Phage and Bacterial Genetics Lec 14 + 15
Genetics 466 with Chang/laughon/masson at University of Wisconsin - Madison
About this deck
By: Brian Ofori-Amanfo
Textbook:
Introduction to Genetic Analysis
Principles of Genetics
Created: 2010-03-14
Size: 24 flashcards
Views: 19
Textbook:
Introduction to Genetic Analysis Principles of GeneticsCreated: 2010-03-14
Size: 24 flashcards
Views: 19
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What is a Virus?
*obligate intracellular parasite capable of
autonomous replication in host cell.
Phage?
is an intracellular bacteria and can't survive outside a bacteria alone.
-it reproduces rapidly.
Bacterial cultures were lyzed when inoculated with fluids containing a virus.
**Bacteriophage = ?Bacteria eater?
**They discovered some bacteria will lyze. They realize that a virus causes the cell to lyze.
What are the 2 types of phages based on their life cycles?
*lytic and lysogenic
What is an example of the lytic phage?
T4 - the DNA that it injects is linear for the lytic phage whiles the DNA injected in the lysogenic phage is circular.
** in the Lytic phage, once the phage has pushed its DNA inside the bacteria, it hijacks the system and makes the DNA inside make RNA that will be used by the virus.
Sizes of the 2 phages:
lysogenic phage is smaller than lytic phage. Lysogenic phage is also called lambda.
Which of the phages have a complex life cycle?
Lysogenic, it is incorporated and almost silenced in the chromosome. It involves a lysogenic phage (a copy is integrated in the chromosome and remains silenced there. then later it will be lysed and expressed.
What are the ways to make a phage?
*Liquid culture-one bacteria lyses to form a lot of phage particles.
* Solid Medium-has nutrient.
What is the difference between a plaque and a colony?
**Plaque is cloning, start w/a single particle and make many.
**Colony is a large size group of organisms.
What are the 2 ways bacterial phenotypes can be determined.
Phenotypes: Lysis of bacteria
? Host range: A specific phage can only infect
specific strains of bacteria
? Plaque morphology: Large or small plaque,
function of speed of lysis
What affects B, B/2 and B/2 + B strain?
*Everything strain infects and forms plaque on the B strain. Everything is clear
*Only the mutant T2 can infect the mutant B strain (B/2). The mutant T2h is clear
** All can infect and form a plaque on the mixture, but the mutant will be turbid.
Plaque morphology
? Rapid lysis phenotype of T?even phages
? r+: small plaques with fuzzy edges
? r: large plaques with sharp edges
Phage Crossing
Can lead to offsprings that have the parent phenotypes at high freqs and recombinants at lower freqs.
How can you tell which ones are the recombinants?
The way to tell the recombinants is by inoculating B + B/2 cells because it will correspond to phenotypes.
what is recombination reciprocal?
Because we generate both h+r+ and h-r-. at the same freq. If only one shows up because the other is lethal, multiply by 2.
How do you get progeny phage?
? 1) Infect B cells with a mixture of T2h+r and
T2hr+ (cross) => Recover progeny phage =parental progeny
How do you get recombinant phage?
? 2) Inoculate progeny phage on B + B/2 cells = T2hr and T2h+r+
? Problem: If the progeny of a cross between hr+ and h+r is plated on B/2 cells, we cannot determine the total number of progeny!!!
? ==> Plate a fraction of the progeny on B cells
? ==> Total number of progeny
? ==> Plate the rest of the progeny on B/2 cells
? ==> Half of the recombinants will grow (h+ will not grow)
» RF = 2 x [hr]/[progeny plaques on B]
Fine mapping in phage
? rII mutants of T4 do not infect K12(?) (conditional lethality)
? rII mutants of T4 give large plaques on B
? r+ (wild type) of T4 gives small, fuzzy plaques on B and K12(?)
How can you get complementation?
If the 2 mutation genes (rll+ and rll-) affect 2 different cells, you will have complementation and plaque formation.
** No complementation , no plaque formation means the 2 genes affect the same gene in the r locus. The trick is to find a set of overlapping mutation.
**The mutations need to be recessive.
If a1 and b1 are recessive, this cell expresses both A and B functional products
Means a1 and b1 are on different genes and don't overlap, therefore they complement each other.
No Func>onal A product within the cell ==>
non produc>ve infec>on ==> No plaque
? Result 2: rIIa1 and rIIa2 are in the same gene and they overlap
i>clicker Questions
Feb 19 and 22 clicker questions
If rII9400 was dominant, we will have plaques.
About this deck
By: Brian Ofori-Amanfo
Textbook: Introduction to Genetic Analysis
Principles of Genetics
Created: 2010-03-14
Size: 24 flashcards
Views: 19
Textbook:
Introduction to Genetic Analysis Principles of GeneticsCreated: 2010-03-14
Size: 24 flashcards
Views: 19
About StudyBlue
STUDYBLUE makes things that make you better at school.
Things like online flashcards with photos and audio.
Things like personalized quizzes and friendly reminders about when (and what) to study next.
Think of it as a digital backpack™: access to all of your study materials online and on your phone.
STUDYBLUE exists to make studying efficient and effective for every student, for free. Join us.
“Simply amazing. The flash cards are smooth, there are many different types of studying tools, and there is a great search engine. I praise you on the awesomeness.”
Dennis
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