structure & replication of DNA Flashcards
describe the shape of DNA
double-helix
a DNA nucleotide is made up of what?
phosphate, deoxyribose sugar and a base
what is the sugar phosphate backbone?
a strong chemical bond that forms between the phosphate group of one nucleotide and the deoxyribose sugar of the next nucleotide that continues the length of the DNA molecule.
what are the base pairings?
adenine - thymine, guanine - cytosine
what type of bond binds the pairs together?
hydrogen bonds
the 2 strands that make up a DNA molecule run in opposite directions , what is the term to describe this?
anti-parallel
the phosphate is always at which end?
5’
the deoxyribose sugar is always at which end?
3’
the base sequence or the order in which the bases are in form the what?
genetic code
what is DNA polymerase?
an enzyme that is responsible for the synthesising new strands of DNA during replication.
what does DNA polymerase need to start the replication process?
primers
what are primers?
a short band of nucleotides which is formed at and binds to the 3’ end of the template DNA strand.
what does DNA polymerase do?
DNA polymerase adds DNA nucleotides, using complimentary base pairings to the deoxyribose 3’ end of the new DNA strand thats forming
what is ligase and what does it do?
ligase is an enzyme that joins together the fragments of the lagging strand of DNA.
what direction is the new strand built in?
5’—3’
what does the polymerase chain reaction do to DNA
it amplifies DNA
what are PCR primers and how are they designed?
short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of DNA to be amplified.
what are practical uses of PCR?
- to solve crimes
- settle paternity suits
- diagnose genetic disorders.
what enzyme is important to PCR and what role does it play?
PCR uses heat tolerant DNA polymerase with and its function is to join nucleotides to the 3’ end of the new strand.
what is heat tolerant DNA polymerase’s optimum temperature?
roughly 72 degrees celcius
how do they amplify the DNA region?
by a cycle of heating and cooling, the DNA is heated to between 92-98 to seperate the strands of DNA, it is then cooled to between 50-65 to allow the primer to bind to complementary target sequences , the heated back up to 70-80 so the heat tolerant DNA polymerase to replicate the region of DNA, this process is repeated and the DNA will be amplified
