Lecture 11 Flashcards
if bacteria is a haploid can it have a dominant or recessive allele?
no it cant bc it has a single allele for everything
prototroph
wild type that is self sufficient
-e.coli strain will grow with minimal media that has sugars as a carbon source and salt
auxotroph
mutant that cant grow on minimal media unless it is supplemented with a specific compound
-just like the arginine experiment
what does replica platting allow you to do?
phenotype the bacteria
-grow the cells on a rich media so you can find the colonies and strains that dont have the genes to grow on minimal media
conjugation
bacterial sex
-pilli transfers information
-a non donor cell can inherit the ability to be a donor
-b would be receptor and then b+ would be the donor once it inherits the F+
donor gene
-F
-fertility factor
-lives on donor plasmid
-small circular DNA but NOT the chromosome
-plasmid does not always have F factor
-causes plasmid to extend pillis where a single strand will pass through to the recipient to be replicated into a second strand
Hfr strain
-an F+ strain that is better at donating all the genes EXCEPT the F+ gene
-The F+ gene of Hfr is on the main chromosome NOT the plasmid
why dont Hfr transfer F+ gene?
-because it is transfering the entire chromosome and the F is the last to get transferred
-before the F can get through the pillis breaks bc it is fragile
exogenote
linear DNA from the F gene not getting all the way through so it cant complete the circle
-it will recombine into the recipient chromosome bc bacteria do not like linear DNA
-the rest of the exogenote after recombination gets lost
endonote
circular DNA in the recipient
What do Hfr have?
fragile pillis
What can we use Hfr for?
to map bacteria chromosomes
-ex: crossing a drug resistant strain to a non drug resistant strain and blending the bacteria at different times to see at what time each gene transferes
-this will give us a map in minutes of where genes are on the chromosome
does every bacteria strains have the same gene order on chromosome?
no
-because the chromosome is not linear (this is the genetic evidence for circular chromosome)
what changes the order in which genes enter the recipient cell?
the location of the F on the chromosome and the F can be in a different location each time
recombination frequency mapping
a more specific map of where things are but it only works for exogenote that is transferred with an even number of recombination
Can Hfr reverse? and what does it create?
yes, this causes F to pop out of the chromosome and go back to the plasmid
-the risk is that is accidentaly takes other gene with it not just F
-this is what creates diploid
-ex: F takes lac w it to the recipient from the main chromosome. The recipient already has lac in its main chromosome so now it is a diploid for the lac gene which can be dom or rec.
proof that every adult cell encodes the entire genome?
remove the nucleus of the frog cell and replace it with intestinal cell and the frog egg still births a frog
What determines gene expression?
cis regulatory regions determines what gets turned off and on
What happens when e.coli detects the presence of lactose?
makes beta galactosidase to metabolize the lactore
-the enzyme will hydrolyze the beta glycoside linkage turning lactose into galactose and glucose
what happens to galactose?
it enters glycolysis
What enzyme allows lactose to enter E.coli?
lac protease
What happens if both glucose and lactose are present?
E.coli consumes glucose first then makes the enzymes to consume lactose
positive gene regulation
making enzyme to digest lactose
How can we measure beta gal activity?
use x gal (blue coloring) or yellow (quantitative bc the intensity of the color varies bc of the metabolization of ONPG)
-color means that the cell is producing enzyme
purpose of inducer?
to trick the e.coli into making enzyme
-looks like lactose but cant be used by e.coli
what encodes permease?
lac y
encodes b gal?
lac Z
ecoli structural genes?
lac a, z, y
-they are coregulated
will a lac z mutation affect lac a or y
no
lac I
-inducer
-mutation here makes the structural genes constitutive (always making enzyme)
-mutation increases enzyme activity
-away from the other structural genes
-ITTG
lac O
next to the other structural genes
-mutation can cause constitutive or no enzyme activity
-genes that never turn on are close to the far side of O y lose que siempre estan prendido estan next to structural genes
episome
donatable gene
mereploidy
partial diploid
What makes lac O cis?
turns on genes on the same chromosomes
-located on the same gene it regulates
trans
typically protein or RNA molecules that can regulate genes on the same or different chromosomes
What makes lac I trans?
it can regulate genes no matter where they are on the chromosome or plasmid
I^s
silent allele
-no enzyme produced
what type of allele is I
constitutive
Can Lac I be split into 2 regions like lac O?
no because lac I genes are all over the place
Which type of I is dom?
I^s is dom therefore it can block enzyme production from any location since it is spread out
Lac O regions
-P (tells cell to being making protein)
-O (traffic light that can switch gene on or off) (can stop enzyme production to save energy)
