ObjectivesObjectives

► I know what a gene isI know what a gene is► I can describe the process of protein I can describe the process of protein

synthesissynthesis► I can describe the functions of the I can describe the functions of the

three types of RNAthree types of RNA► I can predict the protein that will be I can predict the protein that will be

made from a strand of DNAmade from a strand of DNA

Protein Protein StructureStructure

GENESGENES

DNA -BLUEPRINTS

NUCLEUS

RIBOSOMES

CYTOPLASM MAKES PROTEINS

HOW IS DNA GOING TO TELL THE RIBOSOMES WHAT TO

MAKE?

DNA HAS TO SEND A MESSAGE

Protein SynthesisProtein Synthesis

AA AA AAAA

TRANSCRIPTION TRANSLATION

DNA mRNA PROTEIN

“WRITE THEMESSAGE”

“DECODE THEMESSAGE”

NUCLEUS

RIBOSOMESCYTOPLASM

DNA REPLICATION&

TRANSCRIPTIONTRANSCRIPTION

TRANSLATION

AA

AA

AA

AA

RNA – THE MESSAGERNA – THE MESSAGE

U

C

G

U

A

DNADNA

A

C

A

C

A T

T

G

T

G

RNAU

C

A

U

G

D R

RNARNAA.A. RRiboibonnucleic ucleic AAcidcid

i.i. Single strandedSingle stranded

ii.ii. Has ribose sugarHas ribose sugar

iii.iii. Has Has UUracil instead of racil instead of TThyminehymine

B.B. Bonding PatternBonding Pattern

i.i. A - UA - U

ii.ii. C - GC - G

3 types of RNA3 types of RNA

i.i. mRNAmRNA – messenger RNA – – messenger RNA – carries DNA “message” from the carries DNA “message” from the nucleus to the rest of the cellnucleus to the rest of the cell

ii.ii. tRNAtRNA – transfer RNA – brings or – transfer RNA – brings or “transfers” amino acids from “transfers” amino acids from the cytoplasm to the ribosomes the cytoplasm to the ribosomes to assemble proteinsto assemble proteins

iii.iii.rRNArRNA – ribosomal RNA – helps – ribosomal RNA – helps make up ribosomesmake up ribosomes

Making Proteins: 2 stepsMaking Proteins: 2 steps

1.1. TranscriptionTranscription = re-writing the = re-writing the instructions from the language of DNA instructions from the language of DNA to the language of RNAto the language of RNA

WHY? Because DNA is too large to leave WHY? Because DNA is too large to leave the nucleus, but mRNA can slip out the nucleus, but mRNA can slip out through the nuclear poresthrough the nuclear pores

2.2. TranslationTranslation = de-coding the message = de-coding the message (mRNA CODES for Amino Acids)(mRNA CODES for Amino Acids)

Transcription – making of mRNATranscription – making of mRNA

A.A. Copy part of DNA into complementary Copy part of DNA into complementary RNA strand “RNA strand “Writing of RNA using DNAWriting of RNA using DNA””

B.B. RNA polymerase RNA polymerase – enzyme that binds – enzyme that binds to DNA to use as template and to DNA to use as template and assemble RNA nucleotidesassemble RNA nucleotides

i.i. Binds to region of DNA called the Binds to region of DNA called the ‘‘promoterpromoter’ which tells the enzyme where to ’ which tells the enzyme where to startstart

ii.ii. RNA polymerase releases DNA strand when RNA polymerase releases DNA strand when RNA strand is completeRNA strand is complete

C.C. mRNA will then travel into cytoplasmmRNA will then travel into cytoplasm

G

C

A

T

A U

C

A

U

G

DNA is TRANSCRIBED into DNA is TRANSCRIBED into mRNAmRNA

D

D

D

D

D

R

R

R

R

R

Transcribe this DNA Transcribe this DNA sequencesequence

►CATGACTAGCATGACTAG►GUACUGAUCGUACUGAUC

Protein SynthesisProtein Synthesis

AA AA AAAA

TRANSCRIPTION TRANSLATION

DNA mRNA PROTEIN

“WRITE THEMESSAGE”

“DECODE THEMESSAGE”

