Polymerase Chain Reaction

Question 1

Polymerase Chain Reaction

Answer 1

• Developed by Kary Mullis
• It produces multiple copies of the same section of DNA
• This is known as DNA amplification
• It provides a larger DNA sample that can be worked with
• This is useful in both research (to amplify a gene quickly to allow it to be sequenced to detect a possible mutation and in forensics when only a small sample of DNA is obtained)

Question 2

The Process - Step 1

Answer 2

• DNA is denatured (split into 2 strands) by heating it to 95 degrees celsius

Question 3

The Process - Step 2

Answer 3

• A short section of DNA which contains complementary bases to the start of the DNA to be copied is added
• This is called a PRIMER
• This will bind to the DNA (a process called ANNEALING) and start the copying of the DNA
• In order for this to happen, the solution is cooled to 55 to 65 degrees celsius (to prevent further denaturing)

Question 4

The Process - Step 3

Answer 4

• Free DNA nucleotides are added along with DNA polymerase
• The most common enzyme is called TAQ polymerase. This enzyme is derived from bacteria that live in a hot environment. This allows the enzyme to be heated to high temperatures required to denature the DNA without itself being denatured
• DNA replication then occurs using the supplied free nucleotides

Question 5

The Process - Step 4

Answer 5

• By the end of step 3, the sample of DNA has doubled
• These steps are then repeated approximately 30 times, doubling the quantity of DNA at the end of each process
• This results in millions of copies of the DNA being produced in a relatively short period of time