Module 4
Flow of Genetic Material
Chapter 16-18
, Chapter 16
16.1 DNA IS THE GENETIC MATERIAL
• TH Morgan showed two chemical components of chromosome - DNA + protein
• Unclear whether the protein of DNA component is on the chromosome
• Derived experimentally!!
• Bacterial Transformation experiment
• Streptococcus pneumonia — used a rough (harmless) and smooth (pathogenic) strain
Gri th’s Experiment
• Why did the mice in experiment 3 die??
• Genetic exchange has occurred!
• DNA encoding for the capsule surrounding the smooths train is absorbed by the rough
strain which become pseudo-smooth strain and therefore function as the virulent S-strain
• TRANSFORMATION = a change in genotype and phenotype due to assimilation of
external DNA by a cell
• Radioactive Tracing Experiment
• Tested whether DNA or protein component of T2 phages infected bacterial cells to
reprogram them and produce more phages
• Radioactive sulphur + phosphorus sued to trace protein and DNA in E. Coli gut infection
• To infect a cell, virus must take over a cell’s metabolic machinery
ffi
, Hershey-Chase Experiment
RESULTS = when investigating proteins, they were found to exist outside of the bacteria cell but
when DNA was labelled, radioactivity was found inside the cell. Therefore, DNA can be regarded
as the genetic material of the T2 phage
NUCLEOTIDES
• =Monomer of DNA
• Nitrogenous base (A,G,C,T)
• Pentose sugar
• Phosphate group
• Charga ’s rules=
1. Base composition of DNA varies amongst species
2. Percentages of A+T bases and G+C bases are roughly equal (result of base pairing)
• Diversity across species increases credibility of DNA as genetic material
ff
Flow of Genetic Material
Chapter 16-18
, Chapter 16
16.1 DNA IS THE GENETIC MATERIAL
• TH Morgan showed two chemical components of chromosome - DNA + protein
• Unclear whether the protein of DNA component is on the chromosome
• Derived experimentally!!
• Bacterial Transformation experiment
• Streptococcus pneumonia — used a rough (harmless) and smooth (pathogenic) strain
Gri th’s Experiment
• Why did the mice in experiment 3 die??
• Genetic exchange has occurred!
• DNA encoding for the capsule surrounding the smooths train is absorbed by the rough
strain which become pseudo-smooth strain and therefore function as the virulent S-strain
• TRANSFORMATION = a change in genotype and phenotype due to assimilation of
external DNA by a cell
• Radioactive Tracing Experiment
• Tested whether DNA or protein component of T2 phages infected bacterial cells to
reprogram them and produce more phages
• Radioactive sulphur + phosphorus sued to trace protein and DNA in E. Coli gut infection
• To infect a cell, virus must take over a cell’s metabolic machinery
ffi
, Hershey-Chase Experiment
RESULTS = when investigating proteins, they were found to exist outside of the bacteria cell but
when DNA was labelled, radioactivity was found inside the cell. Therefore, DNA can be regarded
as the genetic material of the T2 phage
NUCLEOTIDES
• =Monomer of DNA
• Nitrogenous base (A,G,C,T)
• Pentose sugar
• Phosphate group
• Charga ’s rules=
1. Base composition of DNA varies amongst species
2. Percentages of A+T bases and G+C bases are roughly equal (result of base pairing)
• Diversity across species increases credibility of DNA as genetic material
ff
