Dear any a level bio teacher , please help me -Gel electrophoresis question

Question :
Describe how gel electrophoresis can be used to compare two samples of DNA . ( 6 marks )
(i) State 2 variables to be controlled.
(ii) Choose one of your variables and state how it is going to be controlled. State the effect that not controlling this variable has on the results of this investigation.

Please answer me, if you don't wanna give it easy to me, challenge me but answer me please.

Reply 1

macpatgh-Sheldon

20

Hi first part:
Mention for 6 marks (at least six of these):

a) DNA carries small charge
b) -ve because of PO3 groups
c) So move towards anode (+ve electrode)
d) Small fragments move faster
e) DNA cut into pieces with restriction endonuclease
f) Current turned on
g) DNA fragments move at different speeds depending on charge + size +shape
h) Current turned off.
i) Fragments made visible by adding probes
j) Probes have complementary base sequences
k) Probes also have radioactive isotope so visible on X-ray
l) INTERPRET: if bands are identical, DNA is from same person e.g. forensic medicine
m) If bands are similar, likely that two sources (e.g. persons) are related.

i) and ii) testing your knowledge of experimental technique - they teach you babies (sorrrry - 2nd time I am insulting you with the same 4-letter word [baby], Leah! :smile:

) these days by calling it "fair test". You can think of something to put down, I am sure!

Best,
M

(edited 4 years ago)

Reply 2

Leah.J

OP

13

Original post by macpatgh-Sheldon

Hi first part:
Mention for 6 marks (at least six of these):

a) DNA carries small charge
b) -ve because of PO3 groups
c) So move towards anode (+ve electrode)
d) Small fragments move faster
e) DNA cut into pieces with restriction endonuclease
f) Current turned on
g) DNA fragments move at different speeds depending on charge + size +shape
h) Current turned off.
i) Fragments made visible by adding probes
j) Probes have complementary base sequences
k) Probes also have radioactive isotope so visible on X-ray
l) INTERPRET: if bands are identical, DNA is from same person e.g. forensic medicine
m) If bands are similar, likely that two sources (e.g. persons) are related.

i) and ii) testing your knowledge of experimental technique - they teach you babies (sorrrry - 2nd time I am insulting you with the same 4-letter word [baby], Leah! :smile: