Gel electrophoresis

Question 1

State the name of the technique for separating out DNA fragments

Answer 1

Gel electrophoresis

Question 2

Describe how to carry out this technique

Answer 2

(before gel electrophoresis)
-create DNA fragments using restriction endonuclease enzyme
(cuts out short tandem repeats)
-amplify DNA via polymerase chain reaction
-separate the fragments by gel electrophoresis: DNA with restriction endonuclease enzymes mixed with loading dye (to visualisation)
-add buffer solution to agarose gel in electrophoresis tank (to transmit charge through tank and stabilisie pH)
-restriction ladder added to one well in electrophoresis tank as a reference
-add current to tank
-DNA fragments will be attracted to anode due to slight - charge and different length fragments will end up closer to anode if theyre shorter
-visualisation of the different lengths of fragments will be produced
-UV light can be used to visualise fragments
-CVs=need enough sample so PCR must be done correctly
?
sample with DNA added

Question 3

Explain why DNA moves to the positive electrode in gel electrophoresis ​

Answer 3

Phosphate groups in DNA nucleotides give it a slight - charge

Question 4

Explain how the size of the DNA fragment determines the distance it moves in the gel

Answer 4

Longer fragments cant move as quickly through the gel so smaller fragments will end up closer to the anode

Question 5

An antelope is found dead in Kruger National Park. The park rangers suspect that the antelope was killed by a cheetah, they take a sample of saliva from the wounds in the antelope. Explain how the park rangers could use gel electrophoresis to identify whether the antelope was killed by a cheetah or not​

Answer 5

-gel electrophoresis separates DNA fragments by length
-the pattern of fragments produced will be different for different DNA like DNA in different organisms, like a fingerprint it will be unique for each individual
-saliva left on antelope will contain the DNA of whatever killed it
-this can be collected and amplified by PCR then gel electrophoresis can be carried out to produce a genetic fingerprint/electrophoretogram
-sample containing DNA can be collected from a cheetah and an electrophoretogram can be produced through PCR gel electrophoresis aswell
-the two electrophoretograms can be compared the more closely related two individuals are the more short tandem repeats theyll have in common & the more similar their DNA profiling and electrophoretogram will be, this will be shown on electrophoretogram as the larger STRs will be further from the anode

if they have enough similarities to be from the same species then the antelope was likely killed by a cheetah