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Gene Expression Defines Cells

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  1. Gene Expression Defines Cells http://www.ornl.gov/hgmis

  2. Recall the Central Dogma Info Info Carrier Functional Product DNA RNA PROTEIN

  3. All Information is in DNA http://www.ornl.gov/hgmis

  4. DNA is a Nucleic Acid • Principle information molecules in the cell • Linear polymer of nucleotides (or bases) • Two types • Deoxyribonucleic Acid – DNA • Information storage in cells • Ribonucleic Acid – RNA • Information carrier in cells

  5. Nucleotides in DNA • Three components • Nitrogenous Base (A, C, G, T) • Ribose Sugar • Phosphate

  6. Nucleotide Bases

  7. Nucleotide Detail

  8. DNA and RNA • For DNA bases are A, C, G, T • Sugar is deoxyribose (no OH at 2’ position) • For RNA bases are A, C, G. U • Sugar is ribose (OH at 2’ position)

  9. Phosphodiester Links Nucleotides

  10. Complementary Base Pairing • Holds nucleic acid strands together • H-bonding between complementary bases • This is an interaction that is easily broken • A pairs with T (DNA), (A-U for RNA) • G pairs with C (both DNA and RNA)

  11. Complementary Base Pairing

  12. DNA Structure

  13. DNA Structure Reveals Copying Mechanism

  14. DNA is Transcribed http://commons.wikimedia.org/wiki/Image:DNA_transcription.gif

  15. Transcription Initiation Promoter with Transcription Factors http://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Simple_transcription_initiation1.svg/721px-Simple_transcription_initiation1.svg.png

  16. Transcription and Translation http://stemcells.nih.gov/StaticResources/info/scireport/images/figurea6.jpg

  17. Proteins Primary functional molecules of the cell; execute the tasks directed by the genetic material • Structural molecules (e.g., hair, fingernails, connective tissue) • Transmitting Information between cells (e.g., hormones) • Defense against infection (e.g., antibodies) • Enzymes (catalyze nearly all biochemical reactions)

  18. Building Blocks are Amino Acids • 20 different amino acids in proteins • Chemical properties of side chains determine function • Central carbon atom (Ca) • H atom • Amino group (NH3+) • Carboxyl group (COO-) • R group (side chain)

  19. R-group (Side Chain) • R -group determines identity, function • A.A. are categorized by chemical properties of the side chains 1) Polar (uncharged) = hydrophilic 2) Positively charged (basic) = ionic 3) Negatively charged (acidic) = ionic 4) Nonpolar = hydrophobic

  20. Nonpolar Amino Acids The side chains of these a.a. tend to be located in the interior of proteins, where they are not in contact with water.

  21. Peptide Bond • Links amino acids • Amide linkage between -NH3 and -COO- • Defines amino (N) terminus and carboxy (C) terminus

  22. Protein Structure • Polypeptide (protein) chains fold into globular structure • Defines cracks and crevices that can interact with other molecules • Allows proteins to be enzymes

  23. Enzymes • Enzymes are catalysts • They increase the rate of reactions • This allows rapid synthesis and degradation of products in cells

  24. Building Proteins -Translation • mRNA contains 3 nucleotide codons • Each codon specifies an amino acid • Triplet codons are decoded by tRNA • decoding is base pairing between codon on mRNA and anticodon on tRNA • Each tRNA carries a specific amino acid • codon-anticodon pairing delivers specific aa to the growing polypeptide chain "protein: synthesis." Online Art. Britannica Student Encyclopædia. 10 Aug. 2008  <http://student.britannica.com/eb/art-1692>.

  25. Overview of Gene Expression http://www.ornl.gov/hgmis