DNA Protein

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DNA ? Protein

• Ch. 17

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DNA codes for Proteins

• Studying metabolic defects lead scientists to
  conclude that DNA codes for protein
• Beadle and Tatum (1941)
• Mutated the DNA in bread moldfun!
• Found that when they mutated different genes,
  different proteins were missing
• Broken gene non-functional enzyme
• Without enzyme, essential amino acids could not
  be made, must be supplied

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Experiment
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Human disorders

• Also seen in human disorders
• PKU
• Albinism
• Knock-out mice

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One gene-one enzyme

• Conclusion
• One gene codes for one enzyme
• Not all proteins are enzymes,
• SO
• One gene - one protein
• Many proteins are composed of more than one
  polypeptide,
• SO
• One gene - one polypeptide
• Really even more complicated than that
• Products of genes can be modified in to make more
  than one polypeptide

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Central Dogma

• The flow of genetic information within a cell
• DNA RNA Protein

Transcription
Translation
Replication
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From the nucleus to cytoplasm

• Where are the genes?
• Genes are on chromosomes in the nucleus
• Where are proteins made?
• Proteins are synthesized at ribosomes, in the
  cytoplasm
• How does the information get from the nucleus to
  the cytoplasm?
• Messenger RNA

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What is RNA?

• Similar to DNAmade of nucleic acids, phosphates,
  sugar
• Ribose sugar
• Uracil instead of thymine
• AU
• CG
• Single stranded

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First step in making a protein

• DNA RNA

1. Transcription
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1. Transcription

• One side of DNA is used as a template
• Complementary (matching) strand of RNA is made
• Also called messenger (mRNA)
• Enzyme RNA polymerase

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RNA processing

• Before leaving the nucleus mRNA must be processed
• Editing Some parts of the message taken out
• Tail and cap added for protection

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Second step in making a protein

• DNA RNA Protein

2. Translation
Transcription
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2. Translation

• mRNA message is sent to the Ribosome
• The ribosome translates the messageby connecting
  correct amino acids
• Every 3 RNA bases codes for 1 amino acidcalled a
  codon
• A polypeptide or protein is made

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What do proteins do?

• You tell me
• Lets learn how to use the pipets for our
  transformation lab