Key Area 1.2: Replication of DNA Flashcards
Why do cells need to copy their DNA?
DNA must be copied during mitosis to make sure that new cells have the same number of chromosomes to ensure that all cells have same genes
What happens in the first stage of DNA replication
the first step is for the hydrogen bonds holding the bases together to break, in turn separating the two strands
What happens at the second stage of DNA replication
In the second of DNA replication is free nucleotides begin to line up with complementary nucleotides
What happens at the third stage of DNA replication
The third and final step to DNA replication is that Sugar-Phosphate bonds form, now two DNA molecules that are identical to the singular parental molecule have been formed
What is DNA polymerase role in DNA replication
The enzyme DNA polymerase controls the formation of the sugar-phosphate bonds when making the new strand of DNA, the polymerase adds free complementary DNA nucleotides so that complementary strands synthesise continuously.
What are the requirements for DNA replication
the requirements for DNA replication is
- DNA template
- DNA nucleotides (4 different types)
- primers
- source of energy (ATP)
- DNA polymerase and ligase
Replication on the leading strand
-DNA polymerase can only join nucleotides onto the 3’ end and no other
this means
-hydrogen bond breaks and the DNA has unzipped
-primer can attach itself onto the start of the DNA being copied, it then adds free nucleotides onto the end of the primer.
- This same process continues on until the leading strand has been fully copied
Replication of the lagging strand
DNA polymerase can only add onto the 3’ end of a primer.
- Many primers are attached along this strand
- These lagging strands are extended by the DNA polymerase
- The fragments are then joined by the enzyme ligase
- This would be known as a discontinuous process
What are the requirements for PCR
- Primers
- Supply of nucleotides
- Ph buffer
- mg2-DNA polymerase co-factor ( makes it work better)
