Question: 179: Refer to the following statements for agarose-gel electrophoresis :
(a) Agarose is a natural polymer obtained from sea-weed.
(b) The separation of DNA molecules in agarose-gel electrophoresis depends on the size of DNA.
(c) The DNA migrates from negatively-charged electrode to the positively-charged electrode
(d) The DNA migrates from positively-charged electrode to the negatively-charged electrode.
Choose the most appropriate answer from the options given below :
(1) (a) and (b) only
(2) (a), (b) and (c) only
(3) (a), (b) and (d) only
(4) (b), (c) and (d) only
Answer: Option (2)
Explanation:
Agarose is a natural polysaccharide polymer extracted from sea-weeds and is used to prepare the gel matrix, so statement (a) is correct.
In agarose-gel electrophoresis, DNA fragments are separated mainly on the basis of their size,
with smaller fragments moving faster through the gel pores, hence statement (b) is correct.
DNA molecules carry a negative charge due to the phosphate groups present in their backbone.
When an electric field is applied, DNA migrates from the negatively charged electrode towards the positively charged electrode, making statement (c) correct.
Statement (d) is incorrect because DNA does not migrate from positive to negative electrode.
Therefore, the correct statements are (a), (b), and (c), corresponding to option (2).