Unit 4• Proteins• Transcription (DNA to mRNA)• Translation (mRNA to tRNA to proteins)• Gene expression/regulation (turning genes on and off)• Viruses

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Today’s Exit TicketThe final product of transcription is mRNA. The template used for transcription is DNA. The first step of the process is called initiation

and involves transcription factors binding to the promoter region. This allows RNA polymerase to bind to the DNA and begin

transcribing, in a process called elongation. During that process, the enzyme reads from the 3’ to 5’ direction and builds the new

strand from 5’ to 3’. The last step of transcription is called termination. In eukaryotes, there is another step before translation. This is

called RNA processing and involves removing introns and adding a 5’ cap and 3’ poly-A tail.

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Unit 4• Proteins• Transcription (DNA to mRNA)• Translation (mRNA to tRNA to proteins)• Gene expression/regulation (turning genes on and off)• Viruses

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Today’s Agenda

• Transcription practice• Translation in detail• Mutations

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The template strand of a given gene includes the sequence

3′-G C C A C G T A T C A G-5′.

– What is the sequence of the non-template strand?5’– C G G T G C A T A G T C – 3’

– What is the mRNA sequence made? 5’– C G G U G C A U A G U C – 3’

For each one, be sure to indicate 5′ and 3′ ends.

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The template strand of a given gene includes the sequence

3′-G C C A C G T A T C A G-5′.

What is the amino acid sequence produced from this DNA?

Arg-Cys-Ile-Val

Non-template strand:5’– C G G T G C A T A G T C – 3’

mRNA sequence:5’– C G G U G C A U A G U C – 3’

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Today’s Agenda

•Transcription practice• Translation in detail• Mutations

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Transcription vs. Translation

DNA RNA Proteins

Transcription:• Like copying info from a

book in the reserved section of the library

• Using the same language

Translation:• Literally translating between

two different languages

• Take the copied info from the library and translate it

into French/Spanish/Mandarin

สวั�สดี�ครั�บHello Hullo

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Translation

The major players in translation

U U U UG G G G C

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Translation

Translation:•The structure of tRNA•The ribosome

i. initiateii. elongateiii. terminate

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Translationa) tRNA

For accurate translation, the tRNA HAS to have the right amino acid!

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20 different synthetases 20 different amino acids

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Translationa) tRNA

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3

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Translationa) tRNA

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Translation

Translation:•The structure of tRNA•The ribosome

i. initiateii. elongateiii. terminate

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Translation

a) The ribosome

What is a ribosome?• Made of proteins and

rRNA (ribosomal RNA)

Where are ribosomes?

A. In the nucleusB. Loose in the cytoplasmC. On the Golgi bodyD. On the ERE. More than one of the above is correct

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All those RNA molecules…

• RNA = ribonucleic acid• pre-mRNA = the RNA transcript produced initially

during transcription in eukaryotes• mRNA = messenger RNA = the (processed) RNA

transcript molecule that will actually be translated• tRNA = transfer RNA = the RNA molecule that brings

amino acids to the ribosome• rRNA = ribosomal RNA = RNA that forms the

structure of the ribosome

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Translationb) the ribosome

a) The ribosome

What does it do?

• Serves as the site of matching mRNA codons with tRNA anticodons

• Catalyzes formation of peptide bonds to form proteins

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Translationb) the ribosome

Next amino acidto be added topolypeptide chain

Growing polypeptide

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Translation

Translation:•The structure of tRNA•The ribosome

i. initiateii. elongateiii. terminate

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5. Translation

(i) Initiation of translation

• Small ribosomal subunit binds mRNA.• Scans for start codon (sets reading frame).• Initiator tRNA binds to start codon.

UA G

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Translationb) the ribosome: initiation

Final step of initiation: large ribosomal subunit binds. Final step of initiation: large ribosomal subunit binds.

UA G

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Translation

Translation:•The structure of tRNA•The ribosome

i. initiateii. elongateiii. terminate

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E, P, and A sites• A site: where new aminoacyl tRNAs enter• P site:

– Location of peptidyl tRNA– Where peptide bonds are made

• E site: Exit site

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Elongation

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Also, don’t forgetHank’s crash course on gene expression!

