S.Nance: Gene Organization & Expression Flashcards
Chromosome
Chromosome – single circular, very little non-coding DNA
Exceptions for chromosome
two circular – vibrio, linear – Borrelia
Chromosome Function
Function – code for normal growth products
Plasmids
Plasmids – extrachromosomal DNA, covalently closed rings, some linear
Plasmid function
Function – non-essential for normal growth, antibiotic resistance and virulence genes, promote their own transfer (conjugative)
Horizontal gene transfer
Horizontal gene transfer – acquiring DNA from the environment and incorporating into bacterial genome (not from mother cell)
Pathogenicity islands
Pathogenicity islands – Type 3/4 secretion systems, MRSA, β lactam resistance
Genetic Replication of Chromosome
Chromosome – single origin (oriC) → DnaA recognizes oriC → bidirectional replication → forks meet on the opposite side
Genetic Replication of Plasmids
Plasmids – encode oriV → Rep to recognize oriV → replication, oriT → transfer to another cell
Gene Transcription: Operons
Operons – genes in the same metabolic pathways, induced or repressed when needed
Gene Transcription: RNA polymerase
RNA polymerase – single enzyme for transcription, reads until it reaches promoter sequence – terminator of hairpin repeats
Gene Transcription: Positive Control
Positive control – activate transcription, ex: cAMP inversely relates to glucose content
Gene Transcription: Negative Control
Negative control – block transcription, prevent RNA polymerase binding/leaving promoter region
Two component systems:
Two component systems: sensing environment signals
Sensor Kinase Component
Sensor kinase – auto-phosphorylates in response to signal → phosphorylates response regulator → regulates gene transcription, Ex: Salmonella in low Mg2+
