1.2 Flashcards
what are dna strands composed of
repeating units called nucleotides
what does a nucleotide consist of
- a deoxyribose sugar
- a phosphate group
- a base
why are there 4 types of nucleotides
because there are 4 types of bases
how is the deoxyribose right of one nucleotide joined to the phosphate of another nucleotide
by a strong chemical bond
what do these repeating nucleotides make up
the sugar-phosphate backbone
what is the base pair rule
all bases have a complimentary base pair e.g. a+t, g+c
how are the 2 strands of dna held together
by weak hydrogen bonds
what is the meaning of anti parallel
the strands run in opposite directions
what does dna strands start and end with
each strand starts with a deoxyribose sugar at the 3’ end and ends with a phosphate at the 5’ end
what is the shape of dna
a double stranded helix
dna is the molecule of _______
inheritance
what does the base sequence of dna form
the genetic code
what does the base sequence determine
it determines the organisms genotype and phenotype
what does dna have to do before cell division
make an exact copy of itself
what does dna replication ensure
each of the two daughter cells formed have a full set of genetic info
and the diploid chromosome is maintained
stages of dna replication
- dna is unwound and hydrogen bonds between bases break to form two template strands
- dna is replicated by dna polymerase which needs primers to start replication
- a primer is a short strand of nucleotides which binds to the 3’ end of the template dna strand allowing dna polymerase to add nucleotides
- dna polymerase adds dna nucleotides using complementary base pairing, to the deoxyribose(3’) end of the new dna strand which is forming
- 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
- fragments of dna are joined by ligand
what way is the leading strand replicated
continuously
what way is the lagging strand replicated
in fragments / discontinuous
how are the fragments on the lagging strand joined together
by ligase
what does a primer do
binds to 3’ end of the template dna strand allowing dna polymerase to add dna nucleotides
what are the requirements for dna replication
- dna template strands
- primers
- a supply of dna nucleotides
- dna polymerase & ligase enzymes
- atp
what is pcr
pcr is a technique used to amplify a region of dna
what are the stages of pcr
- dna is heated to between 92°c and 98°c to separate the two strands
-it’s the cooled to between 50 and 65°c to allow primers to bind to the target sequence - it’s then reheated to between 70 and 80° for heat tolerant dna polymerase to replicate the region of dna
- repeated cycles of heating and cooling are used to amplify the target region of dna
what are the uses of pcr
- help solve crimes
- settle paternity disputes
- diagnose genetic disorders
