Question

In the DNA isolation procedure, ice-cold 95% ethanol was added to the tube that originally contained a thin piece of beef liver. Why is the ethanol added? Why is ice-cold ethanol used instead of room temp?

a) To facilitate DNA replication
b) To denature proteins
c) To precipitate DNA
d) To inhibit enzymatic activity

Answer 1

Ethanol is used in DNA isolation to precipitate DNA from the solution and ice-cold ethanol is particularly effective because it also inhibits enzymatic activity that can degrade DNA.

Step-by-step explanation:

In the process of DNA isolation, ethanol is added to the tube containing a thin piece of beef liver to precipitate DNA from the solution. The use of ice-cold ethanol also helps to inhibit enzymatic activity that could degrade the DNA. When ethanol is added, the DNA, which is less soluble in ethanol, especially when it is cold, forms viscous strands that can be spooled on a glass rod. The low temperature of the ice-cold ethanol further promotes DNA precipitation and prevents the dissolution of DNA, as well as slows down the activity of DNases, enzymes that could otherwise digest the DNA.