Introductory Lecture Flashcards
1
Q
What is the Griffith Transformation experiment?
A
- 1928
- Involved pneumonia causing bacteria (Pneumococcus)
- 2 strains - smooth and rough
- Smooth bacteria that was heated up didnt kill mice
- Heat-killed smooth bacteria and live rough bacteria killed mice
- BUT live smooth bacteria was recovered from the dead mice
2
Q
What is the Avery-McCarty-Macleod experiment?
A
- Made extract from heat killed smooth bacteria
- Mixed extract with live rough bacteria and different ezymes, injected them respectively into rats
- Extract only - die
- Protease-treated extract - die
- RNase-treated extract - die
- DNase-treated extract - LIVE
3
Q
In regards to the Griffith and AVery-McCarty-Macleod experiments…
What is the conclusion of these experiments?
A
- Mice infected with:
- smooth S strain of Pneumococcus - die
- rough R strain of Pneumococcus - live
- live R and dead S - die
- Live S bacteria are recovered from dead mice
- Transforming principle is able to convert R bacteria to S
4
Q
What is a bacteriophage?
A
- A virus - one of the simplest organisms
- A protein coat surrounding a nucleic acid core
- Nucleic acid hijacks the host and reprogrammes the cell
- Genetic material is injected into host
- Often results in death of the host cell
4
Q
What is the transformation principle?
A
- Digest w/ DNase, RNase or protease
- Make extracts of killed S strain bacteria
- Only extracts treated with DNase do not transform
- DNA is able to transform R bacteria to S
4
Q
What is the Hershey and Chase experiment?
A
- 1952
- The genetic material of phage T2 is DNA
- Infect bacteria with phage labelled with radioactive isotopes
- 32P in DNA and 35S in protein
- Separate phage coats and infected bacteria
- Phage - mostly 35S label went in
- Infected bacteria - mostly 32P label went in
- Isolate progeny phage
- Progeny phages contain 30% of 32P label and <1% of 35S label
- DNA, not the protein, enters the bacteria
- DNA is passed down
5
Q
Why is only 30% of DNA transmitted to progeny ‘phage’? Ideally what should the percentage be?
A
- semi-conservative DNA replication
- ~9%
6
Q
In an experiment to track the fate of DNA in a replicating micro-organism, labelled nucleic acids could best be distinguished from other cell constituents if it was labelled with:
A
32P (phosphorous)
