Translation and TranscriPtion
and Replication,Oh MY!
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d-*-\.- -
hor^r
Background
DNA is an exarnpieof a compiexbiological polymer called a nucleic acid, which is madeup of small subunitscalled nucleotides. The componentsof the DNA nucleotideare deoxyribose(a simple sugar),a phosphategroup, and a nihogen base.There
are four possiblenitrogenbasesin DNA-adenine (A), guanine(G), cytosine(C), and thymine (T). In DNA, the nucleotidespair
using hydrogenbonds to form a double strand.Becausethesetwo strandsare twisted, it is referredto as a double heiix. When
basepairs areformed, adeninewill only pair with thymine and guaninewill only pair with cytosine.
The mechanismby which DNA createsexact copies of all geneticinformation is called replication. The hydrogen bonds
betweenthe basesare brokenby an enzymewhich "unzips" the two strandsof DNA. Free nucleotidesfill in and form basepairs
that arebondedinto a chainby anotherenzyme.The result is two identicalcopiesof the DNA rnolecule.
DNA is only found in the nucleus.So,how is information broughtto the ribosomesfor protein synthesis?The answeris simple-by a single strandof RNA calledmessengerRNA (mRNA). RNA is composedof a singlestrandratherthan a double strand
as in DNA. RNA containsa sugarcalledribose,a phosphategroup, and four nitrogenbases.Ratherthan thymine (T), RNA conin DNA are madein the nucleus
tains uracil (U). MessengerRNA moleculesthat are complementaryto specific genesequences
by a processcalledtranscription.T\e geneticinformation from DNA is transcribedinto a singlestrandRNA "message"to be sent
from the nucleusto the ribosomesforprotein synthesis.
During protein synthesisat the ribosome,mRNA sequencesare read and translatedinto amino acids.The amino acids are
linked together into chains by enzymesto form proteins. The 20 amino acids are brought to the ribosomesby transfer RNA
(tRNA). Every threeniirogenbaseson a IRNA moleculeare called an anticodon.This anticodonmust matcha codon,thrpenirogen basesof the mRNA molecule,to translateinto an amino acid.An infinite variety of proteinscan be forlled from the 20 amino
acids,which can occur in any numberand in any order.
Maieriais
x 11",plain cr l-cm graph
Papeg8V.-"
Pencil
DNA is made-upof subunits
DNA falls into a groupof polymersknownasthe
is actuallva
. A deoxvribose
called
Nameandgivethe symbolfor the fourpossiblenitrogenbasesin DNA:
(
(
(_)
(_),
),
),
Name the type of bondsthat form betweenthe nucleotidepairs:
Definereplication(of DNA):
Name and give the abbreviation for the chemical messengerthat carries information from the nucleus to the
ribosomesin cytoplasmof the cell:
Tell how many strandsare found in RNA: _,
in DNA:
Name the DNA basethat is replacedwhen forming RNA:
Name the RNA basethat
replacesit:
Define transcription(of RNA):
that will be chained(in a given
MessenserRNA codesfor which of the
order) to make a more complex compoundcalled a
Tell how many amino acidsthere are:
Name and give the abbreviationfor the type or RNA that
gathersthe amino acids and makesthem available to the ribosomes
(_)
lTt
Preparation
l. Fold one sheet of paper in half
width-wise as shown in Fieure 1.
i i l
i i l
2 . Divide each side in half again by
folding
of the
should
folded,
each side backto the crease
original fold. The paper
have an "M" shape when
as shown in Figure 2.
Figur e 2 .
Figure 1.
3 . Lay the paper out in a landscape
orientation.
+.
Number *re paneis1-4 from left to right as shown
in Figure3.
2
3
4
) , Fold the papertogetherso that only panels1 and
4 are visible.
6 . On the edgeof panel I that touchespanel 4, write
the following DNA sequence(vertically).
Figure 4.
Figure 3.
A C C C T T C G A C G T A A C C G C A T
on theedgeof panel4 nextto the letteron panelI as shown on Figure 4.
DNA sequence
7. Now writethecomplementary
DNA sequence.
Theresultis a double-stranded
c
c
o
T
T
c
Procedure
Replication
3
4
1. Pull apart panels1 and 4 to expo$eall panels,as if'hnzipping" the double-stranded
DNA.
strandof mRNA on panel3 as shownin Figure8.
Each setof threemRNA basesis a codon.
4
T
i
:G
; G
j!
T
c rG
rC
,T
'G
orC
T'T
rT
,G
,G
C
I6
l;
Cl e
c ;G
c ; q
T
T
C
G , C
'T
'C
G
T
' T
r T
.L., c
! c
:c
:c
i o
;9
r
r
,
r
1
2. On panel 3 write the complementaryRNA strandfor the DNA on panel 1 as shownin
Figure ?. Nola: RNA doesnot containthymine; the complementarybasefor adenineis
uracil.
t . Draw a line under every third baseon the single
c
Figure 6.
l c
1. Fold panel 2 in half so that only panels1, 3, and 4 show (the creasebetweenpanels1
and 2 touchesthe creasebetweenpanels2 and 3) as shown in Figure 6.
Tlanslation
G
i
Tlanscription
z
^
s
T
2. On panel 2 write the complementaryDNA for panel 1 and
on panel 3 write the complementaryDNA for panel4 in the
Figure 5.
samemanneras completedfor step7 in the preparationsecDNA has now beenreplicatedto form
tion. SeeFigure 5. The original double-stranded
two identical double-stranded
DNA molecules.
3. Lay the paper out in a landscapeorientation.
The single strand on the left edge of panel 3 is
mRNA-label the strand"nRNA."
i
14
c
c
c
c
C
T
6
C
' T
' T
i, cg
,o
:T
,l
r i
2
3
A
' C
!
q
'
'
r
r
G
, G
U
T
T
c
c
:I
l'igure 7.
:i
,
a
c
4
:' xE
; !
Figure 8.
Write the complementary tRNA strand on the
edgeof panel2 next to the mRNA strandon panel 3-label this strand"IRNA:'
Figure 9.
3. Draw a line undereverythird baseon the single strandof IRNA on panel 2 as shownin Figure 9. Each set of threeIRNA
basesis an anticodon.
1 Division/Centimeter
46
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