Unit 1: DNA & The Genome - Key Area 2: DNA replication Flashcards
enzyme that adds free complementary DNA nucleotides during replication of DNA
DNA polymerase
technique used to separate macromolecules such as DNA fragments of different sizes
gel electrophoresis
enzyme from hot-spring bacteria used in PCR
heat tolerant DNA polymerase
DNA strand which is replicated in fragments
lagging strand
DNA strand which is replicated continuously
leading strand
enzyme that joins fragments of DNA to make the lagging strand
ligase
method of amplifying sequences of DNA in vitro
Polymerase Chain Reaction (PCR)
short complementary strand of DNA
Primer
formation of identical copies of DNA molecules
replication
DNA strand on which a complementary copy is made
template strand
define DNA replication
involves the production of two genetically identical strands of DNA
when does DNA replication occur?
prior to cell division (mitosis and meiosis)
what is DNA replication described as
semi-conservation as each daughter DNA molecule ends up with one of the original strands of the parental DNA and one newly synthesized strands.
what is the function of ‘helicase’ in DNA replication
causes DNA to unwind
what is the function of ‘ligase’ in DNA replication?
joins fragments of DNA on the lagging strand
what is the function of ‘DNA polymerase’ in DNA replication?
adds free nucleotides using complementary base pairing to the deoxyribose 3’ end of the new DNA strand that is forming
what are the requirements of DNA replication?
> original DNA template > free DNA nucleotides > DNA polymerase > primers > ligase
what is the function of a ‘primer’ in DNA replication?
binds to the 3’ end of the template DNA strand allowing DNA polymerase to add free nucleotides
what is the first step of DNA replication?
the double helix structure of DNA is unwound and hydrogen bonds between bases are broken to form two template strands
what is the second step of DNA replication?
two replication forks form and open the double-strand in opposite directions, exposing the bases
what is the third step of DNA replication?
A primer binds to each strand of DNA
what is the fourth step of DNA replication?
DNA polymerase adds DNA nucleotides using complementary base pairing to the deoxyribose 3’ end of the new DNA strand which is forming
what is the fifth step of DNA replication?
DNA polymerase can only add nucleotides in one direction, resulting in the leading strand being replicated continuously and the lagging strand being replicated in fragments
what is the sixth step of DNA replication?
Fragments of DNA are joint together by ligase
what is PCR (polymerase chain reaction) used for?
to amplify a desired DNA sequence
what are the requirements of PCR?
> nucleotides > primers > heat tolerant polymerase > template DNA > buffer > thermal cycler
why does PCR use primers?
Polymerase can only add nucleotides to an existing strand of DNA so PCR requires primers
why does PCR need two primers per cycle?
Because primers are short strands of nucleotides which are complementary to specific target sequences and there are two ends of the region of DNA to be amplified thus requiring two primers.
what is the first step of PCR?
Heating:
DNA molecule to be amplified is denatured by heating to between 92-98 degrees celsius, breaking hydrogen bonds between base pairs to separate the two strands
what is the second step of PCR?
Annealing:
DNA is cooled to between 50-65 degrees celsius to allow the primers to bind to target sequences
what is the third step of PCR?
Extension:
DNA is then heated to between 70-80 degrees celsius for heat-tolerant DNA polymerase to replicate the region of DNA
what is the fourth step of PCR?
two strands are formed and this cycle is repeated 30 times
how is DNA amplified in PCR?
in vitro (outside of a living organism)
what are the uses/ applications of PCR?
> paternity testing
crime scene analysis
diagnosis of genetic disorders
