1. Griffith's transformation of Streptococcus pneumoniae

Wild type = dead mouse

Heat-treated wild-type = alive mouse

Mutant (rough) = alive mouse

Mutant + heat-treated = dead mouse*

2. Avery et al further transformation experiments

Lyse and fractionate wild-type cells --> Separate carbohydrates:

Rough + Proteases = dead mouse

Rough + Nucleases = alive mouse

3. Hershey Chase blender experiment

³⁵S in Met and Cys of protein coat of bacteriophage --> Blend and centrifuge   --> Radioactive phage ghosts detected

³⁴P in DNA of bacteriophage --> Blend and centrifuge --> Radioactive infected cells detected

1. Storing genetic information

Sequence of bases encodes genetic info-any sequence allowed = good store

Double helix = 2 copies-for accurate replication + repair mechanisms

2. Allowing replication of genetic information

Double helix unwinds, complementary base pairing = template for new bases

Meselson-Stahl experiment:

E. coli grown in ¹⁵N (DNA = heavy-heavy) -->Transferred to ¹⁴N --> Samples taken over  generations --> DNA spun in CsCl gradient to separate by density:

After 2 generations, 50% = hybrid (H-L) and 50% = new (L-L)

Replication uses 1 original strand and creates 1 new strand = semi-conservative