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
• 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
RNApolymerase
Newly made RNA
Direction oftranscription Template
strand of DNA
RNA nucleotides
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
http://ramsey.schoolwires.com/114620810131521263/lib/114620810131521263/Transcription_2.mov
TerminatorDNA
DNA of gene
RNA polymerase
Initiation
PromoterDNA
1
Elongation2
Area shownin Figure 10.9A
Termination3
GrowingRNA
RNApolymerase
CompletedRNA
RNAtranscriptwith capand tail
Exons spliced together
Introns removed
TranscriptionAddition of cap and tail
Tail
DNA
mRNA
Cap
Exon Exon ExonIntron Intron
Coding sequenceNucleus
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• Process of
decoding mRNA into a polypeptide sequence.
Translation
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
tRNAmolecules
Growingpolypeptide
Largesubunit
Smallsubunit
mRNA
tRNA-binding sites
Largesubunit
Smallsubunit
mRNAbinding site
Polypeptide
A site
1 Codon recognitionCodons
Aminoacid
Anticodon
P site
mRNA
Polypeptide
A site
1 Codon recognitionCodons
Aminoacid
Anticodon
P site
mRNA
2 Peptide bondformation
Polypeptide
A site
1 Codon recognitionCodons
Aminoacid
Anticodon
P site
mRNA
2 Peptide bondformation
3 Translocation
Newpeptidebond
Polypeptide
A site
1 Codon recognitionCodons
Aminoacid
Anticodon
P site
mRNA
2 Peptide bondformation
3 Translocation
Newpeptidebond
Stopcodon
mRNAmovement
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:
- occurs in cytoplasm
- mRNA(codon) and tRNA(anticodon)
• Genetic Code is UNIVERSAL!!!!!!!
DNARNAProtein
Proteins
• 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 FunctionAs 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