And the molecule of heredity is...

Question 1

Girffith’s experiment

Answer 1

• Two types of pneumonia bacteria strains
• streptococcus pneumoniae
• Virulent S-Strain = had polysaccharide “smooth” coating - protected it from immune system = more dangerous
• A-Virulent R-Strain = no coating= less deadly
• sometimes the R-Strain would transform into the S-Strain
  -must be a transforming principle

injected 5 types of bacteria into mice
- R-Strain only = survived
- S-Strain only = contracted pneumonia, died
- Heat killed S-strain = survived, as bacteria had died
- *Combo of heat killed S-strain and Live R-strain = developed pneumonia and died

• concluded the live R-Strain acquired component (transformation principle) from dead S-strain to make it deadly
• he isolated bacteria from Group 4 mice and it was identical to the live S-Strain

-proved that some organisms can acquire new properties from their environment and each other
- non heritable exchange of genetic info is possible

Question 2

Avery-Macleod-Mccarty Experiment

Answer 2

• initially didn’t know if DNA or Protein was the heredity molecule (most believed it was protein due to complexity)
• based on Griffith’s experiment
• PLERIMINARY TESTING tested on transforming materials:
  > soluble in salt solutions
  > stored at low temps for long periods
  > disable below pH 5
  > UV Maxima 2600 minima 2350 = MATCHES DNA
  >N:P ratio avg 1.67 = MATCHES DNA, eliminates carbs and lipids
  > precipitates out of solution = eliminates carbs

FURTHER TESTS TO CONCLUDE: (carbs and lipids removed via process of elimination)
- samples of heat killed s-strain + live R-strain
- injected into mice
> CONTROL - no component destroyed - transformation took place - died
> PROTEIN - proteases added to kill proteins - transormation took place - died
>RNA - RNAses added to destroy RNA - transformation took place - died
> DNA - DNAses (specifically DEPOLYMERASE) added to destroy DNA - transformation not took place - survived

Question 3

What is bacteriophage

Answer 3

• virus that infects bacteria
• protein protective coat surrounding nucleic acid core
• nucleic acid hijacks host
• uses its metabolism to replicate
• death of host cell

Question 4

Hershey and Chase Experiment

Answer 4

• T2 bacteriophage
• reproduce vry quick, and only made up of protein and nucleic acids
• in protein group, they made the protein shell radioactive via Sulfur 35 (not found in nucleic acids)
• in nucleic acids group they made the nucleic acid on the inside radioactive via Phosphorus 32 (not found in proteins)

INFECTION
- allowed it to infect host cell
- to see if protein or NAs would make radioative bacteriophages

BLENDING
- blended to shake the e coli enough to shake off empty protein coats on the outside
- created mixture liquid, phage parts and bacteria i.e. suspension

CENTRIFUGATION
- heavier bacteria condensed at the bottom
- virus shells stayed at top (supernatant)

progeny phages had 30% P32 label and ,1% of S35 label
therefore the DNA had entered the bacteria not the protein

Question 5

in hershey chase, why only 30% of DNA transferred to progeny phage?

Answer 5

semi conservatice replication
theoretically 50%, 30% experimental error
(theoretically the next generation would contain 15%)

Question 6

What is used to identify DNA using radioactive labels>

Answer 6

Phosphorus 32
14C not specific enough

Question 7

What is used to identify DNA using radioactive labels>

Answer 7

Phosphorus 32
14C not specific enough