LECTURE 17 Flashcards
Chargaff’s rule
1) the amount of different bases in DNA is consistent for any one species but different for different species
2) A=30.4%. C=19.6%
T=30.4%. G=19.6%
The backbone of a DNA is
Hydrophilic
The bases of a DNA are
Hydrophobic
How do two strands fit together ?
Purine + pyramiding
Which bonds are used to bond together bases?
Hydrogen bonds
In what direction are DNA strands running
Antiparallel
DNA is a ________ handed helix
Right
What were the three models that were considered for DNA structure
1) conservative
2) dispersive
3) semi-conservative (Watson and crick model)
Conservative DNA model
Two parental strands unchanged after serving as templates for the new strands
Dispersive DNA model
Parent strands are fragmented, making it easier to separate the strands. The new molecules consists of pieces of parental DNA and new DNA, assembled as a mosaic.
Semi-conservative (Watson and crick model)
Two parental strands separate and serve as templates for the new strands
How can one distinguish the parents DNA strand form the daughter strand?
- dsDNA has a specific density (determined by A,C,G,T)
- cuz N is present in DNA, isotopes 14N and 15N are used and are incorporated into DNA when used.
Between 14N and 15N which is light DNA and which is heavy DNA?
14N = light 15N = heavy
In what solution were the DNA mixed in and why
Solution of CsCl, so that the CsCl gradient causes dsDNA to move and come to rest at a position in this solution that matches its buoyant density
Explain the beautiful experiment
The cells are grown in 15N, then put into 14N to reproduce, each generation , cells are extracted to observe changes in DNA
