Uses/ Properties Of DNA Flashcards
What is melting DNA?
A double strand is separated into two single strands
Describe the change in absorbance when meting DNA- why is this, what is the use of this?
Absorbance increases when double stranded DNA is separated (melted)
Purine and pyrimidine bases absorb UV light strongly
Double stranded DNA absorbs less strongly due to stacking interactions between the bases
Means you can follow process of melting by using UV vis- see when absorbance increases and decreases
How do you ‘melt’ DNA
Raise the temperature
Is single stranded or double stranded DNA more stable at higher temperature?
DNA is stable as double helix at higher temperature due to hydrogen bonds
What is Tm?
This is when 50% of DNA is double stranded and 50% is single stranded
How do you make DNA more stable at higher temperatures
Make it more GC rich as these bases have 3 hydrogens bonds rather than 2 and so there are more hydrogen bonds and it’s more stable
What is denatured DNA?
Single stranded DNA
Is melting and annealing reversible?
Yes
Describe the diagnostic use of DNA
Synthetically make DNA sequence- probe- make it complementary to pathogen DNA
Radioactively label it
Go fishing for complementary sequence of pathogen DNA
If you find complementary DNA (prove anneals)- person has infection
Describe the nature of bacterial DNA
Bacteria has circular molecules of DNA
What is topological isomerism
Relaxed and supercoiled are the forms of this isomerism
How is the topological state of DNA changed?
Enzymes interconvert DNA between relaxed and super coiled
Describe the difference between relaxed and supercoiled DNA in electrophoresis
Relaxed occupies more space and takes longer to go through matrix
Supercoiled is more compact and goes through gel faster
