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CHAPTER 12PROTEIN SYNTHESIS AND
MUTATIONS
-RNA-PROTEIN SYNTHESIS-MUTATIONS
PROTEIN SYNTHESIS
1. Who are the players?
2. What are the 3 processes?
3. Where in the cell do the processes occur?
4. How does each process work?
5. What is the product produced?
6. What if mistakes are made during the process?
DNA
Gene Protein
AA—AA—AA—AA Monomer?
Amino Acids
Bond?
Polymer?
Polypeptides range in size from a few monomers to thousands
Protein =
“Polypeptide”
“Peptide” Bond
Differences in ___ groups produce the ___ different amino acids
R20
Unique characteristics
3 bases = “Codon”
ACTGTTCGAGCTTATCodon Codon Codon Codon
Codon Amino Acid
Amino Acid Protein
1 GeneCodon
Genetic Code = “Universal Code”Same letters? Same words? = Different stories?
ATGC 20 Amino Acids
Where is DNA?
What makes Proteins?
2 Subunits
RNA?Ribo-Nucleic Acid
= Carry/Contain coded information for making proteins
“PROTEIN SYNTHESIS”
3 differences from DNA:
1. Generally single stranded
2. Uracil in place of Thymine (U not T)
3. Sugar is “Ribose”
3 Types of RNA:
messenger RNA (mRNA)
transfer RNA (tRNA)
ribosomal (rRNA)
DNA RNA Protein
PROTEIN SYNTHESIS
1
2
3
Protein/ polypeptide
64 Codons
20 Amino Acids
43
alanine - alaarginine - arg
asparagine - asnaspartic acid - asp
cysteine - cys glutamine - gln
glutamic acid - gluglycine - gly
histidine - his isoleucine
leucine - leulysine - lys
methionine - metphenylalanine -
pheproline - proserine - ser
threonine - thrtryptophan - trp
tyrosine - tyrvaline - val
DNA Code:
ACAGTTCGAGCTTATAmino Acids?
TranscriptionDNA mRNA
Initiation
Elongation
Termination
RNA Processing (Splicing)Avg length of Pre-mRNA is 8000 nucleotides long
Takes only about 1200 to code for an average sized protein of 400 AA
“Long noncoding stretches” that are not translated
Introns = noncoding segments (intervening)Exons = coding segments (expressed)
TRANSLATIONmRNA tRNA rRNA = Protein
tRNA = transfer AA from cytoplasm ribosome
tRNA = transcribed from DNA
tRNA
Amino Acid (end)Anticodon (end)
~80 nucleotidesFolds back on itself
H bonds
tRNA
Large and Small subunits“rRNA”
Structure/Function?
Ribosome
= bring mRNA together with tRNA (AA)
mRNA binding site
P site = holds tRNAcarrying the growing peptide chain
A site = holds tRNA carrying the nextamino acid to be added
E site = discharges tRNA’sleaving the ribosome
_
_
_
1. Initiation
guanine triphospate
Brings together mRNA and tRNA bearing the first AA (P site)
5’cap tells small unit to bindAUG initiation codon
methionine
Large subunitInitiator tRNA sits in P siteA site ready to receive
3’5’
Requires?
2. Elongation
AA added one by one
1. Codon recognitionIncoming tRNA binds to A site
2. Peptide bond between new AA’s
3. Translocation tRNA in A site P site tRNA in P site E site
mRNA moves 5’ end first
10th of a second
3. TerminationElongation continues until a stop codon reaches A siteUUA, UAG, UGA
Protein called a “release factor” binds directly to the stop codon in the A site
Polypeptide set “free”
UGGUUUUGAmRNA=
DNA?
tRNA?
Amino Acids?
Transcription
Translation
DNA
RNA
PROTEIN
Copy Drawing off Board
Protein Synthesis
• YouTube - The wonders of a tiny cell
MUTATIONS!!
WHAT HAPPENS WHEN A MISTAKE IS MADE IN CODING?
POINT MUTATIONS
•THE DOG BIT THE CAR
•= Misread a single base pairBase pair substitutions
•THE DOG BIT THE CAT
EpilepsyChromosome 6
Albinism
Frameshift Mutation
= add or delete a base
Insertions and Deletions
SchizophreniaDepressionChromosome 1
Color BlindnessRed/GreenX Chromosome
So why men?
Sex-Linked Mutations
CHROMOSOMAL MUTATIONS
• Part of chromosome broken off during Meiosis and rejoins incorrectly.
•Can have too many, or not enough
•Zygote usually dies
Down’s Syndrome = 47 chromosomes
Positive Mutations?
DNA, RNA, and MUTATIONS
-DNA-Watson and Crick-Sugar-Phosphate Backbone-Nucleotide-Nitrogen Bases (4)-Base Pairing-Complimentary Strand-Double Helix-Length of DNA
-Function of DNA-Codon-Amino Acids and Proteins-Genetic Code
-RNA-Differences from DNA-3 types-Protein Synthesis-Transcription-Translation
-Mutations-Point Mutations-Frameshift Mutations-Sex-Linked Mutations-Chromosomal Mutations-Positive Mutations