Building Proteins

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Building Proteins

• From RNA to protein molecules
• 12-3

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By the end of this lesson, you should be able to

1. Tell how DNA differs from RNA
2. Compare the 3 types of RNA
3. Describe the process of transcription
4. Describe the process of translation
5. Explain the relationship between genes and
   proteins
6. Explain how a mutation occurs

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How does the information on the DNA get used by
the cell?

• Proteins NEED to be made!!!
• By who?
• How does the information get there?

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Genes sections of DNA that code for a protein
ONE Gene ? RNA ? ONE Protein
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Types of RNA

1. Messenger RNA (mRNA)
2. Ribosomal RNA (rRNA)
3. Transfer RNA (tRNA)

rRNA
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Types of RNA

• Messenger RNA (mRNA)- carry instructions on the
  DNA to the ribosome
• Ribosomal RNA (rRNA)-make-up the ribosome
• Transfer RNA (tRNA)-carries the correct amino
  acid to the ribosome to build proteins

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How is it different from DNA?

• Carries out the cells instructions instead of
• Is single stranded instead of
• Contains the sugar ribose instead of
• Contains the nitrogenous base Uracil that binds
  to adenine instead of.

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Process of Transcription

• 1) RNA polymerase binds to the promoter region on
  the DNA
• Promoters nucleotide sequence that signals the
  RNA polymerase to bind to them
• 2) RNA polymerase separates the DNA strands

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Process of Transcription

• 3) Following the base pairing rules, the RNA
  polymerase adds the correct sequence of
  nucleotides to the growing RNA molecule
• 4) The RNA strand stops growing when the RNA
  polymerase reaches the STOP signal on the DNA
• 5) The RNA is edited before it is used by the cell

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RNA editing
Introns non-coding segments of RNA Exons
regions of the RNA that code for proteins
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Its your turn.You be the RNA polymerase binding
to this gene
DNA
A T G G C C A T T C G A C G T A
T A C C G G T A A G C T G C A T
RNA
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Then what?

• The mRNA leaves the nucleus and travels to the
  ribosome
• Its code is held in groups of three nucleotides
  (codons)
• One codon codes for one amino acid
• UGCACGAUCGCA
• is read
• UGC-ACG-AUC-GCA

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How do you know what amino acid it codes for?

• There are 20 possible amino acids to choose from
• Example GGA codes for Glycine
• How about
• AUG
• UAU
• UAG

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Translation

• Occurs at the ribosome
• De-codes the message on mRNA
• Amino acids are bonded together in order to build
  a polypeptide (protein)

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Steps of Translation

• 1) mRNA leaves the nucleus and travels to the
  ribosome
• 2) mRNA attaches to the ribosome at the start
  codon
• 3) tRNA attaches the correct amino acid to the
  growing polypeptide (ex mRNA reads AUG ?
  methionine is added)

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Steps of Translation

• 4) tRNA follows the base pairing rules and
  matching the correct anticodon on the tRNA to its
  codon on the mRNA
• 5) The amino acids join together with peptide
  bonds as the ribosome continues to move down the
  mRNA and read its codons
• 6) The ribosome stops when it reaches a stop
  codon on the mRNA

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What is the result of translation? Why is it
important?
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Uh-oh! Cells can make mistakes!!!!

• Mutations
• Gene mutation changes in a single gene
• Substitution
• Insertion
• Deletion

Point mutation
Frameshift mutation
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Mutations

• Chromosomal mutations changes in a whole
  chromosome
• Polyploid individuals have an extra set of
  chromosomes

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Your turn

• Complete the 12-4 worksheet on mutations