1-10 Bacterial Genetics Flashcards
Common features between prokaryotic and eukaryotic gene expression
Both involve promoter sequences, binding of rna poly, a site marked by ATG, an open reading frame, a stop codon
Major differences between prokaryotic and eukaryotic gene expression
eukaryotes organize genetic material into genes. Prokaryotes uses operons.
Eukaryotes rely on various transcription factors. Prokaryotes have operators, activators, and repressor molecules (often metabolic deficiencies or excesses)
eukaryotes have enhancer sequences and perform RNA splicing. Prokaryotes have neither
Cite the three major processes by which bacteria transmit and acquire new genes.
Transformation, conjugation, transduction
Transformation
Transformation - bacteria pick up free floating DNA fragments (often from lysed cells) sometimes with recombination of DNA into the bacterial genome via homologous recombination.
RARE - due to restriction/modification system. DNA must get through restriction enzymes which methylate the bacterias own DNA in a specific pattern, repair damaged DNA, and splice in DNA that is modified (methylated).
Conjugation
DNA transferred directly from one bacteria to another. F-PLasmid is necessary.
F plasma can be incorporated into bacterial chromosome and then excised into plasma again when used for mating. When F plasma is excised, sometimes it takes and transmits neighboring genes other than just ones for making sex pilus.
Transduction
viruses transmit DNA into bacteria.
Generalized - phage causes lysis and release of bacteria’s DNA. May accidentally take some in prophage capsid to infect next cell.
Specialized - phage inserts into chromosome, aquires some regional DNA which then are carried to the next bacteria to be infected.
Explain how horizontal gene transfer affects the ability of bacteria to cause disease and resist treatment.
Horizontal gene transfer adds a great deal to bacterial biodiversity. If one bacterium obtains a beneficial chance mutation, that mutation can potentially be passed on to many other bacteria. Genes for new and improved toxins, antibiotic resistance, and other factors can be passed along between surrounding bacteria.
Describe the F-Plasmid
can exist as an extra-chromosomal element or can be integrated into the chromosome.
Bacteria can be F+ = males, F- = females, or Hfr = male with integrated plasmid due to high frequency recombination.
in Hfr, when it is replicated, parts of the DNA outside of the F is also copied and transferred to F- recipient and subjected to recombinatio
What are R-Factors?
segments of non-chromosomal DNA that carry genes for antibiotic resistance, some of which are small plasmids and some are large F factors
How do transposons and integrons effect the ability of bacteria to_______. How?
cause disease, resist ABX
transpons and integrons are elements which genes are arranged within that can move around the genome
- often includes a gene for an enzyme that allows transposition and possibly a drug resistance gene.
- transpon with this gene may relocate to an area where the F-Plasmid or bacteriaphage has integrated - allowing teh transpon to travel to another bacteria later on.
What is a compound transposon?
created when a transposon integrates into another transposon. this may code resistance to multiple antibiotics. A bacteria which received a compound transposon within an F-Plasmid or phage could thereby become resistant to multiple abx in one gene step
pathogenicity island
regions of bacterial chromsome where several adjacent genes contribute to the pathogenesis of a disease. Can transfer between bacteria via transformation, transduction, or conjugation
What encodes the ability for the F-Plasmid to transfer into a bacteria that lacks it?
The f-plasmid encodes this ability itself.
F-Factor vs a lytic phage?
F-factor requires donor and receipient to be alive. F factor is simply DNA, phage is complex particle
if a portion of bacterial chromosome was deleted, that bacteria may become more or less senstive to an antibotic depending on the nature of the antibiotic and nature of deletion. Why or why not?
True - if deletion encodes drug digesting enzyme, left more sensitive to abx.
if deleted region encoded an antibiotic receptor (target of the abx) it’s loss would leave the bacteria less sensitive.
