electrophoresis

what is electrophoresis used for?

used to separate DNA fragments

are the wells placed at the positive or negative electrode? explain why?

negative electrode

→DNA fragments are negatively charged due to their phosphate groups

→DNA fragments are attracted to the positive electrode

method for conducting electrophoresis

-create wells in gel tray

-Place gel tray into tank

-add buffer solution

-place the DNA fragments into the wells at the negative electrode (cathode)

-Apply an electric current

-DNA fragments move towards the positive electrode.

-Smaller fragments move further than larger fragments

Why is a buffer/alkaline solution used in electrophoresis?

buffer solution carries current

how is DNA visualised in gel electrophoresis?

-fluorescent tags used→ DNA fragments are detected by UV light →helps visualise the bands formed

-radioactive tags

DNA fragments are separated by what?

DNA fragments are separated by length

→smaller fragments travel further as they have less mass so have less resistance in gel

→larger fragments move slowly

electrophoresis can also be used to separate mixtures of proteins. The gel contains a substance called SDS, which has a negative charge. SDS binds to proteins.

→Suggest why proteins are heated before being placed in the electrophoresis gel.

→Suggest why the binding of SDS to proteins is necessary for protein electrophoresis.

1st q

-Heating denatures the protein, exposing hydrophobic region

2nd q

-different proteins have different overall charges

-SDS binds to proteins to make all the proteins negatively charged

-proteins are separated by length/ mass only [not charge]

practice Q

note: in bio cathode is negative and anode is positive

Practice Q

Practice Q