Microbial Genetics Flashcards
What is the bacterial genome typically?
Singular circular chromosome
Where is the chromosome found in bacteria?
There is no nuclear membrane so it is restricted to a defined region of the bacterial cell known as the nucleoid
What are plasmids?
Other small circular self replicating DNA molecules that are found in the cytosol (separate to the main chromosome)
What is the engine behind horizontal and vertical gene transfer?
Mutation
What is horizontal gene transfer?
Directly from one organism to another
What is vertical gene transfer?
From parent to offspring
What does streptococcus pneumonia cause?
Pneumococcal disease
What is the strains of pneumococcal disease?
Smooth (has a capsule) and rough (no capsule)
What is the deadly strain of pneumococcal disease and why?
Smooth strain because the capsule prevents phagocytosis and being recognised by the immune system
What happened when live smooth cells were injected into the mouse?
The mouse died
What happened when heat treated (dead) smooth cells were injected into the mouse?
The mouse survived
What happened when live rough cells were injected into the mouse?
The mouse survived
What was involved in Griffith’s experiment?
Live rough cells and heat treated (dead) smooth cells injected into the mouse
What were the results of Griffiths experiment?
The mouse died and live smooth cells could be grown on a culture indication that rough cells had been transformed to smooth
What are the types of horizontal gene transfer?
Transformation, conjugation and transduction
What is involved in transformation?
Involves the uptake of short fragments of naked DNA by naturally transformable bacteria
What is involved in conjugation?
Transfer of DNA material via sexual pilus and requires cell to cell contact
How is the DNA transferred in conjugation?
The circular plasmid unwinds and feeds through the pilus
What is involved in transduction?
Transfer of DNA from one bacterium into another via bacteriophages
How does transduction occur?
The phage virus binds to the bacteria and injects its DNA so the virus reproduces all of its components. When piecing back together sometimes mistakes are made and bacterial plasmid is included which can then be injected into other bacteria
How can exchange of genes occur?
Can be lytic as in transduction or also lysogenic where viral DNA is incorporated into normal DNA to form a phage
