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What are chromosomes made of ?

What are chromosomes made of ?. By mass, chromosomes are about half protein and about half DNA If genes are on chromosomes, are they protein or DNA or perhaps a mix?. Basic chemistry of DNA and protein. Proteins : What are the subunits of protein?

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What are chromosomes made of ?

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  1. What are chromosomes made of?

  2. By mass, chromosomes are about half protein and about half DNA • If genes are on chromosomes, are they protein or DNA or perhaps a mix?

  3. Basic chemistry of DNA and protein Proteins: • What are the subunits of protein? • How many different types of subunit are there?

  4. General structure of an amino acid

  5. DNA • DNA was discovered in 1869 by Friedrich Miescher, a German Chemist. Extracted from the nucleus. • DNA has subunits. • How many different subunits are there?

  6. The basic structure of DNA and RNA determined by Levene in the 1920’s

  7. General structure of a nucleotide

  8. Levene’s tetranucleotide theory • Logic behind the theory— • Genetic information needs to be complex • More complexity possible in proteins than in DNA—he suggests DNA plays a role as ‘scaffolding’, a repeating sequence of 4 bases • The evidence? Approximately equal amounts of each of the 4 bases found in DNA

  9. Avery, MacLeod and McCarty, 1944 • Assumption: Protein is the genetic material • Plan: if ‘transforming principle’ treated chemically to remove protein, it should lose its power – removed all but 0.02% • Problem: It didn’t

  10. Avery, MacLeod and McCarty, cont. • After chemically removing protein, ‘transforming principle’ still able to convert rough bacteria to smooth bacteria • After treatment with proteinase, ditto • After treatment with RNAase, ditto • After treatment with DNAase –’transforming principle’ activity destroyed • FIRST PAPER SUPPORTING DNA AS GENETIC MATERIAL

  11. Tetra nucleotide theory accepted for nearly 30 years • What finally shifted thought away from protein as the genetic material to DNA as the genetic material? • The ‘transforming principle’ of Griffith, using ‘Rough’ and ‘Smooth’ bacteria in 1928 • Avery, MacLeod and McCarty, 1944stripped away protein without destroying the transforming principle

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