Making Proteins

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Making Proteins
DNA

• This image summarizes the processes of
  transcription and translation.
• What are the three stages in this process
  (central dogma) and where are they in this
  picture?

mRNA
rRNA
protein
tRNA
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RNA

• RNA (Ribonucleic Acid)
• Contains Ribose as the sugar in its
  sugar-phosphate backbone
• RNA has Uracil rather than Thymine as a base
• Base pairs A U C G
• 3 types of RNA
• messenger (mRNA)
• transfer (tRNA)
• ribosomal (rRNA)

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Transcription in Prokaryotes

• DNA is transcribed into mRNA

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Translationin Prokaryotes

• mRNA serves as the instructional material to make
  proteins

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Transcriptionin Eukaryotes

• DNA is transcribed into pre-mRNA

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RNA Processingin Eukaryotes

• Non-coding regions of the mRNA, called introns,
  are removed from the pre-mRNA.

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Translationin Eukaryotes

• The mRNA with only the coding region (the exons)
  leaves the nucleus.
• Translation from mRNA to protein occurs in the
  cytoplasm.

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• Steps of DNA Transcription
• Making mRNA from DNA
• Helicase unzips DNA at the gene of interest
• RNA polymerase matches RNA nucleotide bases to
  DNA, using one side as a template.
• 3. The mRNA strand is created. It now
  compliments the original DNA strand (G-C and
  A-U).
• 4. Ligase helps the strand of DNA to close again.
• 5. mRNA strand moves out of nucleus to ribosomes,
  DNA zips up.

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Key Players in Translation

• rRNA RNA that makes up a ribosome
• tRNA RNA that transfers specific amino acids
• mRNA RNA transcribed from DNA
• Codon 3 nucleotides in a row on a strand of
  mRNA that code for an amino acid
• Anticodon 3 nucleotides in tRNA that base pair
  with the codon
• Amino Acids monomers of proteins (20 in humans)

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Steps to TranslationMaking proteins from mRNA

1. Ribosomes attach to the start codon of mRNA
   (AUG), signaling the beginning of the protein
   chain
2. mRNA codons are matched to corresponding tRNA
   anticodons and appropriate amino acids are strung
   together.
3. Dehydration synthesis occurs between the amino
   acids, and they join, making a protein chain with
   peptide bonds in between
4. Ribosomes detach when they come across a stop
   codon (UAA, UAG, UGA). Protein synthesis is
   complete.

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Why do you think RNA uses the triplet code?

• Do the math on your own or with a neighbor.

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CODON BINGO

• Fill in the Bingo Card (on page 45) with the 20
  different amino acids.
• Use your table on page 44 to help
• Watch out for repeated amino acids!
• Wait for your teacher to begin calling out DNA
  letters to begin playing

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Translation Activity

• You and your classmates need to discover the
  hidden protein in your bag.
• Follow the instructions in the bag to unlock the
  mystery protein.

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What if a single base is changed?
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What if a single base is changed?
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What if a single base is changed?