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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. 1. Today’s Exit Ticket.

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Presentation Transcript
slide1

Unit 4

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

1

slide2

Today’s Exit Ticket

The 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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slide3

Unit 4

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

3

slide4

Today’s Agenda

  • Transcription practice
  • Translation in detail
  • Mutations

4

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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′.

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’

What is the amino acid sequence produced from this DNA?

Arg-Cys-Ile-Val

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slide7

Today’s Agenda

  • Transcription practice
  • Translation in detail
  • Mutations

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slide8

Transcription vs. Translation

DNA RNA Proteins

Hello

สวัสดีครับ

Hullo

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

8

slide9

Translation

U

U

U

G

U

G

C

G

G

The major players in translation

9

slide10

Translation

Translation:

  • The structure of tRNA
  • The ribosome
    • initiate
    • elongate
    • terminate

10

slide12

Translation

a) tRNA

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

1

20 different synthetases  20 different amino acids

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slide13

Translation

a) tRNA

2

3

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Translation

a) tRNA

4

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Translation

Translation:

  • The structure of tRNA
  • The ribosome
    • initiate
    • elongate
    • terminate

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Translation

  • The ribosome
  • What is a ribosome?
    • Made of proteins and

rRNA (ribosomal RNA)

  • Where are ribosomes?
    • In the nucleus
    • Loose in the cytoplasm
    • On the Golgi body
    • On the ER
    • 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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Translation

b) the ribosome

  • 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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Translation

b) the ribosome

Growing polypeptide

Next amino acid

to be added to

polypeptide chain

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slide20

Translation

Translation:

  • The structure of tRNA
  • The ribosome
    • initiate
    • elongate
    • terminate

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5. Translation

A

G

U

(i) Initiation of translation

  • Small ribosomal

subunit binds

mRNA.

  • Scans for start

codon (sets reading

frame).

  • Initiator tRNA binds

to start codon.

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Translation

A

G

U

b) the ribosome: initiation

 Final step of initiation: large ribosomal subunit binds.

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slide23

Translation

Translation:

  • The structure of tRNA
  • The ribosome
    • initiate
    • elongate
    • 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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Termination

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

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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slide29

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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slide30

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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slide31

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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slide32

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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slide33

How DNA mutations can alter proteins

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

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Fanpop.com

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5) How DNA mutations can alter proteins

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

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5) 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

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

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5) How DNA mutations can alter proteins

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

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

36

slide37

5) How DNA mutations can alter proteins

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

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

37

slide38

5) 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

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

38

slide39

5) 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 G G C U A A

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

U

39

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5) How DNA mutations can alter proteins

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

40

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5) How DNA mutations can alter proteins

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.

Gene

DNA

Exon 1

Intron

Exon 2

Intron

Exon 3

Exon 3

Exon 1

Exon 2

Exon 2

mRNA

41

slide42

Today’s Exit Ticket

  • Fill in the blanks in the DNA/RNA chart below.
  • What is the amino acid sequence corresponding to the DNA and RNA sequences below?

42