DNAA Code for Life

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DNA?A Code for Life

• 1. Replication

• Protein Synthesis
• Transcription
• Translation

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Nucleic Acids

• Found in nucleus is chromatin (or chromosomes
  during mitosis) made up of DeoxyriboNucleic Acid.
• Structure proposed by Watson and Crick (1953)
• Contains instructions for construction of
  proteinsprimary cellular worker molecules.

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Structure of DNA

• Double Helix twisted ladder (see previous)
• Monomer? nucleotides (phosphate, sugar, and base)
• Sugar/Phosphate railing
• Bases (A,T,C,G)

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Nitrogenous Bases

• Purines
• Two Nitrogen-Containing Rings
• Larger than pyrimidines
• Adenine
• Guanine

• Pyrimidines
• One Nitrogen-Containing Ring
• Smaller
• Thymine
• Cytosine

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Base Pairs

• Adenine always bonds with Thymine
• Cytosine alwys bonds with Guanine
• Hydrogen bonds join bases with one another along
  the central axis of the DNA molecule

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DNA Replication (during S phase)

• Enzyme (helicase) unzips DNA by breaking hydrogen
  bonds.
• 2. Free floating nucleotides adjoin exposed
  bases of two DNA strands (DNA polymerase).

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Protein Synthesis

• DNA?mRNA?Protein

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Protein Synthesis Big Picture
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Protein Synthesis Two Steps

• Transcription
• Consider parts of word
• Happens in nucleus
• Copy DNA to RNA because DNA cant leave nucleus
  (why?)

• Translation
• Consider what it means to translate
• Protein construction from RNA code (which
  originally came from DNA).
• Occurs at site of ribosome/RNA attachment (ER or
  free)

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Transcription Making an RNA Copy

• First make mRNA from DNA template
• m stands for messenger (which can leave
  nucleus)
• U replaces T in mRNA
• Sugar is ribose instead of deoxyribose

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Transcription

• DNA unzipped.
• RNA polymerase attaches free ribonucleic acid
  nucleotides to template strand of DNA
• As mRNA is constructed DNA is zipped back
  together.

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Transcription
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Step 2 Translation

• Translating DNA message (now in mRNA) to create a
  chain of amino acids (ultimately, protein).
• Relies on t(transfer)RNA and Ribosomes
  (containing proteins and r(ribosomal)RNArequired
  to latch onto mRNA).

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Translation

• mRNA is read in codons?like words
• Consist of three mRNA bases
• Protein construction starts when Ribosome
  attaches to Start codon (AUG)
• Construction stops at Stop codon (UAG, UGA, or
  UAA)

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Translation

• mRNA is messenger from nucleus.
• Ribosome draws attention to mRNA.
• tRNA carries amino acids to codons on mRNA
  strand to assemble protein chain.

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Translation

• After attaching to Start codon, ribosome
  signals tRNA with appropriate anticodon.
• tRNA carries amino acid.
• Once done, ribosome moves on, signalling
  additional tRNAs (w/ amino acids) to add new
  amino acids to growing chain.
• This sequence ends at Stop codon

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Translation
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The DNA?RNA?Protein Language
If a strand of DNA consists of the bases,
Thymine, Adenine, and Cytosine, what would be the
mRNA codon? The tRNA anticodon? The amino acid?
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A Parting Cartoon

• Attempt to identify the characters roles in a
  cell.