REPLICATION OF DNA Flashcards
State when DNA replication occurs and the role of DNA polymerase and primers
- DNA replication occurs prior to cell division.
- DNA polymerase is the enzyme that replicates DNA.
- DNA polymerase requires a primer to start DNA replication.
- A primer is a short strand of nucleotides which binds to the 3’ end of the template (parent/original) DNA strand.
- This allows DNA polymerase to add new nucleotides
Give examples of other molecules required for DNA replication
DNA replication requires the use of ATP, free DNA nucleotides and other enzymes throughout the process.
Describe the process of DNA replication
1) DNA is unwound and hydrogen bonds between bases are broken – forming two template strands.
2) Primer attaches to a short sequence on the DNA allowing the DNA polymerase to bind.
3) DNA polymerase will add nucleotides using the complementary base pairing rule to the deoxyribose (3’) end of the NEW strand which is forming
Describe the replication of the leading strand of DNA formed during DNA replication
- DNA polymerase works in a 5’ to 3’ direction. DNA polymerase can only add nucleotides to the 3’end of the growing strand
- This means that one strand is replicated continuously, and we call this the leading strand.
The replication of the lagging strand
- Due to the antiparallel structure of DNA the fact that DNA polymerase can only add nucleotides onto the 3’end, the opposite strand has to be replicated in fragments
- This is known as the lagging strand
- This requires the use of many primers and the fragments produced are joined together by the enzyme ligase
State the function of the polymerase chain reaction (PCR)
Polymerase chain reaction (PCR) amplifies DNA using complementary primers for specific target sequences.
describe the function of the primers used
primers are short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of DNA to be amplified
