Lecture 11 and 12 Flashcards
What bacteria causes respiratory disease and meningitis in infants and was the first complete genome to have its DNA sequenced?
Haemophilus influenzae
How many genes were identified in Haemophilus influenzae?
1743 genes
What software can be used to search for similar sequences to see what a gene does?
BLAST (basic local alignment search tool)
How can the function of a gene be determined?
- Mutants with defective genes
Identify effects of mutations (e.g. what metabolites are missing etc.)
Purify proteins and test in vitro functions
How many bacteria have had their whole genome sequenced?
More than 3000
What is the size range of a bacterial chromosome?
112kb to 14,800kb
What species has two circular chromosomes?
Vibrio species (cholera)
Name two bacteria with linear chromosomes
Borrelia burgdoferi (lyme disease) Steptomyces (antibiotic producers)
How many genes are there per kb?
1 gene per 1kb
What is a sequence of DNA coding for a sequence of amino acids long enough to be a protein?
Open reading frame
What bacteria has the smallest genome?
Nasuia deltocephalinicola
How big is N.deltocephalinicola ‘s genome?
112kb (141 genes)
Where is N.deltocephalinicola?
Obligate symbiont of a leafhopper
What is the confirmed species with the smallest genome?
Mycoplasma genitalium
What species have the largest genome?
Sorangium cellulosum (soil organims) Spretomyces species
What does Haemophilus influenzae cause?
Respiratory tract infections
What does staphylococcus aureus do?
Cause skin infections
Typical range of bacterial genomes
1800-6600kb (Up to 14,800kb)
Typical plasmid size
1-1000kb
Plasmid shape?
Covalently closed circle, supercoiled
How can rare mutations be identified using negative selection?
Replica plating
What type of bacteria is used in the ames test?
his- strain of salmonella typhimurium
What are the three mechanisms for horizontal gene transfer in prokaryotes?
Transformation, conjugation, transduction
Who first observed DNA transformation?
F Griffith
Who demonstarted the transforming principle is DNA?
Avery and McCarty
How does transformation occur?
DNA binds to DNA binding protein on membrane, one strand passes in, aligns with region of homology, homologous recombination occurs
What is conjugation?
Transfer of genetic material between bacteria through direct cell-to-cell contact
What is the fertility (F) plasmid?
Found in -ve bacteria
Circular DNA molecule
Contain DNA replication regulation gene
Contains tra genes that encode transfer functions (incl. sex pili synthesis)
What name is given to the binding of proteins in outer membrane during conjugation?
Mating bridge
Cells containing the integrated F plasmid are called?
Hfr (high frequency of recombination)
What is transduction?
Bacteriophage transfers DNA from one cell to another
What are the two methods of transduction?
Generalized transduction
Specialized transduction
What is generalised transduction?
DNA from bacterial chromosome packed into virion instead of viral genome
What is the resulting virion during generalised transduction called?
Transducing particle
What is specialised transduction?
Involves intergration of phage genome into host DNA (lysogeny), adjacent chromosomal gene hitchhikes with phage DNA into virion
