Central Dogma
Big Idea 3: Living systems store, retrieve, transmit, and respond to
info essential to life processes.
Essential Knowledge
• 3A1: DNA, and in some cases RNA, is the primary source of heritable information.
Central Dogma! Protein Synthesis
• Genetic info flows from nucleotide sequence in a
gene to amino acid sequence in a protein
Fig. 5-26-2
mRNA
Synthesis ofmRNA in thenucleus
DNA
NUCLEUS
mRNA
CYTOPLASM
Movement ofmRNA into cytoplasmvia nuclear pore
1
2
Fig. 5-26-3
mRNA
Synthesis ofmRNA in thenucleus
DNA
NUCLEUS
mRNA
CYTOPLASM
Movement ofmRNA into cytoplasmvia nuclear pore
Ribosome
AminoacidsPolypeptide
Synthesisof protein
1
2
3
• tRNA: Bind specific amino acids and allow info in the mRNA to be translated into a linear
peptide sequence.
Types of RNA Involved
What’s a Pirates
Favorite RNA??
• Functional building blocks of ribosomes (site of translation)
rRNA!
• RNAi: RNA interference molecu
les stops gene expression; may destroy mRNA.
• MicroRNA and siRNA (small
interfering RNA) that regulate gene
expression.
Types of RNA Involved
Transcription• DNA mRNA,
made by RNA polymerase II
• RNA polymerase binds on promoter (nucleotide), reads DNA from 3’ to 5’
• 3 stages: Initiation,Elongation,
Termination
Initiation• Promoters: start RNA synthesis, TATA box
is one in eukaryotes
• Transcription factors: help binding of RNA polymerase
• Assembly called transcription initiation complex
Fig. 17-8
A eukaryotic promoterincludes a TATA box
3
1
2
3
Promoter
TATA box Start point
Template
TemplateDNA strand
535
Transcriptionfactors
Several transcription factors mustbind to the DNA before RNApolymerase II can do so.
5533
Additional transcription factors bind tothe DNA along with RNA polymerase II,forming the transcription initiation complex.
RNA polymerase II
Transcription factors
55 53
3
RNA transcript
Transcription initiation complex
• In bacteria: polymerase stops transcription at end of terminator (nucleotide sequence)
• In eukaryotes: polymerase continues transcription after pre-mRNA is cut polymerase eventually
falls off DNA
Termination
RNA ProcessingEnzymes add a Poly A Tail on 3’ end and a
GTP Cap on 5’ end
• Helps export mRNA and protect from degrading hydrolytic enzymes
Occurs at Ribosomes• 2 ribosomal subunits (large and small) are made of
proteins and ribosomal RNA (rRNA)
P Site: holds tRNA that carries growing polypeptide chain
A Site: holds next tRNA that will add a. acid to chain
E Site: holds exit tRNA that doesn’t have an a. acid
Ribosomes
Initiation of Translation• mRNA interacts w/ rRNA of ribosome at start codon
AUG
• mRNA is read in triplets called codons, which encodes a specific amino acid.
• tRNA carries the amino acid to the mRNA and ribosome
• Amino acids join to make a peptide chain• Stop codon stops process, release new peptide
chain.
Termination of Translation