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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