Question

In agarose gel electrophoresis of a sample of DNA,

A) small DNA fragments in the sample will move more rapidly through the gel than large DNA fragments.

B) the DNA will move through the gel toward the positive electrode.

C) the higher the concentration of agarose in the gel, the more rapidly will the DNA move through the gel.

D) A and B

E) all of the above

Answer 1

Ans.

• Gel electrophoresis is a commonly used lab technique to seperate charged molecules such as nucleic acids (DNA & RNA) and proteins depending upon their size.
• Upon the application of an electric current, charged molecules migrate through the gel.
• The gel acts as a sieve like matrix, facilitating the movement of charged particles upon passing an electric current.
• During the running of gel, one end is positively charged whereas second end is negatively charged.
• The size of the DNA fragments to be run in the gel electrophoresis, determines the concentration of agarose gel to be used.
• As a general rule,  the lower the concentration of agarose in the gel, the more rapidly will the DNA move through the gel and the higher the concentration of agarose in the gel, the more slowley will the DNA move through the gel.
• Migration of charged molecules takes place towards the end with opposite charge.
• DNA segments of different length can be distinguished through the gel electrophoresis.
• Since, seperation of molecules occurs according to their size, so small DNA fragments in the sample will move more rapidly through the gel than large DNA fragments.
• Upon the application of electric current, negatively charged DNA will move through the gel toward the positive electrode.
• Dyes can be used to visualize the DNA on the gel once it got seperated.
• A marker DNA of identical size is usually also run at the same time through the gel acting as a standard and upon comparison of sample DNA with the marker DNA, size of sample DNA fragment can be determined.