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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…

Page 2

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same
percent
age of
puri
nes
as pyr
imi
d i
nes.


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…

Page 3

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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…

Page 4

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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…

Page 5

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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…

Page 6

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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…

Page 7

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t
he
p53
gene
codes
for
pr
oduct
i
o n
of
the
p53
prot
ein

mut
ati
on
of
the
p53
gene
means
no
p53
prot
ein
is
made

t
he
cel
l
wit
h t
he
damaged
D NA
compl
etes
the
cel
l
cycl
e so
cont…

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.
ABO
bl
ood
group
syst…

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…

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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…

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Hamza

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