Question

1a) A band on an electrophoresis gel corresponds to _____

Choices:

- the size standard

- millions of fragments of the same size

- a DNA fragment of a particular size

- the blue tracking dye

b) What is the function of the size standard?

Choices:

- it allows the researcher to calculate the unknown sizes of the DNA fragments by comparing then to then known sizes.

- it marks the location where the fragments should line up.

c) Longer fragments of DNA move through a gel faster then short fragments, because they contains more negatively charger phosphates.

Choices:

-true

-false

Answer 1

Gel electrophoresis is a method which separates DNA based on the size using electric charge across a porous gel.

1a.
A band on an electrophoresis gel corresponds to a DNA fragment of a particular size.
The size is inferred based on the marker DNA(Size standard).
OPtion c is the answer.

b.
Size standard otherwise known as marker DNA allows one to calculate the unknown sizes of the DNA fragments by comparing it to
the marker DNA.
It contains DNA of different sizes which is spread like a ladder.

c.
Shorter DNA move faster than longer DNA.
Shorter DNA are at the base of the gel and longer DNA are the top of the gel and move slowly.
DNA fragments are negatively charged hence they move towards anode.
As all DNA fragments have same amount of charge per mass shorter DNA move faster than long DNA.
Hence the given statement is FALSE.

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