• Complementary base pairs: A–T and C–G bonded by hydrogen bonds.

MESELSON-STAHL EXPERIMENT

• DNA replication is semi-conservative: each new molecule has one parental and one new strand (1958).

DNA REPLICATION

• Initiated at origins of replication (ORI).

• Involves key enzymes: helicase, DNA polymerase, primase, and ligase.

• Leading strand synthesized continuously; lagging strand in segments (Okazaki fragments).

CENTRAL DOGMA

• Flow of genetic information: DNA → RNA → Proteins (transcription and translation).

• Transcription produces mRNA from DNA template.

EUKARYOTIC RNA PROCESSING

• Involves capping, polyadenylation, and splicing to produce mature mRNA.

• Introns are removed, exons joined together.

TEPS OF TRANSLATION

• Initiation, elongation, and termination sequence process.

• Ribosomes facilitate translation of mRNA into proteins using tRNA.

MUTATIONS

• Permanent changes in DNA sequence; can be spontaneous or induced by mutagens.

• Types include point mutations, insertions, deletions, and frameshift mutations.

HORIZONTAL GENE TRANSFER

• Mechanisms include transformation, transduction, and conjugation.

• Enables genetic diversity among bacteria.

CRISPR-CAS SYSTEM

• Bacterial immune system against phage infections; involves storing viral DNA fragments and targeting them during reinfection for destruction.