Transcript Translation Definition - Mr. Barrow's Science Center

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Translation Definition
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Translation
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The actual process of protein synthesis where
mRNA, made during transcription, leaves the
nucleus, through nuclear pores located on the
nuclear envelope, and attaches to a ribosome
The production of a polypeptide (protein) whose
amino acid sequence is derived from codon
sequences
Put a star next to this--we will come back
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Playas of Translation
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RNA
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Ribonucleic Acid
A single stranded nucleic acid similar to DNA
Sugar is Ribose--not Deoxyribose that is found in DNA
Uracil replaces thymine as the nitrogen base
mRNA
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Messenger RNA
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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
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Playas of Translation II
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tRNA
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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
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What are the building blocks of proteins?
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Amino Acids
The amino acids will be used to create a protein chain
Ribosome
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Acts as the site of protein synthesis in the cell
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How do we form the Rough Endoplasmic Reticulum?
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Composed of Large subunits and small subunits
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When ribosomes bind to mRNA
Difference depends on type of rRNA
Has three sites (EPA)
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rRNA
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Large Subunits
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Contain 30S
Small Subunits
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Contain 15S
Please remember that the size of the ribosome is
determined by the amount of rRNA subunits
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Playas of Translation III
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rRNA
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Ribosomal RNA
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RNA that makes up the ribosomes
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Playas of Translation IV
Cracking the Genetic Code
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Codon
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A group of three neucleotides that provide the information necessary to
code for a single, specific amino acid
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A section of RNA (three nucleotide pairs in length) that encodes a
single amino acid
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AUG
UAG
Found on mRNA
Anticodon
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A nucleotide triplet, found on tRNA, that aligns with a particular codon
in the mRNA
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
Translation
Step A Initiation
All Biology Levels
Ribosome binds to the mRNA
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Initiator tRNA binds at start codon
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Start codon = AUG
tRNA carries anti-codon UAC
Initiator tRNA carries amino acid MET
Ribosome binds to mRNA
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Small subunit binds to mRNA
Large subunit binds to mRNA
Initiator tRNA will be located at the P site of large
subunit
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Steps A - E
Biology I & Biology I Honors
A. Initiation
B. Peptide Bond Formation
C. Elongation
D. Translocation
E. Termination
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Stop Codons are recognized
All playas are released
Where do the proteins go after they are finished
made?
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Step B
Peptide Bond Formation
Biology I Honors & AP Biology
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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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Step C
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Elongation
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Occurs when the incoming amino acid binds to the
polypeptide chain through the formation of a
peptide bond.
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Step D
Translocation
Biology I Honors & AP Biology
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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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Step E
Termination
Biology I Honors & AP Biology
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Release factor (a protein) binds at stop codon
Polypeptide chain released from tRNA
tRNA released from P site
Ribosomes released from mRNA
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Gene Mutations
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Discussed previously
When the base sequence of a molecule of
DNA is altered, the amino acid sequence of the
polypeptide for which it codes will likewise be
altered.
This affects the operation of enzymes
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Remember enzymes are created from proteins
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Mutations Continued
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DNA mutations
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Frame Shifts
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Addition of Nucleotides
Deletion of Nucleotides
Can result in genetic disorders previously discussed
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Huntington Disease
 This is how we get the dominant allele disorder
Cystic Fibrosis
 Autosomal recessive disorder
 Excess excretion of lung mucous
Hemophilia
 X-linked recessive disorder
 Inability to clot blood
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Types of Mutations
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Point Mutation
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Frameshift Mutation
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Mutation that occurswhen the number of nucleotides inserted or deleted
is not a multiple of three, resulting in the improper grouping of the
following nucleotides into codons
Missense Mutation
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Change a single nucleotide of a gene.
The most common type of mutation where the new codon still codes
for AN amino acid (not necessarily the same amino acid)
Nonsense Mutation
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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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Mutations Continued
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Substitution of Bases
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U for T in DNA
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UV rays, from sunlight, enters the skin cells
The proliferation genes, located on chromosomes
inside the skin cells, are mutated
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UV light rays
Thymine changes in Uracil
That results in the proliferation genes being
constantly turned on
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Initiation
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Translation
Step by Step
IPETT
Small subunit (ribosome) binds to the mRNA
Initiator tRNA binds at the start codon (AUG)
Large subunit (ribosome) binds on the mRNA
tRNA moves to the P site of the large subunit
Peptide bond formation
Elongation
Translocation
Termination (stop codons)
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