Protein Synthesis - Biology with Ms. George - Homebiologywithmsgeorge.weebly.com/.../4/3/22439118/protein_synthesis.pdfPROTEIN SYNTHESIS copyright cmassengale. DNA and Genes ... Biology

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PROTEIN SYNTHESIS

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DNA and

Genes

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Roles of RNA and DNA

• DNA is the MASTER PLAN

• RNA is the BLUEPRINT of the

Master Plancopyright cmassengale

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RNA Differs from DNA

• RNA has a sugar ribose

DNA has a sugar deoxyribose


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Other Differences

• RNA contains the base uracil (U)DNA has thymine (T)

• RNA molecule is single-strandedDNA is double-stranded

DNAcopyright cmassengale

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Structure of RNA


Central Dogma of Biology

DNA codes for RNA which guides

the synthesis of proteins!7

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. Three Types of RNA

• Messenger RNA (mRNA) copies DNA’s code & carries the genetic information to the ribosomes

• Ribosomal RNA (rRNA), along with protein, makes up the ribosomes

• Transfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesized


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amino acidattachment site

UA C

anticodon

mRNA

rRNA

tRNA


DNA codes for RNA which guides

the synthesis of proteins!10

Step 1

TRANSCRIPTION IS HAPPENING AT THE SAME TIME AS DNA

REPLICATION!

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Transcription - 1

• A portion of the DNA molecule unzips

• Recall: DNA helicase is the enzyme responsible for this!


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Transcription - 2

• RNA polymerase joins RNA nucleotides using the DNA strand as a template

• This new strand of RNA is the mRNA strand

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Transcription - 3

• After the DNA is transcribed into RNA, editing must be done to the nucleotide chain to make the RNA functional


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Transcription - 3

• Introns, non-functional segments of DNA are snipped out of the chain

• Exons, segments of DNA that code for proteins, are then rejoined by the enzyme ligase


17CAP TailNew Transcript

Result of Transcription


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mRNA Transcript - 4

•mRNA leaves the nucleus through its pores and goes to the ribosomes


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The Genetic Code

• A codon designates an amino acid

• An amino acid may have more than one codon

• There are 20 amino acids, but 64 possible codons

• Some codons tell the ribosome to stop translating


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The Genetic Code

•Use the code by reading from the center to the outside•Example: AUG codes for Methionine


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Name the Amino Acids

• GGG?

• UCA?

• CAU?

• GCA?

• AAA?


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Remember the Complementary Bases

On DNA:A-TC-G

On RNA:A-UC-G


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Question:

What would be the complementary RNA strand for the following DNA sequence?

DNA 5’-GCGTATG-3’


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Answer:

•DNA 5’-GCGTATG-3’

•RNA 3’-CGCAUAC-5’



mRNA creates proteins

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Step 2

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Translation• Translation is the process of decoding the mRNA into a polypeptide chain to create proteins (amino acids)

• Ribosomes read mRNA three bases or 1 codon at a time and construct the proteins


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Transcription

Translation


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Ribosomes

• Composed of rRNA and proteins

• Have two sites for tRNAattachment --- P and A

• The P site is the first to read the mRNA


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Step 1

• mRNA transcriptstart codon AUGmust be read

• This signals to the ribosome to start making proteins

mRNA transcriptcopyright cmassengale

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Ribosomes

P

Site

A

Site

mRNA

A U G C U A C U U C G


Step 2• As ribosome moves, two tRNA with

their amino acids move into site A and P of the ribosome

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32mRNA


2-tRNA

G

aa2

A U

A

1-tRNA

U A C

aa1

anticodon

codoncopyright cmassengale

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1-tRNA 2-tRNA

U A C G

aa1 aa2

A U

A

anticodon

hydroen

bonds codon

peptide bond

3-tRNA

G A A

aa3


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mRNA


1-tRNA

2-tRNA

U A C

G

aa1

aa2

A U

A

peptide bond

3-tRNA

G A A

aa3

Ribosomes move over one codon

(leaves)


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mRNA


2-tRNA

G

aa1

aa2

A U

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U


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mRNA


2-tRNA

G

aa1aa2

A U

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U

(leaves)

Ribosomes move over one codoncopyright cmassengale

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mRNA

G C U A C U U C G

aa1aa2

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U

U G A

5-tRNA

aa5


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mRNA

G C U A C U U C G

aa1

aa2

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U

U G A

5-tRNA

aa5

Ribosomes move over one codoncopyright cmassengale

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mRNA

A C A U G U

aa1

aa2

U

primary

structure

of a protein

aa3

200-tRNA

aa4

U A G

aa5

C U

aa200

aa199

terminator

or stop

codon

Termination


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End Product –The Protein!

• The end products of protein synthesis is an amino acid chain that makes up a protein

aa1

aa2 aa3 aa4aa5

aa200

aa199

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Messenger RNA (mRNA)

methionine glycine serine isoleucine glycine alanine stop

codonprotein

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

start

codon

Amino Acid Chain

aa1 aa2 aa3 aa4 aa5 aa6

peptide bonds

codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1


Beadle & Tatum Hypothesis

• One GENE codes for one POLYPEPTIDE (protein)

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Protein Synthesis - Biology with Ms. George - Homebiologywithmsgeorge.weebly.com/.../4/3/22439118/protein_synthesis.pdfPROTEIN SYNTHESIS copyright cmassengale. DNA and Genes ... Biology