Transcript Protein Synthesis: Transcription and Translation

What is the job of p53?
What does a cell need to build p53?
Or any other protein?
The central dogma of biology
is…
DNA RNA Protein
What do think this means?
Using the Information Stored in
DNA to Build Proteins
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Genetic code is…
Sequence of bases impt b/c…
A gene is …
Proteins are made on….
How do we get the code for making
proteins out of the nucleus and into the
cytoplasm?
Protein Synthesis: Transcription
and Translation
DNA
vs
RNA
Transcription
• Process by which the genetic code is copied
from DNA into messenger RNA
Transcription occurs in nucleus
before translation
RNA nucleotides
RNA
polymerase
Direction of
transcription
Newly made RNA
Template
strand of DNA
Stages of Transcription
 Initiation: RNA polymerase binds to a promoter,
where the helix unwinds and transcription starts
 Elongation: RNA nucleotides are added to the chain
 Termination: RNA polymerase reaches a terminator
sequence and detaches from the template
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131521263/Transcription_2.mov
RNA polymerase
DNA of gene
Promoter
DNA
Terminator
DNA
1
Initiation
2
Elongation
3
Termination
Completed
RNA
Area shown
in Figure 10.9A
Growing
RNA
RNA
polymerase
Exon Intron
Exon
Intron Exon
DNA
Cap
RNA
transcript
with cap
and tail
Transcription
Addition of cap and tail
Introns removed
Tail
Exons spliced together
mRNA
Coding sequence
Nucleus
Cytoplasm
RNA Splicing
– Eukaryotic mRNA has non-coding sequences called
introns, separating the coding regions called exons
– Eukaryotic mRNA undergoes processing before
leaving the nucleus
– Cap added to 5’ end: single guanine nucleotide
– Tail added to 3’ end: Poly-A tail of 50–250 adenines
– RNA splicing: removal of introns and joining of exons to
produce a continuous coding sequence
Copyright © 2009 Pearson Education, Inc.
10.8 The genetic code is the Rosetta stone of life
– Characteristics of the genetic code
– Triplet: Three nucleotides specify one amino acid
– 61 codons correspond to amino acids
– AUG codes for methionine and signals the start of transcription
– 3 “stop” codons signal the end of translation
Copyright © 2009 Pearson Education, Inc.
Translation
Translation
• Process of
decoding
mRNA into a
polypeptide
sequence.
Codon to Amino Acid
Translation
• Involves:
1. mRNA- carries codon
2. ribosome- rRNA, part
of ribosome
3. tRNA- carries aa and
anticodon
4. enzymes- help aa
bond to tRNA
5. chemical energy, ATP
tRNA
molecules
Growing
polypeptide
Large
subunit
mRNA
Small
subunit
tRNA-binding sites
Large
subunit
mRNA
binding
site
Small
subunit
Amino
acid
Polypeptide
A site
P site
Anticodon
mRNA
Codons
1 Codon recognition
Amino
acid
Polypeptide
A site
P site
Anticodon
mRNA
Codons
1 Codon recognition
2 Peptide bond
formation
Amino
acid
Polypeptide
A site
P site
Anticodon
mRNA
Codons
1 Codon recognition
2 Peptide bond
formation
New
peptide
bond
3 Translocation
Amino
acid
Polypeptide
A site
P site
Anticodon
mRNA
Codons
1 Codon recognition
mRNA
movement
Stop
codon
2 Peptide bond
formation
New
peptide
bond
3 Translocation
Translation: Start
Translation:
Elongation
Translation: Termination
Protein Synthesis
Protein Synthesis: Key Points
• DNA “directs” synthesis of proteins
• Proteins made on ribosomes
• Transcription:
- RNA polymerase unzips DNA
- occurs in nucleus
• Translation:
DNARNAProtein
- occurs in cytoplasm
- mRNA(codon) and tRNA(anticodon)
• Genetic Code is UNIVERSAL!!!!!!!
Proteins
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Composed of aa
Chain of aa called polypeptide
Peptide bonds hold aa together
1 or more polypeptide chains can
link and fold together to form a
3-dimensional protein
• Proteins differ in number and
sequence of aa
• Protein structure determines
their function
Protein Folding and Function
As the amino acid chain grows,
it folds into a three-dimensional
(3-D) structure, which depends
on both the chemical nature
and order of the different amino
acids. The 3-D structure
determines the function of the
protein. When there is a change
in one or more amino acids,
then the ability of the protein to
function may be affected. The
protein's function may be
unchanged or it may become
sluggish, hyperactive, or
inactive.
Proteome: collection of all
proteins in a species