Protein Synthesis
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Protein Synthesis. Unit Objectives (Chapter 12-3). By the end of this unit you will: know what transcription is know what translation is understand how proteins are made. Transcription. Transcribing or copying the coded message of DNA onto a single stranded nucleic acid called mRNA

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Unit objectives chapter 12 3
Unit Objectives (Chapter 12-3)

By the end of this unit you will:

  • know what transcription is

  • know what translation is

  • understand how proteins are made.


Transcription
Transcription

  • Transcribing or copying the coded message of DNA onto a single stranded nucleic acid called mRNA

  • DNA’s code is contained in groups of 3 nitrogen bases called DNA triplets

  • One side of DNA is considered the coding side, or template, and the other side is considered the complimentary side.

  • Left side – coding side

  • Right side – complimentary strand


  • To begin transcription, Helicase causes the molecule to split or “unzip”.

  • This exposes the nitrogen bases of the coding side

  • Free floating mRNA nucleotides attach to the coding side of DNA

  • The whole mRNA strand is removed from the coding side of DNA

  • The mRNA strand then moves out of the nucleus and heads for a ribosome.

  • The DNA strand then can re-attach with the complementary side of DNA


Transcription1
Transcription split or “unzip”.

Transcription and the TATA's


mRNA split or “unzip”.

  • Each group of 3 nitrogen bases of mRNA are called codons.


Codon wheel
Codon Wheel split or “unzip”.


Here is how we will do it
Here is how we will “do it”! split or “unzip”.

  • DNA Coding Triplet:

  • ATA CGA

  • mRNA Codons that would be transcribed:

  • UAU GCU

  • Amino Acids:

    Tyrosine + Alanine


Summary
Summary split or “unzip”.

  • Transcription is copying the DNA code onto a mRNA molecule.

  • mRNA leaves the nucleus and moves to the ribosome where the message is translated

  • AUG is called the “Initiation Codon” . It begins the process and always codes for Methionine

  • “Termination Codons” indicate the end of the process. UAG,UAA, and UGA are termination codons and don’t code for any amino acids


Let s try transcription
Let’s try Transcription: split or “unzip”.

  • Assume the sequence of nitrogen bases below represents the coding side of DNA.

  • ACT CCC CGA TAC

  • Transcribe the DNA triplets into mRNA codons

  • Draw the mRNA molecule that would be produced during Transcription.

  • Translate the mRNA molecule into the amino acids it represents. Use your codon wheel.


Look like this
Look like this? split or “unzip”.


Transcription review
Transcription Review split or “unzip”.

  • DNA contains the genetic code for the production of __________.

  • Each group of 3 nitrogen bases in DNA is called a __________.

  • The genetic code of _____ is trapped inside the nucleus because it is ____________ to fit through the pores in the nuclear envelope.

  • __________ is the process of copying the genetic code of _____ onto a single strand of _____.

  • The single stranded _____ molecule falls on it’s side with it’s nitrogen bases pointing _____ and moves out of the nucleus to find a __________.

  • Each group of 3 nitrogen bases in mRNA is called a __________.

  • AUG is a special codon that is called an ________________. It always codes for the amino acid __________.

  • Check you codon wheel and identify the amino acids that the following codons code for:

    • GGC - __________

    • UUU - __________

    • CAU - __________

    • GUA - __________


Transcription review1
Transcription Review split or “unzip”.

  • Another special codon found in mRNA stops the chain of amino acids and indicates the protein is complete. These codons are called ________________. There are only 3 of the codons: _______; ________ and _______.

  • We are always going to assume that the coding side of DNA will be the __________ side.

  • Opposite the coding side is called the __________ side.

  • Two enzymes play a role in transcription: ____________ unzips the DNA molecule and __________________ helps attach the free-floating mRNA nucleotides to the coding side of DNA.


Transcription review2
Transcription Review split or “unzip”.

  • DNA contains the genetic code for the production of Protein.

  • Each group of 3 nitrogen bases in DNA is called a DNA triplet.

  • The genetic code of DNA is trapped inside the nucleus because it is too big to fit through the pores in the nuclear envelope.

  • Transcription is the process of copying the genetic code of DNA onto a single strand of mRNA.

  • The single stranded mRNA molecule falls on it’s side with it’s nitrogen bases pointing up and moves out of the nucleus to find a ribosome.

