Objectives
►I
know what a gene is
► I can describe the process of protein
synthesis
► I can describe the functions of the three
types of RNA
► I can predict the protein that will be made
from a strand of DNA
Protein
Structure
GENES
NUCLEUS
DNA BLUEPRINTS
DNA HAS TO SEND A MESSAGE
HOW IS DNA GOING TO TELL THE
RIBOSOMES WHAT TO MAKE?
RIBOSOMES
CYTOPLASM
MAKES PROTEINS
Protein Synthesis
TRANSCRIPTION
TRANSLATION
AA
“WRITE THE
MESSAGE”
DNA
AA
AA
“DECODE THE
MESSAGE”
mRNA
PROTEIN
AA
NUCLEUS
AA
DNA REPLICATION
&TRANSCRIPTION
TRANSCRIPTION
AA
AA
AA
CYTOPLASM
TRANSLATION
RIBOSOMES
RNA – THE MESSAGE
A
U
C
G
U
DNA
RNA
U
A
T
A
T
C
C
G
G
A
T
U
C
G
A
D
R
RNA
A. Ribonucleic Acid
i. Single stranded
ii. Has ribose sugar
iii. Has Uracil instead of Thymine
B. Bonding Pattern
i. A - U
ii. C - G
3 types of RNA
i. mRNA – messenger RNA – carries
DNA “message” from the nucleus to
the rest of the cell
ii. tRNA – transfer RNA – brings or
“transfers” amino acids from the
cytoplasm to the ribosomes to
assemble proteins
iii.rRNA – ribosomal RNA – helps
make up ribosomes
Making Proteins: 2 steps
1.
Transcription = re-writing the instructions
from the language of DNA to the language
of RNA
 WHY? Because DNA is too large to leave the
nucleus, but mRNA can slip out through the
nuclear pores
2.
Translation = de-coding the message
(mRNA CODES for Amino Acids)
Transcription – making of mRNA
A. Copy part of DNA into complementary
RNA strand “Writing of RNA using DNA”
B. RNA polymerase – enzyme that binds to
DNA to use as template and assemble
RNA nucleotides
i.
Binds to region of DNA called the ‘promoter’
which tells the enzyme where to start
ii. RNA polymerase releases DNA strand when
RNA strand is complete
C. mRNA will then travel into cytoplasm
DNA is TRANSCRIBED into mRNA
D
A
U
R
D
G
C
R
C
G
R
A
U
R
T
A
R
D
D
D
Transcribe this DNA sequence
►CATGACTAG
►GUACUGAUC
Protein Synthesis
TRANSCRIPTION
TRANSLATION
AA
“WRITE THE
MESSAGE”
DNA
AA
AA
“DECODE THE
MESSAGE”
mRNA
PROTEIN
AA
NUCLEUS
AA
DNA REPLICATION
&TRANSCRIPTION
TRANSCRIPTION
AA
AA
AA
CYTOPLASM
TRANSLATION
RIBOSOMES
TRANSLATION
The process of translating or decoding the
DNA message (mRNA) into amino acid
chains (proteins)
tRNA
A.
B.
i.
tRNA have 3 bases on them called an
anticodon which pairs with the codon of the
mRNA
ii. Each tRNA adds one amino acid that it has
brought from the cytoplasm making the
protein chain longer
tRNA – cloverleaf shape
UGC
ANTICODON
RIBOSOMES
AA
tRNA
mRNA
U A C
AA
G U A
AA
A U G
AA
A C U
AUGCAUUACUGA
CODON
Steps of Protein Synthesis
1.
2.
3.
4.
mRNA leaves nucleus and attaches to
ribosomes
tRNA with the anticodon UAC attaches to
the mRNA start codon AUG to begin
protein chain with amino acid methionine
Additional tRNA’s add other amino acids to
the protein chain connecting them with
peptide bonds
Protein synthesis continues until it reaches
a stop codon (UGA, UAA, UAG)
Genetic Code
A.
B.
C.
D.
Proteins are built from different
combinations of 20 amino acids
AA sequence is determined by sequence of
bases in mRNA
Each 3 base codon “codes” for a different
amino acid
64 possible codons
A. 61 code for 20 amino acids
B. 3 are “Stop” codons
How do we know what Amino Acid
to add?
USE THE mRNA
CODE TO TRANSLATE
INTO AMINO ACID’S
mRNA – 1) AUG
2) CAU
3) UAC
4) UGA
RIBOSOMES
MET
MET
tRNA
mRNA
U A C
MET
HIS
G U A
HIS
TYR
A U G
A C U
AUGCAUUACUGA
CODON
PRACTICE
► DNA
:TACGACGTAAAAACT
► mRNA:
?
► tRNA:
?
► Amino
Acid Sequence:
?
PRACTICE
► DNA
: TAC-GAC-GTA-AAA-ACT
► mRNA: A U G - C U G - C A U - U U U - U G A
► tRNA:
UAC-GAC-GUA-AAA-ACU
► AA Seq: MET - LEU - HIS - PHE
DNA Replication
A
T
A
T
C
G
A
T
C
G
DNA TRANSCRIPTION
D
A
U
R
D
G
C
R
C
G
R
A
U
R
T
A
R
D
D
D
DNA
mRNA
NUCLEUS
DNA REPLICATION
&TRANSCRIPTION
TRANSCRIPTION
AA
AA
AA
AA
RIBOSOMES
CYTOPLASM
TRANSLATION
PRACTICE
► DNA
:
TAT – CGC – AGC
► mRNA:
AUA – GCG - UCG
► Amino Acid Sequence: Ile Ala - Ser