Transcription &
Translation
Protein Synthesis
Biology 12
Central Dogma

In nucleus


Produced in nucleus
Travels to cytoplasm

Produced in cytoplasm
Task

Complete the following table:
Transcription
Translation
Location
Template
(What is read)
Purpose
Outcome
(End result)
Definition: Transcription
Transcription
Nucleus
Location
DNA
Template
(What is read)
To change DNA into a form that
can make a protein
Purpose
Messenger RNA
(mRNA)
Outcome
(End result)
Definition: Translation
Translation
Location
Cytoplasm (by ribosome)
Template
(What is read)
mRNA
Purpose
Amino acids assembled in particular
order to make a protein
Outcome
(End result)
Protein (polypeptide)
Central Dogma
Task
Transcription & Translation
 Using pages 239/240

Make notes for EACH about:



Initiation (how it starts)
Elongation (how it is built)
Termination (how it ends)
Transcription
‘to copy’
Initiation:
 RNA polymerase binds to DNA @ ‘promoter’
Elongation:
 RNA polymerase builds mRNA


From DNA 3’ end
Uses complimentary base pairing

Remember: thymine (T) is replaced by uracil (U)
Transcription
‘to copy’
Termination:
 RNA polymerase reaches end of gene
 Stops transcribing
End Result:
 mRNA breaks away from DNA
 mRNA exits nucleus
Translation
‘new language’
Initiation:
 Ribosome binds to start codon
Turn to page 240!
Elongation:
 Ribosome moves along mRNA



From mRNA 5’ end
3 nucleotides = codon = amino acid
tRNA delivers proper amino acid
Translation
‘new language’
Termination:
 Ribosome reaches stop codon
 Stops translating
End Result:
 Ribosome falls off mRNA
 Protein (polypeptide chain) is released
Start and Stop Codons
Start Codon:
 Begins translation

AUG (universal start codon)


ALSO Codes for methionine (Met)
Sometimes GUG or UUG
Stop Codon:
 Ends translation

UGA, UAA, UAG
Page 240!
Transfer RNA (tRNA)




Delivers amino acid
to ribosome
Reads mRNA codon
Has a matching
‘anticodon’
One tRNA for each
amino acid
The
Whole
Picture
Next amino
acid to be
added to
polypeptide
Growing
polypeptide
tRNA
mRNA
Figure 6
(pg 239)
Example

DNA template:
3’ TAC ACA CGG AAT GGG TAA AAA ACT 5’

Complimentary DNA


mRNA codon


Read from DNA template (start reading at 3’)
tRNA anticodon


Read from DNA template (start reading at 3’)
Read from mRNA
Amino Acids (protein)

Read from mRNA
United Nations Conference
Who’s who?
 Mr. Na


Meri Boso


ribosome
Flash cards


mRNA
tRNA
Translation

protein
Task
A.
# 2, 4 – 6, 9 – 11
(page 241)
Omit “ribosomes” for #4
B.
#2
(page 249)
C.
# 3, 4 & 6
(page 254)
Task A:
#2 – Central Dogma

DNA makes RNA (mRNA)


through transcription
RNA makes proteins

through translation
#4 – RNA types

mRNA




Messenger RNA
End product of
transcription
Takes message from
DNA into cytoplasm
Used by ribosome to
make protein

tRNA



Transfer RNA
Delivers amino acid
to ribosome
rRNA


Ribosomal RNA
Helps form and
maintain ribosomes
#5 – DNA vs. RNA
DNA
RNA
 Sugar – deoxyribose  Sugar – ribose
 Double stranded
 Single Stranded
 Base pair – thymine
 Base pair – uracil
 Stays in nucleus
 Can leave nucleus
 Can replicate itself
 Cannot replicate
itself
 Longer strands
 Shorter strands
#6 – Transcription/Translation
Transcription
 Purpose:
 To make mRNA
from DNA
 Location:
 Nucleus
Translation
 Purpose:
 To make a
specific protein
from mRNA
 Location:
 Cytoplasm
(ribosome)
#9 – Stop vs. Start Codon
Start Codon
 mRNA code
 Tells ribosome to
begin translation
 Example:
 AUG
Also codes for
methionine
And: UUG, GUG


Stop Codon
 mRNA code
 Stops translation of
that specific amino
acid chain
 Examples:
 UAA, UAG, UGA
#10 – Transcribe to mRNA

DNA:
GGA TCA GGT CCA GGC AAT
TTA GCA TGC CCC AA

*mRNA*:
CCU AGU CCA GGU CCG UUA
AAU CGU ACG GGG UU
#11 – Translate to Amino Acids

mRNA sequence divided into codons:
GGC AUG GGA CAU UAU UUU GCC
CGU UGU GGU GGG GCG UGA

*Protein translation*:
Gly Met(start) Gly His Tyr Phe Ala
Arg Cys Gly Gly Ala (stop)
Task B:
#2 – Transcribe to mRNA

DNA:
TAC TAC GGT AGG TAT A

*mRNA*:
AUG AUG CCA UCC AUA U
Task C:
#3 – Anticodons
#4 – Change in 3rd Base May
Not Result in Error

Why not?


Amino acids have more than one codon
Example: proline



Codons CCU, CCC, CCA, and CCG
CC - always codes for proline
Third base/nucleotide does not matter
#6 – Translate to Amino Acids

mRNA:
GGC CCA UAG AUG CCA CCG GGA
AAA GAC UGA GCC CCG

*Protein translation*:
Met (start) Pro Pro Gly Lys Asp (stop)