Question

2. In an agarose gel containing ethidium bromide, rRNA can be located by its fluorescence, but mRNA cannot. Briefly explain.

Answer 1

IN Agarose gel with Ethidium bromide ,the ethidium bromide acts as intercalating agent.It usually helps in detecting double stranded nucleic acids(LIKE DNA) and later it should be exposed to UV light ,it will fluoresnce with orange colour emission .

Double stranded(DNA) can be clearly seen due to its more calcificaton and more staining compared to RNA.

Although t RNA,m RNA and r RNA have single stranded areas in internal structure and also have double helices ,which in this scenerio tRNA and rRNA are a substantial part of whole molecule,all 3 stain with ethidium bromide,but not quietly as strong as DNA.

In agarose gel our size markers are inacurate for sizing RNA( because it is availble in different complex structures) but stains less reasonable than DNA.

but m RNA is also a complex in mixture of sizes,so it runs as a smear,without much RNA or staining at any given size.

soooo in that scenerio if we have purified messenger RNA ,RAHER THAN total RNA it lacks prominent bands and is hard to see.