From DNA to Protein

Remember Genes On Chromosomes???

• Some genes contain the instructions to make a protein

Some proteins are:

Structural Functional

Gives form and structure…… Examples:

Keratin (skin, nails, horns), Collagen (connective

tissue), Actin and Myosin (muscles)

Have a job to do…..Examples: Hormones

(signal proteins such as insulin), enzymes,

antibodies

***Proteins are polymers made up of single subunits called amino acids

***Amino acids bonded together (a peptide bond)

From Gene to Protein

• DNA can’t do it alone. Needs the help of another nucleic acid molecule called RNA (Ribonucleic acid)

** RNA involved: tRNA, transfer RNA

mRNA, messenger RNA

Compare DNA and RNA

DNA RNA

A, G, C, T A, G, C, U

*Double-Stranded

*Deoxyribose sugar

*Single-Stranded

*Ribose sugar

How are Proteins Assembled??

• 2 step process make up protein synthesis:– Transcription– Translation

Protein Synthesis Basics

DNA, has the instructions (genetic code) to build a protein

Protein Synthesis is Like a Factory……….

The process by which DNA is ‘read’ to produce a strand of mRNA. Notice

there are NO T’s in mRNA!!!

A G T C G T C A A T G C T A T G C A T T C C G T A C

T C A G C A G T T A C G A T A C G T A A G G C A T GDNA

mRNAA G U C G U C A A U G C U A U G C A U U C C G U A C

RNA polymerase

5’

5’

5’

3’

3’

3’

TRANSCRIPTION

Three mRNA Bases Are Called Codons

** mRNA’s codons code for one of 20 naturally occurring amino acids (See your handout)

** Eample; AUG is amino acid Methionine (Met), the codon that begins translation

**A stop codon (*UAA, UAG or UGA) ends the process

mRNA binds to a ribosome that “reads” the mRNA codons

mRNA codon

When tRNA (transfer RNA) has an anti-codon that compliments mRNA’s codon, it will release its amino acid

Amino Acid

tRNA Anti-Codon

mRNA Codon

A G U C G U C A A U G C U A U G C A U U C C G U A C G

Remember our strand of mRNA from before?

U C A G C A G U U A C G A U A C G U A A G G C A U G C

SER SERALA ALAVAL THR ILE ARG LYS

TRANSLATION

Polypeptides• Proteins are

polypeptides

• They fold according to its function such as enzymes and antibodies

Recall Enzymes proteins that control biochemical reactions including the synthesis of DNA, RNA and Proteins

Let’s Synthesize!

** Remember, to decipher amino acid sequence you read the mRNA codon NOT the tRNA anti-codon

** Look at your table of mRNA codons!

DNA Instruction Code TAC CCG AGC GTA TGC ATT

mRNA’s Transcription AUG GGC UCG CAU ACG

TTC

AAG

GGA

CCU

GTA

CAU UAA

tRNA’s Translation UAC

Amino Acid (based on mRNA!!!)

MetStart

CCG

Gly

AGC

Ser

GUA

His

UGC

Thr

UUC

Lys

GGA

Pro

GUA

His

AUU

Stop

** Notice that tRNA is EXACTLY the same as DNA but the T’s have been replaced with U’s