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Protein Synthesis

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. Big picture. DNA contains the genetic code which controls the production of proteins

xandra-riley
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Protein Synthesis

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  1. Protein Synthesis

  2. 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.

  3. Big picture • DNA contains the genetic code which controls the production of proteins • Proteins, as we have learned, do everything! • There are two important events which must happen in order to make a protein; transcription and translation

  4. 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

  5. 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

  6. Transcription Transcription and the TATA's

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

  8. Codon Wheel

  9. The Genetic Code • Use the code by reading from the center to the outside • Example: AUG codes for Methionine

  10. Name the Amino Acids • GGG? • UCA? • CAU? • GCA? • AAA?

  11. Our “way”:

  12. Summary • 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

  13. Let’s try Transcription: • Draw a DNA molecule with the base sequence ATG GCA. Make the 5’ on the top left. • Assuming the coding side of DNA is the left side, transcribe a mRNA molecule. Draw the molecule horizontally. “Remember how we do it!”

  14. Look like this?

  15. Transcription Review • 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 - __________

  16. Transcription Review • 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.

  17. Transcription Review • 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

  18. Transcription Review • 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.

  19. Translation • 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?

  20. tRNA  amino acid (specific to tRNA)  tRNA molecule  nitrogen bases called anticodons Serine

  21. tRNA cont… • 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

  22. Translation Animations • Translation • Translation 2 • Translation 3

  23. Activity • Use your codon chart to complete the following table:

  24. A few things we need to know… • Gene A • Gene B • Exons – translatable seqments 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

  25. Protein Synthesis

  26. Protein Synthesis • Another look at Protein Synthesis

  27. Activity: Protein Synthesis • Assume the strand of DNA nucleotides below represents the coding side (The Wife!) • ACT CCA CGA TAC • Transcribe a mRNA molecule using the coding side. Detach it and draw it hortizontally. • 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. • Using you amino acid chart, draw the reactants and products of this synthesis.

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