AQA BIOL2 notes

There is a couple of gaps as I printed them out and drew diagrams for a single celled organism, the tissue fluid formation and what a B-glucose molecule looks like.

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  • Created on: 23-05-11 19:30
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BIOLOGY UNIT 2
DNA, Cell Division and Cancer
St
ruct
ure
of
DNA
DNA (deoxy
ribonucl
eic
aci
d)
along
w i
th
some
protei
n makes
up t
he chromosome s
in
eukar
yotes.
I
n pr
okaryot
es,
D NA molecul
es
are
sma ll
er,
ci
rcul
ar
an d
not
ass
o ci
ated
w i
th
prot
eins.
Gene:
a
speci
fi
c
sequence
of
bases
in
D NA
that
codes
for
a
pol
ypept
ide
The
gen et
ic
code
of
D NA
cont
rol
s t
he
order
of
ami
no
aci
ds
in
prot
eins
that
ar
e made
by
t
he cel
l'
s r
ibosomes.
How i
s DN A
str
uc tur
e
w el
l
s ui
ted
to i
ts
funct
ion?
i
t
is
stable
as i
t i
s a
d o uble
h el
ix
i
t
is
able
to
replicate itself
exactl
y whe n
cell
s di
vi
d e
i
t
is
compact as i
t
is
a dou bl
e heli
x
i
t
has a
precise genetic code w hi
ch can be
cop i
ed t
o cont
rol
pr
otei
n synt
hesi
s
DNA i
s ma de up
of
long
chains
call
ed
nucl
eoti
des A nucl
eoti
de i
s made up
of
t
hree part
s:
Deoxyribose (a
5 car
bon sugar)
A
n i
tr
oge ncontai
ning
organi
c base
(
ad eni
ne,
guani
ne,
thymi
ne
or
cyt
osi
ne)
A phosphate
group
Pur
ines:
adeni
ne
and guani
ne A
pur
ine
always
pai
rs
wit
h a
pyr
imi
dine.
Pyr
imi
dines:
t
hymine
and cyt
osi
ne
Nucl
eoti
des are
mo nome rs
that
j
oin
to
for
m pol
ynucl
eoti
de st
rands,
hel
d t
ogether
because
the
phosphate group of
one
nu cl
eoti
de
is
li
nked
to t
he sugar
of
the
next
by
st
rong
covalent bonds.
The
only
w ay
in
w hi
ch one pol
ynucleot
ide
chain
can
d i
ff
er
fr
om an ot
her
is
a
dif
fer
ent
sequence
of
the bases.
A
ch ange
in
sequ ence
of
ba ses
of
D NA coul
d r
esult
i
n a
non funct
ional
enzyme because
i
t
w oul
d change t
he pri
ma r
y st
ruct
ure so
change t
he hydrogen
/
ioni
c /
di
sulphi
de bonds
so
change the
tert
iar
y st
ruct
ure of
t
he enzyme so
the subst
rat
e cannot
bind
and no
E S
complexes
w i
ll
form.
Wat
son and
C r
ick
w or
ked out
t
he
str
uct
ure
of
D NA
when
they
compar
ed
the
quant
it
ies
of
t
he
four
bases
and f
o und:

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Page 2

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A and
T
found
in
same
propor
ti
on,
G
and C f
ound i
n same
propor
ti
on
fi
gures
always
equal
100% so no
other
bases ar
e pr
esent
The
two st
rands
of
nucl
eoti
des
in
D NA r
un i
n opposi
te
dir
ect
ions
and
twi
st
to
for
m a
doubl
e hel
ix.
The
bases
are
hel
d t
og et
her
by hydr
ogen bondi
ng.…read more

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Evi
dence
for
Semi
conser
vat
iv
e
Repl
icat
ion
Meselson
an d Stahl
used t
he E.coli
bact
eri
a which con t
ain
a si
ngle
circul
ar
DNA
mo l
ecule and
they
grew cult
ures
o f
15
t
hese cel
ls
in
a me dum cont
a i
ning N (
the
heavy
isot
ope ) so
all
t
he DN A became
15
l
abell
ed wit
h N .…read more

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Funct
ion
of
Mit
osi
s
I
ncr
eases
the
number
of
cel
ls
dur
ing
growth
Repl
aces
ti
ssue
dur
ing
repair
Al
lows
asexual reproduction
w hi
ch
produces
off
spr
ing
that
ar
e genet
ic
a l
l
y
i
dent
ical
t
o t
he
par
ent
Maintains the same chromosome number from one generation to the next
N B
bact
eri
a and
vir
uses
do
not
di
vi
de
by
mit
osi
s
The onl
y way…read more

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Prophase chr
omo somes coi
l
and condense
and
become
visi
ble
can
now
be seen
as 2 chr
oma t
ids
joi
ned at
t
he cent
rome r
e
nucl
ear
envelope
a nd
nucleol
us
disappear
s
cent
ri
oles
mo ve
to
op posi
te
pol
e s
of
t
he cel
l
Met
aphase chr
omo somes l
ine
up
i
ndependentl
y on
the
cel
l
equator
spi
ndle
fi
bres
have gr
own acr
oss
cel
l
chr…read more

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Funct
ion
of
spi
ndl
e:
att
ach
to
cent
romer
es
of
chr
omosomes
then
separ
ate
the
chromat
ids
Cyt
oki
nesi
s
Cel
ls
wit
hout
a
cel
l
w al
l
just
pi
nch
themsel
ves
in
two
and
a membr
ane
for
ms
in
the
mi
ddl
e of
t
he
cel
l
and
event
ual
ly
the
two
new daught
er
cel
ls
separ
ate
Cel
ls
wit
h a
cel
l
w al
l:
a
new cel
l…read more

Page 7

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D NA
compl
etes
the
cel
l
cycl
e so
cont
inues
to
divi
de
uncont
rol
led
cel
l
divi
si
on
produces
cancer
Cancer
ous cel
ls
div
ide
repeat
edl
y
and
uncont
rol
labl
e t
o f
orm
a mass
of
cel
ls
cal
led
a
t
umour or
neopl
asm.
Tumour
cel
ls
do not
r
espon d
to
nerve
signal
s and
hormones
as nor
ma l
heal
thy
cel
ls
woul
d.…read more

Page 8

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Speci
ati
on:
f
ormat
ion
of
a new
speci
es
Di
sconti
nuous
Var
iat
ion
Char
acter
ist
ic
s f
all
i
nto
a l
i
mit
ed
number
of
di
sti
nct
f
orms
wit
h no
int
ermedi
ates
e.g.…read more

Page 9

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Mut
agen:
r
adi
ati
on,
vi
ral
i
nfect
ion
or
chemi
cal
t
hat
i
ncr
eases
mut
ati
on
rat
e
Meiosis
I
n
me i
osis
there ar
e 2 nuclear divisions,
not
one
as i
n mitosi
s.
This
me ans
that
4 daughter cells ar
e for
me d from e ach
cel
l,
not
2.…read more

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Mi
t
o s
is
vs
Mei
osi
s
Mi
tosi
s Mei
osi
s
One
divi
si
on
of
the
cel
l Two
divi
si
ons
of
the
cel
l
Two
daught
er
cel
ls
are
for
med Four
daught
er
cel
ls
are
for
med
The
number
of
chr
omosomes
remai
ns
the The
number
of
chr
omosomes
hal
ves
same
No
crossi
ng
over
occur
s Crossi
ng
over
occur
s
Daught
er
cel
ls
have
ident
ical
Daught
er
cel
ls…read more

Comments

Hamza

AMAZING!

Izzzy

Ur a BABE thanks

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