KA2 DNA Replication&PCR

Question 1

State the steps for DNA replication.

Answer 1

1. DNA unwinds and hydrogen bonds between the bases are broken. DNA unzips and a replication fork is formed.
2. A primer is added at the 3’ to 5’ direction of the leading template strand. DNA polymerase adds free nucleotides continiously to form a new complementary strand.
3. Since nucleotides can only be added at the 3’ to 5’ direction, a primer is added as the replication fork widens. DNA polymerase adds nucleotides to form fragmnets.
4. These fragments are joined together by DNA ligase to form a new complementry strand.

Question 2

What is PCR?

Answer 2

Polymerase chain reaction is the amplification of DNA using primers which are complementary to the specifc target region.

Question 3

State the steps for PCR?

Answer 3

1. DNA is heated between 92 and 98 degrees celcius to sepetate the strands.
2. It is cooled between 50 and 65 degrees celcius to allow primers to bind to their specific target region.
3. It is heated etween 70 a d 80 degrees celcius to allow heat tolerant DNA polymerase to replicate the traget regions of the DNA.

Question 4

What do repeating cycles of heating and cooling in PCR allow?

Answer 4

It allows billions of copies of the target region of the DNA to be produced.

Question 5

Where is PCR useful?

Answer 5

It is useful in solving crimes, settle paternity suits and diagnose genetic disorders.