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Chapter 12: Protein Synthesis What is DNA?. Chapter 13 Protein Synthesis - Overview. The DNA of the gene is transcribed into RNA Which is translated into protein The flow of genetic information from DNA to RNA to Protein is called the CENTRAL DOGMA. DNA. Transcription. RNA.

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slide2
Chapter 13 Protein Synthesis - Overview

The DNA of the gene is transcribed into RNA

Which is translated into protein

The flow of genetic information from DNA to RNA to Protein is called the CENTRAL DOGMA

DNA

Transcription

RNA

Translation

Protein

slide3
Chapter 12 Protein Synthesis (Overview)

Central Dogma - FLOW IS FROM DNA TO RNA TO PROTEIN

flow is from dna to rna to protein
FLOW IS FROM DNA TO RNA TO PROTEIN

Genes on DNA are expressed through proteins, which provide the molecular basis for inherited traits

A particular gene, is a linear sequence of many nucleotides

Specifies a polypeptide (long protein made of amino acids)

Chapter 13 Protein Synthesis (Overview)

slide5
Chapter 12 Protein Synthesis (Overview)

Genes - discrete units of hereditary information comprised of a nucleotide sequence found in a DNA molecule.

12 1 rna
12.1 RNA

Three Types of RNA

Messenger RNA (mRNA) – carries copies of genes (DNA) to the rest of the cell.

Ribosomal RNA (rRNA) – make up the ribosomes.

Transfer RNA (tRNA) – transfers the amino acids to the ribosomes as specified by the mRNA

12 1 messenger mrna
12-1 Messenger (mRNA)

Three main differences between mRNA and DNA

Ribose instead of deoxyribose

mRNA is single stranded

mRNA has uracil in place of thymine (U instead of T)

slide8
12.1TRANSCRIPTION: The process of making mRNA from DNA

Why do you need this process?

Location of DNA? Nucleus

Location of Ribosome? Cytoplasm

mRNA takes code from DNA in the nucleus to the cytoplasm

T

A

C

T

T

C

A

A

A

A

T

C

A

T

G

A

A

G

T

T

T

T

A

G

Strand to be transcribed

DNA

Transcription

G

U

U

U

A

G

A

U

A

A

G

U

RNA

Startcondon

Stopcondon

Translation

Met

Polypeptide

Lys

Phe

slide9
Transcription produces genetic messages in the form of mRNA

12.1 In the nucleus, the DNA helix unzips

And RNA polymerase lines up nucleotides along one strand of the DNA, following the base pairing rules

As the single-stranded messenger RNA (mRNA) peels away from the gene

The DNA strands rejoin

RNA nucleotides

RNA

polymerase

A

C

C

A

T

T

A

U

T

C

T

G

U

G

A

C

A

U

C

C

A

C

C

A

G

A

T

T

T

A

G

G

Direction of

transcription

Template

Strand of DNA

Newly made RNA

slide10
12.1 Eukaryotic mRNA is processed before leaving the nucleus

Noncoding segments called introns are spliced out leaving only the coding exons

A 5’ cap and a poly A tail are added to the ends of mRNA

Cap and tail protect mRNA

Exon Intron Exon Intron Exon

DNA

Transcription

Addition of cap and tail

Cap

RNA

transcript

with cap

and tail

Introns removed

Tail

Exons spliced together

mRNA

Coding sequence

Nucleus

Cytoplasm

5’

3’

slide11
A

C

C

A

T

T

A

U

T

C

G

T

U

G

A

C

A

U

C

C

A

C

C

A

G

A

T

T

T

A

G

G

Direction of

transcription

12 3 protein synthesis translation
12-3 Protein Synthesis - Translation
  • Translation is defined as going from mRNA to protein
    • tRNA which have amino acids attached are going to the ribosome in the cytoplasm.
      • What are amino acids? monomers of proteins
      • Does the order of amino acids matter? Yes, they must be in order for the protein to fold correctly.

Amino acid

attachment site

slide14
How does the correct tRNA (with amino acid attached) bind to the mRNA? The tRNA contains an anticodon which matches up with the mRNA sequence (codon).

Transfer RNA (tRNA) molecules serve as interpreters during translation

0

Amino acid

attachment site

Amino acid attachment site

Hydrogen bond

RNA polynucleotide chain

Anticodon

Anticodon

slide15
Ribosomes build polypeptides (proteins)

A ribosome consists of two subunits

Each made up of proteins and a kind of RNA called ribosomal RNA

Translation at Ribosome

tRNAmolecules

Growingpolypeptide

Largesubunit

mRNA

Small

subunit

12.3 Translation

slide16
The subunits of a ribosome

Hold the tRNA and mRNA close together during translation

12.3 Translation

Large ribosomalsubunit

Met

Met

Initiator tRNA

P site

A site

U

C

U

A

C

A

A U G

AUG

Startcodon

Small ribosomalsubunit

mRNA

1

2

slide17
Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation

Once initiation is complete amino acids are added one by one to the first amino acid

The mRNA moves a codon at a time

A tRNA with a complementary anticodon pairs with each codon, adding its amino acid to the peptide chain

slide18
Figure out the exact sequence of amino acids needed
  • Take the DNA and transcribe it into mRNA
      • Example: TAC ATA CTA GCG ACT
      • mRNA:
  • Take the mRNA sequence and decode it using the codon chart.

AUG

UAU

GAU

CGC

UGA

AUG = MET

UAU = TYR

GAU = ASP

CGC = ARG

Animation

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