Transcript Protein Synthesis

Protein Synthesis
Transcription
You’re made of meat, which is
made of protein.
Transcription
 “Something written,
especially copied from one
medium to another, as a
typewritten version of
dictation.”
 Enzymes make an RNA copy
of a portion of DNA.
 The “message” from DNA is
transcribed as RNA.
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Transcription
A
DNA
strand
RNA
strand
RNA
strand
C
B
DNA
strand
Transcription
 Prokaryotic cells, no
nucleus, mRNA made
in cytoplasm.
RNA Processing
 Not all nucleotides in DNA codefor
proteins.
 Contain non-coding sequences,
called introns.
 Kind of like ads in a magazine (not
really information you need to read the
magazine articles.)
RNA Processing
 Regions containing protein
code called exons because
expressed.
 Only about 5% of DNA is
exons.
 Introns partly “junk” and partly
serve regulatory functions.
RNA Processing
Both introns and
exons are
transcribed.
Introns must be
removed before
mRNA can code for
a protein.
RNA Processing
 Enzymes cut out
introns and paste
exons back together.
 Like removing all the
ads from a magazine.
 mRNA leaves
nucleus goes to
ribosomes.
The Genetic Code
Codon - Three nitrogenous bases in mRNA
code for one amino acid.
 DNA - GAG CAT TAG ACT TAC GAT GAC
 mRNA - CUC GUA AUC UGA AUG CUA CUG
The Genetic Code
How many possible combinations of
nucleotides are there in a 3 nucleotide
Codon?
Each base can be used more than once
Different orders of combinations count as
different (AAC is different from CAA)
4 x 4 x 4 = 64
The Genetic Code
The Messenger RNA Genetic Code
First
Letter
U
U
Phenylalanine (UUU)
A
G
Third
Letter
G
Serine (UCU)
Tyrosine (UAU)
Cysteine (UGU)
Serine (UCC)
Tyrosine (UAC)
Cysteine (UGC)
Leucine (UUA)
Leucine (UUG)
Serine (UCA)
Stop (UAA)
Stop (UGA)
Serine (UCG)
Stop (UAG)
Tryptophan (UGG)
Leucine (CUU)
Proline (CCU)
Histadine (CAU)
Arginine (CGU)
Leucine (CUC)
Proline (CCC)
Histadine (CAC)
Arginine (CGC)
Leucine (CUA)
Proline (CCA)
Glutamine (CAA)
Arginine (CGA)
Leucine (CUG)
Isoleucine (AUU)
Proline (CCG)
Glutamine (CAG)
Arginine (CGG)
Threonine (ACU)
Asparagine (AAU)
Serine (AGU)
Isoleucine (AUC)
Threonine (ACC)
Asparagine (AAC)
Serine (AGC)
Isoleucine (AUA)
Methionine;
Start (AUG)
Threonine (ACA)
Lysine (AAA)
Threonine (ACG)
Lysine (AAG)
Arginine (AGA)
Arginine (AGG)
Valine (GUU)
Alanine (GCU)
Aspartate (GAU)
Glycine (GGU)
Valine (GUC)
Alanine (GCC)
Aspartate (GAC)
Glycine (GGC)
Valine (GUA)
Valine (GUG)
Alanine (GCA)
Alanine (GCG)
Glutamate (GAA)
Glutamate (GAG)
Glycine (GGA)
Glycine (GGG)
Phenylalanine (UUC)
C
C
Second Letter
A
U
C
A
G
U
C
A
G
U
C
A
G
U
C
A
G
The Genetic Code
 Some provide instructions.
 Both UAA and UAG code for STOP, which signals
the end of the gene.
 Multiple codons = same amino acid.
 UUU and UUC both code for Phenylalanine
 If there is a mutation/mistake it might not cause a
problem
The Genetic Code
 All organisms use the same genetic code.
 UUU codes for phenylalanine in redwood trees,
bacteria, and you and me.
 Provides evidence that all life on Earth is
related: every living thing evolved from a
common ancestor instead of multiple
ancestors.
Translation: From mRNA to Protein
 “A communication in a
second language having the
same meaning as the
communication in a first
language”
 Converting a sequence of
nitrogenous bases in mRNA
into a sequence of amino
acids.
Summary
Diagram