  • Each group of 3 nitrogen bases in mRNA is called a codon.

  • AUG is a special codon that is called an Initiation codon. It always codes for the amino acid Methionine.

  • Check you codon wheel and identify the amino acids that the following codons code for:

    • GGC - Glycine

    • UUU - Phenylalanine

    • CAU - Histidine

    • GUA - Valine


Transcription review3
Transcription Review split or “unzip”.

  • Another special codon found in mRNA stops the chain of amino acids and indicates the protein is complete. These codons are called Termination codons. There are only 3 of the codons: UGA; UAA and UAG.

  • We are always going to assume that the coding side of DNA will be the left side.

  • Opposite the coding side is called the complimentary side.

  • Two enzymes play a role in transcription: Helicase unzips the DNA molecule and RNA polymerase helps attach the free-floating mRNA nucleotides to the coding side of DNA.


Translation
Translation split or “unzip”.

  • The process where the message of mRNA is translated into sequences of amino acids.

  • Translation happens on the surface of ribosomes.

  • 3 codons can fit on the ribosome at one time.

  • Remember tRNA?


tRNA split or “unzip”.

 amino acid (specific to tRNA)

 tRNA molecule

 nitrogen bases called anticodons

Serine


Trna cont
tRNA cont… split or “unzip”.

  • Each tRNA molecule with one specific anticodon sequence can carry only one specific amino acid.

  • If the anticodon of tRNA is complimentary to the codon of mRNA the amino acid carried by that tRNA is dropped off.

  • Protein Synthesis PH

  • Let’s go back to our mRNA molecule. Draw the respective tRNA molecules that would be involved in Translation.


Translation animations
Translation Animations split or “unzip”.

  • Translation

  • Translation 2

  • Translation 3


Activity
Activity split or “unzip”.

  • Use your codon chart to complete the following table:


A few things we need to know
A few things we need to know… split or “unzip”.

  • Gene A

  • Gene B

  • Exons – translatable segments of a chromosome

  • Introns – segments of DNA that do NOT code for proteins

    • Nonsense DNA

  • AUG – intiation codon

  • Codes for methionine

  • UAA, UAG, and UGA are all termination codons


Ribosome structure
Ribosome Structure split or “unzip”.

  • “A” Site

  • Arrival Site

  • First tRNA arrives

  • “P” Site

  • Peptidyl Site

  • Amino Acids bond together

  • “E” Site

  • Exit site

  • Naked tRNA goes to find another amino acid

“A” Site

“P”

Site

“E” Site


Protein synthesis
Protein Synthesis split or “unzip”.


Protein synthesis1
Protein Synthesis split or “unzip”.

  • Another look at Protein Synthesis


Quiz protein synthesis
Quiz: Protein Synthesis split or “unzip”.

  • Assume the strand of DNA nucleotides below represents the coding side .

  • ACT CCA CGA TAC

  • Draw the mRNA molecule that would be transcribed.(Value: 4)

  • Draw the three tRNA molecules that would be complimentary to the mRNA molecule you created. Make sure the appropriate amino acid and anti-codon are positioned on the tRNA drawings. (Value: 3)

  • Using you amino acid chart, draw the polypeptide that would be created. (Value:3)


Mutations
Mutations split or “unzip”.

  • Point Mutation: A change in one nitrogen base in DNA.

  • EX: DNA AAA TCT CGA

  • mRNAUUU AGA GCU

  • Amino AcidsPhen-Arg-Ala

  • Point Mutation

  • DNA AAA TGT CGA

  • mRNA UUU ACA GCU

  • Amino AcidsPhen-Thre- Ala


Lucky point mutation
``Lucky`` Point Mutation split or “unzip”.

  • DNAAAA TCT CGA

  • mRNA UUU AGA GCU

  • A.A. Phen-Arg-Ala

  • DNA AAA TCC CGA

  • mRNAUUU AGG GCU

  • A.A.Phen – Arg - Ala


Frame shift mutations
Frame shift Mutations split or “unzip”.

  • - Mutation that deletes or adds a nitrogen base pair.

  • - The result impacts the rest of the amino acids in the chain

  • DNA AAA TCT CGA

  • mRNA UUU AGA GCU

  • A.A. Phen – Arg- Ala

  • (Deletion) AA ATC TCG_

  • mRNA

  • A.A. YIKES!


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