Dna as genetic material?
Fredrick griffith -transformation experiment
Confirmation of genes made up Dna -hershy chase experiment
CHAPTER 2:
chemical nature:
Nucleoside-base+sugar
Nucleotide-base=sugar=phospahte
Dna structure:
B form : 10.5bp/helical turn,,34 A',
distance between 2 strands is 3.4 nm
A form: 11bp /helical turn,,31 A'
distance between 2 strands is 2.8 nm
Z form: 12bp /helical turn
distance between 2 strands is 4.5 nm
RNA-DNA hybrid(as same as A form)
Seperation of two strands of DNA double helix:
seperation promoted by temperature, dimethyl sulfoxide, formamide,high PH, low ionic strength, distruption of H2 bond.
Melting point observed by O.D (260 nm)
Hyperthermic shift
G+C content determines the melting point of DNA
G+C content determines density of DNA
Renaturation of seperated strands:
Renaturation determined by temperature (25'C),conc. of DNA , renaturation time.
Size and shape of DNA:
convert base into length : 10.5 bp /turn = 34A' (dist btwn 2 strands 3.4 A')
convert base into molecular weight : bp *660
( size of the DNA can be estimated by AGE)
For larger DNA molecule upto Mb by PFGE(Pulse Field Gel Electrophoresis)
