Genetics of Bacteria and Viruses 1 Flashcards
Most of the cells ont his planet are ___
Prokaryotes
Prokaryotes lack ___ and have __ __
Lack nuclei
Circular chromosomes
Prokaryotes are comprised of ___ and ___
Bacteria and Archaea
Bacteria have viruses called ___ or ___
Bacteriophages or phages
How do prokaryotes multiply?
Binary fission
How do bacteria carry their DNA?
A circular genome and circular plasmids
What carries genes that influence bacteria traits?
Plasmids
How many mechanisms for bacterial DNA transfer did we cover?
3
What are the 3 mechanisms for bacterial DNA exchange?
Transformation
Transduction
Conjugation
Transformation:
DNA is taken up from its environment
Transduction:
Receiving DNA from viruses
Conjugation:
receiving DNA from another cell
Conjugation can result in transfer of ___ or ___
Plasmids or genomic DNA
Vertical transmission:
Horizontal transmission:
Vertical - parents to offspring
Horizontal - between the same generation
Donor F+ only transfers to
Receipient F-
Hfr:
High frequency recombination
Hfr crosses to F- strains=
Virtually no F-
Parents are converted to F+ or Hfr
Normal F+ strains convert ___ ___ of F- parents into F+
Large fraction
What are Hfr strains a result of?
F plasmid being integrated into the chromosome
Double crossovers must occur in bacteria or __
the soul will be unviable
The F plasmid can integrate into ___ ___of the E.coli chromosome
Specific regions
What are the two outcomes of F- mediated conjugation?
F+ - independent circle of DNA
Hfr- plasmid has incorporated into chromosome
Does a single crossover result in a viable recombinant?
No, it does NOT restore circular DNA
F’ plasmids are a result of:
Popping out of chromosome and picking up genomic DNA with it
Naturally competent:
Can take up DNA from the environment
Free DNA being taken up is an ___ process
Active
ssDNA that has been taken up may ___ into the chromosome
integrate
Phage consists of:
A nucleic acid chromosome surrounded by a coat of protein molecules
Some phages have ___ chromosomes while others have ___ chromosomes
DNA
RNA
How do phages share DNA with a cell?
Phages bind to the surface of a sell and inject their DNA into that cell
A single phage can:
Hijack a cell and turn it into a factory for more phage
h and r genes
h influences:
r determines:
h -whether a phage can infect two different E. coli strains
r - whether the phage quickly or slowly trigers lysis
How many types of different phages are there?
What are they?
4
Virulent
Temperate
Prophage
Lysogen
Virulent:
They immediately lyse and kill the host
Temperate:
Can remain within a host for a period without killing it
Prophage:
A phage integrated into the hosts genome
Lysogen:
A bacterium harboring a prophage
Phage transduction:
Some phage can pick up bacterial DNA and transfer it to another cell
Generalized transduction:
Transducing phage can carry any part of the bacterial chromosome
Specialized transduction:
Transducing phage can only carry specific parts of the bacterial chromosome
λ phage:
A specialized transducing phage that inserts by a crossover at a specific site in the genome
If a cell WITHOUT (non hfr) λ prophage receives λ prophage:
If a cell WITH (hfr) λ prophage receives λ prophage:
It will die
It is immune
λ prophage can pops out of genome:
No genetic change in the host and the phage is complete
Rare λ prophage outlooping:
Incomplete phage genome that contains some bacterial DNA
Plasmids often carry transposable elements
Transposon:
A sequence that can be translocated even in the absence of complementary sequence in the host DNA
