Mutations Flashcards
What senses nutrient deprivation for endospore formation
what initiates endospore formation
Sensor Kinase A
kinase cascade
activates sigma factors
Activation of sigma factors in endospores….
sigma F early sporulation
sigma G late sporulation
Endospore formation has two things. They are
spatial recognition (dif. sigma factors recognize different parts)
timing (activation of these sigma factors is dependent on kinase pathway)
endospore formation is due to
changes in gene expression
silent mutation
single base substitution that doesn’t cause a change in expression (usually third)
missesne mutation
single base substitution that causes expression of different AA
nonsense mutation
point mutation in a sequence of DNA that results in a premature stop codon
frameshift mutation
insertion/deletion of a number of nucleotides
forward mutation is followed by a
reversion follows
reversion mutations are utilized for
Ames test
Ames test
test for carcinogens
checking to see if carcinogenic because it causes increase in reversion (something that is already mutated)
genetic variation is caused by which 2 mechanisms
mutation
horizontal gene transfer
these can also lead to antibiotic resistance
3 mechanisms of horizontal gene transfer
conjugation
transformation
transduction
3 types of conjugation
F+ x F-
Hfr
F’
Hfr conjugation
F factor is integrated to chromosome
recombinant cells are found in a high frequency
F+ cell integrates into genome which then transfer genes from genome
recipient cells during Hfr, do they become F+?
NO
they are incapable of horizontal gene transfer
results of Hfr
2 F factor
piece of genome from donor cell that can undergo recombination
requires new phenotype but can’t horizontally donate to new cell
integrated into genome – what type of conjugation
Hfr
F’
F factor is excised out
transfer of F factor results in transfer of other genes that have been excised
which conjugation can only transfer what is excised out (F’ no longer associated with genome)
F’
No longer integrated in genome
F+ x F-
transfer of genes from F+ to F-
will have add-on basically of F plasmid
lytic phages do which type of transduction?
generalized transduction
what are the 2 types of transduction?
generalized and specialized
generalized transduction
phage breaks up during infection portion,
error in patching results in phage with part of e.coli cell genome
transferred to recipient cell
incorporated into genome
generalized transduction (general characteristics)
don’t generate more phages
2 phage system (one infects, one picks up some from donor cell DNA)
specialized transduction
carried out by temperate phages
must have lysogeny
steps in specialized transduction
lysogenized phage that has prophage
stimulated to turn on
rarely, but possible, but it pulls out some of host genes
when packaged it is carried on and infects immune cells
