Second Half F24 II: Lecture Slides: 1 - 17 Flashcards
What did Chargaff’s founding in all cellular DNAs?
That the Number of Guanine = The number of Cytosine and that the Number of Adenine = the Number of Thymine
What is “Chargaff’s Rules”
A = T
C = G
What did Rosalind Franklin and Maurice Walkins do?
They used X-ray crystallography to identify the secondary structure of DNA.
What did Rosalind Frank obtain?
The first useful X-ray diffraction image of DNA: photo 51
What did Photo 51 show?
DNA molecules are helical
This photo provided information about the shape.
What is the primary/major pattern of the DNA?
3.4A
What is the minor pattern of DNA?
34A
What did Francis and Crick say the structure of DNA was?
Double Helical
What do the two helical DNA chains wind around a single axis form?
A right handed double helix.
Where does the hydrophilic sugar phosphate backbone remain?
On the outside of the helix facing the surrounding water.
What are the nitrogenous bases considered to be?
Hydrophobic
Where do the hydrophobic bases remain?
They are stacked inside the double helix perpendicular to the axis.
What are the two strands of DNA?
They are antiparallel to each other: the 3’.5’ phosphodiester bond run in opposite directions.
What is the distance between each base pair?
3.4A
What is the distance between 10 base pairs?
34 A
What is the diameter of the double helix?
20A (2nM)
What does self - complementarity allow each pre-existing strand of a double helix to serve?
As a template to guide synthesis of new daughter strands.
How many hydrogen bonds between Cytosine and Guanine?
Three
How many hydrogen bonds between Adenine and Thymine?
Two
What happens when you have a higher ratio of GC to AT
It will be more difficult to pull the strands apart as there are more hydrogen bonds.
What can DNA undergo?
It can undergo super-coiling to give very impact structures.
What are the glycosolic bonds between base pairs?
The glycosidic bonds are not collinear: they are at an angle.
What is the short angle of the glycosilic bond?
Minor Groove
What is the large angle of the glycosidic bond?
Major Groove
What forces stabilize the double helix?
1.) The hydrophobic effect (hydrophobic bases are within the core)
2.) The Hydrogen bonds
3.) Van Der Waals stacking of bases
What is the Central Dogma of Molecular Biology?
DNA —> RNA —> protein by transcription and translation.
