DNA Denaturation Flashcards
What else can facilitate denaturation? Why?
Lowering the concentration of salt in solutions of DNA …
The DNA is less stable when the ions are removed that shield the negative charges on the DNA strands from each other
How does DNA denaturation occur?
By heating, the presence of organic solvents (such as DMSO or formaldehyde), or by high pH…
This disrupts the hydrogen bonds between the DNA strands
Why can DNA denature at relatively low temperatures as well?
The repulsive forces of the negative charges
What is another term for DNA denaturation?
DNA melting
When does DNA denaturation occur?
When the DNA strands come apart
Define melting temperature
The temperature at which the DNA strands are half denatured
How is the degree of strand separation measured?
By the absorbency of the DNA solution at 260nm
Why do nucleic acids absorb light at 260nm?
Due to the structural properties of their bases
What does it mean if DNA ‘quenches’ some absorbance?
The two strands of DNA have came close together so the proximity of the bases to each other is reduced
(Ask Ryals)
Is the absorbance of dsDNA higher or lower than two ssDNA? Why?
Lower
If you increase the distance, you increase the absorbance and vice-versa
Describe the hyperchromic shift
When two strands separate, the quenching is reduced/removed and the amount of light absorbed at 260nm increases 30% -> 40%
What effect does GC content of DNA have?
Effects DNA stability, melting temperature, density
What happens with increases GC content?
Melting temperature and density increase linearly
Why does GC content affect melting temperature?
There is a third hydrogen bond in GC base pairs
What is thematically occurring amount of GC?
22% - 73%
