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. 5-26-1

mRNA

Synthesis ofmRNA in thenucleus

DNA

NUCLEUS

CYTOPLASM

1

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

Types of RNA Involved

• mRNA: Carries info from DNA to ribosome

• 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 Occurs

Here!

Translation Occurs

Here!

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

RULE!

• A on DNA complements U on RNA

• RNA has no T base!

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

Elongation• Transcription progresses at a rate of 40

nucleotides per second in eukaryotes

• 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

How is mRNA Processing Like an Aglet??

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

• RNA splicing: removes introns (noncoding), joins exons (coding)

RNA Processing

Translation

Occurs at Ribosomes• 2 ribosomal subunits (large and small) are made of

proteins and ribosomal RNA (rRNA)

Ribosomes

• Either free floating in cytoplasm

•Or Attached to Rough Endoplasmic Reticulum

Ribosomes

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

Amino Acid Sequences

mRNA and Transcription

Big green thing = RNA polymerase

Protein Synthesis Videos

• NOVA: DNA

Secret of

Life

Prokaryotic Protein Synthesis

Phenotypes are determined through protein synthesis!