DNA Flashcards
What do restriction endonucleases do? And what do they produce?
Cuts DNA sequance in a specific place
Produces stickey ends
In gel electrophesis, why do the DNA fragments travel towards the positive electrode?
As the phosphate in DNA is negatively charged
Explain how gel electrophesis works?
DNA samples are treated with restriction endonucleases to cut them up
These samples are added to the wells
An ionic buffer is added to the agrose gel, so that an electric current can be carried
Once turned on, the DNA moves towards the +ve electrode
Shorter DNA fragments travel further towards the +ve electrode
Explain how PCR occurs
The DNA strand is heated to 95 degrees (to break H-bonds)
The primer anneals to the single stands, and it is cooled to 55 degrees
The free nucleotides then complementory base pair with Taq Polymerase
Then it is heated to 72 degrees to form new DNA strands
Why is Taq Polymerase used in the PCR?
To form phosphodiester bonds
As normal DNA polymerase would become denatured in the hot tempretures
What are the differences between PCR, and sequancing using the PCR?
Terminator bases are added (that are fluorescent)
Gel electrophesis occurs, and UV light is used to visulaise terminator bases
What is a DNA probe?
A short single stranded piece of DNA that fluoreses under UV light, and is complementory to a specific section of DNA
How is recombinant DNA from a plasmid made?
A gene is cut out of some DNA with a restriction endonuclease
The same restriction endonuclease is used to cut a gap in a plasmid
The sticky ends complementory base pair, and DNA ligase is used to complete the sugar phosphate backbone
How can you find the DNA sequance of a protein when you only have a single protein?
X-ray crystallography to find the amino acid sequance
The DNA sequance can then be found
What is meant by the term ‘The shotgun approach’?
A chromosome is cut down into smaller fragments
These are sequanced indiviudually
Put back into the original order by a computer
How do we use BAC (Bacterial artificial chromosomes) to store genetic code?
Genetic code inserted into bacteria
Bacteria is replicated to duplicate the genetic code
Bacteria are frozen
The genetic code can then be removed when it is needed
1.5% of the human genome actually codes directly for polypeptides. What is that 1.5% called?
Eukromatin
Describe Somatic gene therapy
The gene is modified in a humans cell, but not in the reproductive cells
Can cure a disease, but this immunity is not passed down
Describe Germline gene therapy
The gene is modified when they are single celled (sperm/egg)
Can cure a disease, and the immunity is passed down
Define Xeno- and Allotransplantation
Xeno- = transplantation of tissues and organs between different species Allo- = Between the same species
