Learning Objectives1. Explain how the code of DNA

transcribed into messenger RNA.

2. Explain how messenger RNA is translated into a protein.

3. Describe how to make a protein beginning with a gene.

Bodies are made up of cells

All cells run on a set of instructions spelled out in DNA

Bodies → Cells → DNA

How does DNA code for cells & bodies? how are cells and bodies made from the

instructions in DNA?

DNA → Cells → Bodies

DNA has the information to build proteins genes

DNA → Proteins → Cells → Bodies

proteinscells

bodiesDNA gets all the glory,Proteins do all the work

How do proteins do all the work?

– Proteins run living organisms

– Enzymes control all chemical reactions in living organisms

– Structure

• all living organisms are built out of proteins

cytoplasm

nucleus

Cell organization– DNA is in the nucleus

• genes = instructions for making proteins

– want to keep it there = protected• “locked in the vault”

Cell organization

• Proteins– chains of amino acids– made by a “protein factory” in

cytoplasm = ribosome

nucleus

cytoplasm

ribosome

buildproteins

Passing on DNA information

• Need to get DNA gene information from nucleus to cytoplasm– need a copy of DNA– messenger RNA (mRNA) does this

nucleus

cytoplasm

ribosomemRNA

buildproteins

DNA vs. RNA

DNA• deoxyribose sugar • nitrogen bases

– G, C, A, T– T : A– C : G

• double stranded

RNA• ribose sugar • nitrogen bases

– G, C, A, U– U : A– C : G

• single stranded

mRNA

From nucleus to cytoplasm

DNA

transcription

nucleus

cytoplasm

translation

trait

protein

Transcription

• Making mRNA from DNA

• DNA strand is the template (pattern)– match bases

• U : A

• G : C

• Enzyme– RNA polymerase

Matching bases of DNA & RNA

• Double stranded DNA unzips

A G GGGGGT T A C A C T T T T TC C C CA A

Matching bases of DNA & RNA

• Double stranded DNA unzips

A G GGGGGT T A C A C T T T T TC C C CA A

Matching bases of DNA & RNA

• Match RNA bases to DNA bases on one of the DNA strands

U

A G GGGGGT T A C A C T T T T TC C C CA A

U

UU

U

U

G

G

A

A

A C CRNA

polymerase

C

C

C

C

C

G

G

G

G

A

A

A

AA

Matching bases of DNA & RNA

• U instead of T is matched to A

TACGCACATTTACGTACGCGGDNA

AUGCGUGUAAAUGCAUGCGCCmRNA

How does mRNA code for proteins?

• mRNA leaves nucleus

• mRNA goes to ribosomes in cytoplasm

• Proteins built from instructions on mRNA

aa aa aa aa aa aa aa aa

How?

mRNA

U C CCCCCA A U G U G A A A A AG G G GU U

How does mRNA code for proteins?

How can you code for 20 amino acids withonly 4 DNA bases (A,U,G,C)?

TACGCACATTTACGTACGCGGDNA

AUGCGUGUAAAUGCAUGCGCCmRNA

Met Arg Val Asn Ala Cys Alaprotein

?

ribosome

aa aa aa aa aa aa aa aa

AUGCGUGUAAAUGCAUGCGCCmRNA

mRNA codes for proteins in triplets

TACGCACATTTACGTACGCGGDNA

AUGCGUGUAAAUGCAUGCGCCmRNA

Met Arg Val Asn Ala Cys Alaprotein

?

Codon = block of 3 mRNA bases

codon

ribosome

The mRNA code• For ALL life!

– strongest support for a common origin for all life

• Code has duplicates– several codons for each

amino acid– mutation insurance!

Start codon AUG methionine

Stop codons UGA, UAA, UAG

How are the codons matched to amino acids?

TACGCACATTTACGTACGCGGDNA

AUGCGUGUAAAUGCAUGCGCCmRNA

anti-codon

codon

tRNAUAC

MetGCA

ArgCAU

Val Anti-codon = block of 3 tRNA bases

aminoacid

mRNA to protein = Translation

• The working instructions → mRNA• The reader → ribosome• The transporter → transfer RNA (tRNA)

mRNAU C CCCCCA A U G U G A A A A AG G G GU U

aaaa

aa

tRNA

GGU

aa

tRNA

U A C

aa

tRNA

GA C

tRNA

aa

A GU

ribosome

aa

aa

aaaa

aa

aa

aa

mRNA

From gene to protein

DNA

transcription

nucleus

cytoplasm

protein

translation

trait

U C CCCCCA A U G U G A A A A AG G G GU Uribosome

tRNA

aa

transcription

cytoplasm

nucleus

translation

trait

protein

From gene to protein

transcriptiontranscription

translationtranslation

proteinprotein

Whoops!See what happens when

your genes don’t work right!

Any Questions??