Termination

One more good video:http://www.dnalc.org/resources/3d/16-translation-advanced.html

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USE THE GENETIC CODE TABLE TO TRANSLATE 5 DIFFERENT CODONS into AMINO ACIDS:

RNA:5’ CGC 3’ = ___________5’ UAU 3’ = ___________

NOTE: technically “Codon” refers to the 3 letters in the mRNA that are translated.

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USE THE GENETIC CODE TABLE TO TRANSLATE 5 DIFFERENT CODONS into AMINO ACIDS:

RNA:5’ CGC 3’ = ___ Arg ___5’ UAU 3’ = ___ Tyr ___

NOTE: technically “Codon” refers to the 3 letters in the mRNA that are translated.

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USE THE GENETIC CODE TABLE TO TRANSLATE 5 DIFFERENT CODONS into AMINO ACIDS:

DNA (template strand):3’ TTG 5’ = ___________3’ ACT 5’ = ___________

NOTE: technically “Codon” refers to the 3 letters in the mRNA that are translated.

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USE THE GENETIC CODE TABLE TO TRANSLATE 5 DIFFERENT CODONS into AMINO ACIDS:

DNA (template strand):3’ TTG 5’

RNA 5’ AAC 3’ = Asn

DNA 3’ ACT 5’ RNA 5’ UGA 3’ = Stop

NOTE: technically “Codon” refers to the 3 letters in the mRNA that are translated.

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USE THE GENETIC CODE TABLE TO TRANSLATE 5 DIFFERENT CODONS into AMINO ACIDS:

Brain twister: DNA NON-template strand:5’ ATG 3’ = __________

NOTE: technically “Codon” refers to the 3 letters in the mRNA that are translated.

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USE THE GENETIC CODE TABLE TO TRANSLATE 5 DIFFERENT CODONS into AMINO ACIDS:

Brain twister: DNA NON-template strand:

5’ ATG 3’ = _______DNA template strand =

3’ TAC 5’ = RNA 5’ AUG 3’ = Met (start)

NOTE: technically “Codon” refers to the 3 letters in the mRNA that are translated.

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Mutations in protein coding DNA sequences (exons) can alter protein structure and function in several ways.

How DNA mutations can alter proteinsHow DNA mutations can alter proteins

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5) Mutations in protein coding DNA sequences (exons) can alter protein structure and function in several ways.

a) Substitution - Switching one nucleotide for another

b) Insertion/deletion- Adding or removing a nucleotide can create a frameshift

5) How DNA mutations can alter proteins5) How DNA mutations can alter proteins

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a) Substitution - Switching one nucleotide for another can cause different amino acid to be attached.

5) How DNA mutations can alter proteins5) How DNA mutations can alter proteins

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

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

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a) Substitution- Switching one nucleotide for another can cause NO CHANGE in the protein. How?

5) How DNA mutations can alter proteins5) How DNA mutations can alter proteins

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

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a) Substitution- Switching one nucleotide for another can cause NO CHANGE in the protein. How?

5) How DNA mutations can alter proteins5) How DNA mutations can alter proteins

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

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b) Insertions or Deletions - Inserting an extra nucleotide, or deleting a nucleotide causes a frameshift.

5) How DNA mutations can alter proteins5) How DNA mutations can alter proteins

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

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

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b) Insertions or Deletions - Inserting an extra nucleotide, or deleting a nucleotide causes a frameshift.

5) How DNA mutations can alter proteins5) How DNA mutations can alter proteins

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

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

U

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b) Insertions or Deletions - Inserting an extra nucleotide, or deleting a nucleotide causes a frameshift.

5) How DNA mutations can alter proteins5) How DNA mutations can alter proteins

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c) Gene duplications: a duplicate copy of an exon or whole gene is created in the genome

this is largely how NEW proteins arise in evolution: once a gene has been duplicated, one copy can evolve, while the other one maintains the original function.

5) How DNA mutations can alter proteins5) How DNA mutations can alter proteins

Gene

DNA Exon 1 Exon 2 Exon 3Intron Intron

mRNA Exon 1 Exon 2 Exon 2 Exon 3

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Today’s Exit Ticket

Template DNA __’ C G A G __’

Non-Template __’ T T A A __’

mRNA 5’ A U G A 3’

1) Fill in the blanks in the DNA/RNA chart below.

1) What is the amino acid sequence corresponding to the DNA and RNA sequences below?

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