BIO 213-F09 - Lecture 3 - Genetics DNA & RNA

BIO 213-F09 - Lecture 3 - Genetics DNA & RNA - Genetics...

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Unformatted text preview: Genetics I Genetics I Lecture Overview – DNA • Structure • Replication – Protein Synthesis • Types of RNA • Transcription • Translation – Mendelian Genetics The Hershey and Chase experiments showed DNA is the genetic material, not proteins A. True B. False Structure of Nucleotides in DNA • Each nucleotide consists of – Deoxyribose (5-carbon sugar) – Phosphate group – A nitrogen-containing base • Four bases – Adenine, Guanine, Thymine, Cytosine Nucleotide Bases phosphate group deoxyribose ADENINE (A) THYMINE (T) CYTOSINE (C) GUANINE (G) Rosalind Franklin’s Work • Was an expert in x-ray crystallography • Used this technique to examine DNA • Concluded that DNA was some sort of helix • Phosphate bonds were on the outside of the molecule Rosalind Franklin 1920-1958, ca. 1950 Watson-Crick Model • DNA consists of two nucleotide strands – Molecule is a double helix • Strands run in opposite directions – antiparallel • Strands are held together by hydrogen bonds between bases Watson-Crick Model http://www.youtube.com/watch?v=qy8dk5iS1f0 In a DNA molecule, the A. Backbone is sugar and phosphate molecules B. Bases are covalently bonded to the sugars C. Sugars are covalently bonded to the phosphates D. Bases are hydrogen-bonded to one another E. All of these are correct DNA Structure Helps Explain How it Duplicates • DNA is two nucleotide strands held together by hydrogen bonds • Hydrogen bonds between two strands are easily broken • Each single strand then serves as template for new strand DNA Replication new new old old • Each parent strand remains intact • E v e r y D N A molecule is half “old” and half “new” http://www.youtube.com/watch?v=hfZ8o9D1tus &feature=related Each old strand serves as the template for complementary new strand “Semiconservative” Same two steps produce ALL proteins: 1) DNA is transcribed to form RNA – Occurs in the nucleus – RNA moves into cytoplasm 2) RNA is translated to form polypeptide chains – Occurs at the ribosome Steps from DNA to Proteins Three Classes of RNAs • Messenger RNA (mRNA) – Carries protein-building instruction • Ribosomal RNA (rRNA) – Major component of ribosomes • Transfer RNA (tRNA) – Delivers amino acids to ribosomes RNA differs from DNA by: A. The 5 carbon sugar B. It is single stranded C. By one nitrogenous base D. All of the above are so correct A Nucleotide Subunit of RNA sugar (ribose) phosphate group uracil (base) Base Pairing During Transcription • A new RNA strand can be put together on a DNA region • C pairs with G • Uracil (U) pairs with adenine (A) • N o t h y m i n e Transcription & DNA Replication • Like DNA replication – Nucleotides added in 5’ to 3’ direction • Unlike DNA replication – Only small stretch is template – RNA polymerase catalyzes nucleotide addition – Product is a single strand of RNA http://media.pearsoncmg.com/bc/bc_campbell_biology_7/media/interactivemedia/activities/load.html?17&A http://bcs.whfreeman.com/thelifewire/content/chp12/1202001.html How does transcription begin? How does transcription begin?...
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This note was uploaded on 06/15/2010 for the course BIO 213 taught by Professor Lee during the Fall '08 term at Cal Poly.

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BIO 213-F09 - Lecture 3 - Genetics DNA & RNA - Genetics...

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