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Genetic basis for evolution Part I

Genetic basis for evolution Part I DNA model Describe the history of the early discoveries of DNA. A) Friedrich Meischer in 1869 isolated DNA from fish sperm and the pus of open wounds.

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Genetic basis for evolution Part I

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  1. Genetic basis for evolution Part I • DNA model

  2. Describe the history of the early discoveries of DNA. • A) Friedrich Meischer in 1869 isolated DNA from fish sperm and the pus of open wounds. • Since it came from nuclei, Meischer named this new chemical, nuclein. Subsequently the name was changed to nucleic acid.

  3. 1. Early History con’t • Now called deoxyribonucleic acid. • b) Robert Feulgen, in 1914, discovered that fuchsin dye stained DNA. • DNA was then found in the nucleus of all eukaryotic cells.

  4. 1. Early history con’t • c) P.A. Levene 1920 analyzed the components of the DNA molecule. He found it contained four nitrogenous bases: cytosine, thymine, guanine and adenine and a phosphate group. • Basic unit (Nucleotide) was composed of a base attached to a sugar and that the phosphate also attached to the sugar.

  5. 2. Describe the discovery of the DNA model. • Watson and Crick gathered all available data in an attempt to develop a model of DNA structure.

  6. 2. Discovery of DNA 3 D shape • Used Rosaline Franklin’s x-ray diffraction photomicrographs of crystalline DNA extract, the key to the puzzle. • Watson and Crick got all the credit (male scientists vs female).

  7. 3. What is a nucleotide? What components are in nucleotides & what function? • nucleotides  The subunits of nucleic acids ( DNA & RNA) composed of a phosphate, a sugar, and a nitrogen-containing base. DNA made of nucleotides • DNA Bases: Adenine, guanine, cytosine and thymine. • RNA Bases: Adenine, guanine, cytosine and urasil • Paired bases: A….T and C….G always • Some nucleotides are involved in information storage (as nucleotides in DNA), protein synthesis (as nucleotides in RNA), and energy transfers (as single nucleotide ATP)

  8. 4. Draw a Nucleotide Basic unit P…….A S Link to additional nucleotides

  9. 5. Draw a DNA molecule P……A --- T………P S S P……G--- C………P S S P……C --- G……..P S S P…….T --- A……. P S S Key P = phosphate S = sugar (deoxyribose A = adenine base T = thymine base G = guanine base C = cytosine base

  10. 5. Draw a DNA molecule con’t

  11. 6. What is a codon and why is it important? Important in protein synthesis and replication of DNA • 1. DNA nucleotide bases arranged in triplets of 3 bases, code for amino acids which are the base for proteins. Ex: GGC TCA CCC GGG TTA ACC

  12. 7. How does DNA function in evolution? DNA codes for proteins used in all cell functions. • Proteins can be structural – muscle • Enzymes – controlling all biochemical reactions • Hormones – control body functions

  13. 7. Proteins & evolution con’t • All variation in traits based on differences in protein structures or biochemical pathways controlled by enzymes • Gene based traits selected for by environment. *White coat vs brown (biochemical, enzyme) *run faster (muscles & biochemical) *larger body size (structural proteins) * adapted to high temperature (enzymes) *more aggressive – increase testosterone (hormones)

  14. 8. Describe process of protein synthesis. • Step 1: DNA contains message in codons • Step 2: Transcription – DNA code given to RNA messenger. • Step 3: RNA copies DNA message and carries out of nucleus to Endoplasmic Reticulum • Step 4: Translation -RNA joins up with transfer RNA which carries protein subunits called Amino Acids. Translates code from DNA. Occurs in ribosomes attached to endoplasmic reticulum. • Step 5: Amino Acid subunits combined into proteins in cytoplasm.

  15. 8. Protein synthesis continued

  16. 8. Describe process of protein synthesis. • DNA……mRNA…..tRNA….protein • Transcription translation

  17. Photos & refs • http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookDNAMOLGEN.html

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