1.2 Flashcards
what are individual units of dna called
nucleotides
what makes a nucleotide
a phosphate
deoxyribose sugar
a base
what are the four different bases
adenine
guanine
thymine
cytosine
what is determined by dna
what genes are expressed
what holds bases together
hydrogen bonds
what are nucleotides held together by
strong covalent bonds
what carbon is phosphate found at
5
what carbon is the deoxyribose at
3
what is the structure of dna
a double stranded helix, two strands lying side by side running in opposite directions they are antiparallel
what are the stages of dna replication
- DNA is unwound and unzipped, hydrogen bonds are broken between bases
- DNA polymerase adds free nucleotides working in a 3 to 5 direction
3.fragments are joined by ligase
what is a primer
short strand of nucleotides which bind to the 3 end of the dna strand allowing dna polymerase to add nucleotides
how is the leading strand made ( 3’ to 5’ )
it is made continuously
how is the lagging strand made
nucleotides can not be added to the 5 end because dna polymerase can only work 3 to 5 so it is made in fragments
what is needed for dna replication
dna
ligase
primers
free nucleotides
dna polymerase
what does amplification of dna mean
increasing the amount of dna
what is pcr used for
allows scientists to make millions of copies of dna to analyse
what do you need for pcr
dna
complementary primers
thermal cycler
heat tolerant polymerase
supply of nucleotides
why does the polymerase need to be beat tolerant
must be able to withstand the temperatures used
what are the stages of pcr
- dénaturation - DNA is heated to 92-98c to separate the strands
- annealing - it is cooled to 50-65c to allow primers to bind
- extension - heated to 70-80c for heat tolerant dna polymerase to replicate the dna
what is pcr used for
solving crimes
diagnosing genetic disorders
paternity tests
