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HIGHER BIOLOGY
Unit 1
1.1 + 1.2 - Structure and Replication of DNA
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Cards (49)
A?
phosphate
B?
deoxyribose sugar
C?
base
How is the sugar and phosphate bonded in DNA structure?
strong covalent bond
How are the bases held together in DNA structure?
weak hydrogen bond
Leading
strand runs from 5’ to 3’
Lagging
strand runs from 3’ to 5’
DNA can be described as
antiparallel
Define DNA structure?
a double stranded helix with anti parallel strands
The
base sequence
of DNA forms the genetic code
Adenine
bonds to thymine
Cytosine
bonds to guanine
What is a prokaryote?
organisms that do not have a
membrane bound nucleus
(
bacterial
cells)
What is a eukaryote?
organisms that have a
membrane bound nucleus
(
animal
,
plant
,
fungal
)
How is DNA arranged in prokaryotes ?
one circular chromosome
smaller circular plasmids
to contain
extra
genes
How is DNA arranged in eukaryotes?
linear
chromosomes in the nucleus packaged with
histones
to prevent
tangling
circular
chromosomes in
mitochondria
and
chloroplasts
yeast
also has
plasmids
define dna replication ?
process
where
DNA
makes an
identical copy
of
itself
dna replication always precedes
mitosis
What 5 things are required for dna replication?
DNA template
enzymes
(
DNA polymerase
)
ATP
DNA nucleotides
Primers
what is the function of a primer?
to
initiate DNA replication
what is a primer?
a
short strand
of
nucleotides
which binds to the
3’
end of the
template
DNA strand
What is the first stage of DNA replication?
double helix
is
unwound
by the enzyme
helicase
stage 2 of DNA replication ?
hydrogen bonds
break between
bases
to form 2
template
strands and a
replication fork
is formed
A?
leading
strand
B?
lagging
strand
What direction does DNA polymerase add DNA nucleotides in?
3’
to
5’
the leading strand of DNA is replicated
continuously
The lagging strand of DNA is replicated in
fragments
why is the lagging strand replicated in fragments?
DNA nucleotides must be added from the
3’
end
What happens during stage 3 of DNA replication?
primers initiate DNA replication by
binding
to the
3’
end of the
leading
strand and at several sites of the
lagging
strand
What happens during stage 4 of DNA replication?
DNA
polymerase
adds free DNA nucleotides continuously to the
3’
end of the
lead
strand in fragments to the
3’
end of the
lag
strand
what happens during stage 5 of dna replication?
fragments of DNA in
lag
strand joined together by
ligase
what is PCR (Polymerase chain reaction)?
a laboratory technique used to
amplify
DNA using complimentary
primers
for specific
target
sequences
What apparatus is used in PCR?
Thermocycler
What are the 3 stages of PCR?
Denaturation
,
annealing
,
extension
stage 1 of PCR?
DNA
is heated between
92
and
98
°C to
separate
the strands
stage 2 of PCR?
DNA
is cooled to between
50
and
65
°C to allow
primer
to bind to
target
sequences
stage 3 of PCR?
DNA is heated to between
70
and
80
°C for
heat-tolerant
DNA
polymerase
to
replicate
the region of
DNA
A?
DNA
denaturation
B?
primer annealing
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