Translation Packet #11 Chapter #8 1
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1
Translation
Packet #11
Chapter #8
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Introduction
Translation The actual process of
protein synthesis where the mRNA, made during transcription, is utilized along with ribosomes.
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REVIEW, AND TYPES, OF RNARNA Utilized During Translation
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Types of RNAContinued…
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?
Amino Acids The amino acids will be used to
create a protein chain rRNA
Ribosomal RNA RNA found within the ribosomes
used during translation. Two sizes
30S Large ribosome (subunit)
15S Small ribosome (subunit)
Types of RNA
mRNA
snRNA
tRNA
rRNA
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Types of RNAContinued…
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
Types of RNA
mRNA
snRNA
tRNA
rRNA
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THE RIBOSOMES
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Ribosomes Ribosome
Acts as the site of protein synthesis in the cell
There are two sized ribosomes used during translation
Large 30S
Small 15S
The large subunit has three sites
Attachment Site (A site) Polypeptide Site (P site) Exit Site (E site)
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MRNA & THE GENETIC CODE
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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.
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List of Codons & Amino Acids
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TRNA AND THE GENETIC CODE
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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.
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STEPS OF TRANSLATION
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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
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Initiation
Ribosome binds to the mRNA Small subunit binds to 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
Large subunit binds to mRNA Initiator tRNA will be located at
the P site of large subunit
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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
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Elongation
Elongation occurs when the incoming amino acid binds to the polypeptide chain through the formation of a peptide bond.
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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
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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.
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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.
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THE DANGER OF MUTATIONS
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Introduction
Mutations occur when a nucleotide base, or nucleotide bases, has either been changed, inserted or deleted within a gene.
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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.
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TYPES OF MUTATIONS
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Types of Mutations
Point Mutation Change a single
nucleotide of a gene.
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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.
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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
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GENETIC DISORDERS RESULTING FROM MUTATIONS
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Genetic Disorders
Frameshift Mutations Huntington Disease
Dominant allele disorder that results in death by the age of 40
Cystic Fibrosis Autosomal recessive disorder
that results in excess excretion of lung mucous
Hemophilia X-linked recessive disorder
that results in the inability to clot blood
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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
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REVIEW
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Review I
Translation Process Mutations
Initiation
Peptide Bond Formation
Elongation
Translocation
Termination
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.
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Review II
Types of Mutations
Point
Frameshift
Nonsense
Missense
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