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Translation
Packet #11
Chapter #8
1
Introduction

Translation

The actual process of
protein synthesis where
the mRNA, made during
transcription, is utilized
along with ribosomes.
2
RNA Utilized During Translation
REVIEW, AND TYPES, OF RNA
3
Types of RNA
Continued…

tRNA



Transfer RNA
Transports amino acid molecules to
the ribosome
Class of small RNA molecules that
bear/carry specific amino acids to the
ribsome during translation

What are the building blocks of
proteins?



mRNA
Amino Acids
The amino acids will be used to
create a protein chain
rRNA
Types
of RNA
snRNA
rRNA



Ribosomal RNA
RNA found within the ribosomes
used during translation.
Two sizes

30S


tRNA
Large ribosome (subunit)
15S

Small ribosome (subunit)
4
Types of RNA
Continued…

mRNA

Messenger RNA



An RNA molecule
transcribed from the DNA of
a gene
Proteins are translated from
mRNA by the help of
RIBOSOMES
Carries the GENETIC
CODE, from DNA, used to
create proteins
mRNA
rRNA
Types
of RNA
snRNA
tRNA
5
THE RIBOSOMES
6
Ribosomes

Ribosome

Acts as the site of protein
synthesis in the cell

There are two sized
ribosomes used during
translation

Large


Small


30S
15S
The large subunit has
three sites



Attachment Site (A site)
Polypeptide Site (P site)
Exit Site (E site)
7
MRNA & THE GENETIC CODE
8
Introduction


mRNA carries the
genetic code in the form
of codons.
A codon is a group of
three nucleotides that
provide information
necessary for a single,
specific amino acid.
9
List of Codons & Amino Acids
10
TRNA AND THE GENETIC
CODE
11
The Role of tRNA


Recall that the role of tRNA is
carry individual amino acids to
the location where the polypeptide
chain is growing.
Hence, it must have something to
match the codon found on the
mRNA.

This is called the anticodon


A nucleotide triplet, found on
tRNA, that aligns with a
particular codon in the mRNA.
However, it MUST be noted that
the codon is the one that indicates
what the amino acid will be.
12
STEPS OF TRANSLATION
13
Introduction

There are five basic
steps during the process
of translation.





Initiation
Peptide Bond formation
Elongation
Translocation
Termination
Initiation
Peptide Bond Formation
Elongation
Translocation
Termination
14
Initiation

Ribosome binds to the mRNA


Initiator tRNA binds at start
codon




Start codon = AUG
tRNA carries anti-codon UAC
Initiator tRNA carries amino acid
MET
Ribosome binds to mRNA


Small subunit binds to mRNA
Large subunit binds to mRNA
Initiator tRNA will be located at
the P site of large subunit
15
Peptide Bond Formation

Ribosome (rRNA)
catalyzes the formation
of a peptide bond
between the new amino
acid and the carboxyl
end of the growing
polypeptide
16
Elongation

Elongation occurs when
the incoming amino
acid binds to the
polypeptide chain
through the formation of
a peptide bond.
17
Translocation





The ribosomes move
allowing the tRNA’s to
switch sites
tRNA in the A (addition)
site is translocated to the P
(polypeptide) site
tRNA in the E (exit site)
leaves the ribsome
mRNA shifts position
New tRNA with anticodon
enters the A site
18
Termination

Release factor (a protein)
binds at stop codon

There are THREE stop
codons






UUA
UGA
UAG
Polypeptide chain released
from tRNA
tRNA released from P site
Ribosomes released from
mRNA.
19
Special Note

As the polypeptide
chain is being
completed, attaches and
enters into another
organelle known as the
endoplasmic reticulum.

Hence creating what is
known as the rough
endoplasmic reticulum.
20
THE DANGER OF MUTATIONS
21
Introduction

Mutations occur when a
nucleotide base, or
nucleotide bases, has
either been changed,
inserted or deleted
within a gene.
22
Gene Mutations


When the base sequence of
a molecule of DNA is
altered, the sequence of
nucleotides for the mRNA
will also be altered.
This results in a change in
the amino acid sequence for
the polypeptide change and
hence changes a
protein/enzyme.
Mutation in gene
Change in mRNA
Change in the polypeptide
sequence
Change in the structure of a
protein/enzyme
Results in a severe consequence
for the human body.
23
TYPES OF MUTATIONS
24
Types of Mutations

Point Mutation

Change a single
nucleotide of a gene.
25
Types of Mutations

Frameshift Mutation


Addition or deletion of
one or more nucleotides.
Results in a change in
the improper grouping of
nucleotides in
subsequent codons.
26
Types of Mutations

Missense Mutation


The most common type of
mutation where the new
codon still codes for AN
amino acid (not necessarily
the same amino acid)
Nonsense Mutation

A mutation that changes an
amino acid codon to an amino
acid codon that is a stop
codon--usually resulting in a
shorter, and non-functional
form, of a protein
27
GENETIC DISORDERS
RESULTING FROM
MUTATIONS
28
Genetic Disorders

Frameshift Mutations

Huntington Disease


Cystic Fibrosis


Dominant allele disorder that
results in death by the age of
40
Autosomal recessive disorder
that results in excess
excretion of lung mucous
Hemophilia

X-linked recessive disorder
that results in the inability to
clot blood
29
Genetic Disorders II

Point Mutation

Skin Cancer

Proliferation genes have
nucleotide bases thymine
changed into uracil.


UV light rays that enter
skin cells.
This results in the
proliferation genes being
constantly turned on
30
REVIEW
31
Review I
Translation Process
Mutations
Initiation
Mutation in gene
Peptide Bond Formation
Change in mRNA
Elongation
Change in the polypeptide
sequence
Translocation
Change in the structure of a
protein/enzyme
Termination
Results in a severe consequence
for the human body.
32
Review II
Point
Missense
Types of
Mutations
Frameshift
Nonsense
33