unit 1 key area 2 Flashcards
(21 cards)
when does DNA replication occur
before a cell divides
what does DNA replication ensure
an exact copy of a species genetic information is passed on from one cell to another during growth
what are the requirements for DNA replication
DNA, primers, nucleotides, DNA polymerase, DNA ligase and ATP
what is a primer
a short strand of nucleotides that binds to the 3’ end of the template allowing polymerase to add nucleotides
what is DNA polymerase
enzyme which adds nucleotides. it can only add complimentary nucleotides in one direction to the 3’ end
what is DNA ligase
joins fragments of the lagging strand
what is stage 1 of DNA replication
DNA is unwound (by DNA
Polymerase) and weak hydrogen bonds between bases
break to form 2 template strands.
what is the point of separation called
replication fork
what is stage 2 of DNA replication
a primer attaches to the 3’ end of the strand of to be replicated by DNA polymerase
what is stage 3 of DNA replication
DNA polymerase can now add free complimentary nucleotides to the 3’ end of the primer and the new (leading) strand forms continuously
what is stage 4 of DNA replication
the opposite strand is replicated in fragments as the DNA strand unzips. this is called the lagging strand
what is stage 5 of DNA replication
DNA ligase joins the fragments on the lagging strand
what is PCR
when DNA fragments are amplified through repeated cycles of artificial replication using complementary primers for specific target sequences.
what happens to the number of DNA fragments after one cycle
it doubles
what does the process of PCR involve
cycles of heating and cooling which amplifies the target region of DNA
what is required for PCR
heat tolerant DNA polymerase, DNA template, primers, pH buffer and 4 types of DNA nucleotide
what is stage 1 of PCR
double stranded fragment heated to 92/98 degrees to break hydrogen bonds between bases and separate the two strands
what is stage 2 of PCR
the now separated strands are cooled to 50/65 degrees to allow primers to anneal to complimentary target sequence
what is stage 3 or PCR
it is now heated to 70/80 degrees so heat tolerant DNA polymerase can replicate the region of DNA by adding primers to 3’ end
what happens after stage 3 of PCR
the cycle is repeated
what are the practical applications of PCR
- forensics - analyse minute traces of blood/other tissues
- diagnostically - diagnosis of genetic diseases/disorders
- paternity suits - to identify the father of a child
