gel electrophoresis

Question 1

why do people do it

Answer 1

to sort and measure DNA strands according to lengths

Question 2

why is DNA negatively charged

Answer 2

because of the phosphate groups in the backbone of the molecule

Question 3

how does dna move through gel

Answer 3

electric current is passed through gel, since DNA is negatively charged, the fragments are repelled by a negative charge attracted by a positive charge

Question 4

procedure
1

Answer 4

RE cut DNA into fragments

Question 5

procedure
2

Answer 5

DNA sample is placed in a well at the top of a gel.
gel is porous- it has tiny holes so that dna fragments can squeeze through

Question 6

procedure 3

Answer 6

electric current is passed through.

smaller fragments can squeeze through more easily, so they move the fastest and furthest along the gel (larger fragments are opposite).

Question 7

procedure 4

Answer 7

DNA ends up forming bands in the gel at different locations, depending on the different locations, depending on the size and number of fragments

Question 8

how to know fragment size

Answer 8

is determined by “running” a known DNA sample beside well so the band locations can be compared.

results of the know sample creates a “ladder” with bands at known lengths measured in bp

Question 9

how to make it visible

Answer 9

ethidium bromide under UV light
- simplest method is to dye the DNA with a molecule that will attach to the DNA and can be seen.