NUCLEUS

RIBOSOMESCYTOPLASM

DNA REPLICATION&

TRANSCRIPTIONTRANSCRIPTION

TRANSLATION

AA

AA

AA

AA

TRANSLATIONTRANSLATIONA.A. The process of translating or The process of translating or

decoding the DNA message (mRNA) decoding the DNA message (mRNA) into amino acid chains (proteins)into amino acid chains (proteins)

B.B. tRNAtRNAi.i. tRNA have 3 bases on them called an tRNA have 3 bases on them called an

anticodonanticodon which pairs with the codon of which pairs with the codon of the mRNAthe mRNA

ii.ii. Each tRNA adds one amino acid that it Each tRNA adds one amino acid that it has brought from the cytoplasm making has brought from the cytoplasm making the protein chain longerthe protein chain longer

tRNA – cloverleaf shapetRNA – cloverleaf shape

U G C

ANTICODON

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

CODON

AA

U A C

AA

G U A

AA

A U G

AA

A C UtRNA

RIBOSOMES

Steps of Protein SynthesisSteps of Protein Synthesis1.1. mRNA leaves nucleus and attaches to mRNA leaves nucleus and attaches to

ribosomesribosomes

2.2. tRNA with the anticodon UAC attaches tRNA with the anticodon UAC attaches to the mRNA start codon to the mRNA start codon AUGAUG to begin to begin protein chain with amino acid protein chain with amino acid methioninemethionine

3.3. Additional tRNA’s add other amino Additional tRNA’s add other amino acids to the protein chain connecting acids to the protein chain connecting them with them with peptide bondspeptide bonds

4.4. Protein synthesis continues until it Protein synthesis continues until it reaches a reaches a stop codonstop codon (UGA, UAA, UAG) (UGA, UAA, UAG)

Genetic CodeGenetic Code

A.A. Proteins are built from different Proteins are built from different combinations of 20 amino acidscombinations of 20 amino acids

B.B. AA sequence is determined by AA sequence is determined by sequence of bases in mRNAsequence of bases in mRNA

C.C. Each 3 base codon “codes” for a Each 3 base codon “codes” for a different amino aciddifferent amino acid

D.D. 64 possible codons64 possible codonsA.A. 61 code for 20 amino acids61 code for 20 amino acids

B.B. 3 are “Stop” codons3 are “Stop” codons

How do we know what Amino How do we know what Amino Acid to add?Acid to add?

USE THE mRNACODE TO TRANSLATEINTO AMINO ACID’S

mRNA – 1) AUG2) CAU3) UAC4) UGA

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

CODON

MET

U A C A C UtRNA

RIBOSOMES

HIS

G U A

METTYR

A U G

HISMET

TYR

HISMET

PRACTICEPRACTICE

►DNA : T A C G A C G T A A A A A C TDNA : T A C G A C G T A A A A A C T

►mRNA: ?mRNA: ?

►tRNA: ?tRNA: ?

►Amino Acid Sequence: ?Amino Acid Sequence: ?

PRACTICEPRACTICE

►DNA : T A C - G A C - G T A - A A A - A C DNA : T A C - G A C - G T A - A A A - A C TT

►mRNA: A U G - C U G - C A U - U U U - U G mRNA: A U G - C U G - C A U - U U U - U G AA

►tRNA: U A C - G A C - G U A - A A A - A C tRNA: U A C - G A C - G U A - A A A - A C UU

►AA Seq: MET - LEU - HIS - PHE AA Seq: MET - LEU - HIS - PHE

DNA ReplicationDNA Replication

A

C

A

C

A T

T

G

T

G

G

C

A

T

A U

C

A

U

G

DNA DNA TRANSCRIPTIONTRANSCRIPTION

D

D

D

D

D

R

R

R

R

R

DNA mRNA

NUCLEUS

RIBOSOMES

CYTOPLASM

DNA REPLICATION&

TRANSCRIPTIONTRANSCRIPTION

TRANSLATION

AAAA

AAAA

PRACTICEPRACTICE

►DNA :DNA : TAT – CGC – TAT – CGC – AGCAGC

►mRNA: mRNA: AUA – GCG - UCGAUA – GCG - UCG►Amino Acid Sequence:Amino Acid Sequence:Ile - Ile - Ala - Ser Ala - Ser