1362-SU09-Lecture-3-_39799

1362-SU09-Lecture-3-_39799 - DNA: The Carrier of Genetic...

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DNA: The Carrier of Genetic Information organ’s studies showed that genes are located on chromosomes; Morgan s studies showed that genes are located on chromosomes; the components of chromosomes proteins and DNA were the 2 candidates for the molecule of inheritance. –t h e large variety of protein types led to belief that these were the information storage molecules of heredity. iden ce s pported DNA as the genetic aterial Evidence supported DNA as the genetic material: Griffith : Pneumococcus (bacteria); showed that material passed from virulent strain to non virulent strain conferring disease causing characteristics to that non virulent strain; termed the “transforming principle”. very isolated Griffiths’ “transforming Avery : isolated Griffiths transforming principle” from Pneumococcus and identified it as DNA Hershey/Chase : studied bacteriophages; demonstrated DNA, not protein, carried the information to produce viable phage. p pg Franklin, Watson & Crick : elucidated DNA structure & “cracked” the genetic code
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Structure of DNA Franklin : X-ray crystallography; used to determine molecular structures of chemicals. – Method: (1) prepare crystals; (2) bombard with X-rays. Atoms in molecule bend & spread X-ray waves; the resultant pattern is captured on a photographic plate. X-ray crystallography – Certain molecular features yield predictable patterns that one can of DNA piece together to estimate the overall structure. atson & Crick sed Watson & Crick used Franklin’s data, along with aking molecular models, to making molecular models, to figure out the structure of DNA. Chargaff: chemical analysis of g y DNA; %A=%T, %G=%C.
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Structural Model of DNA Double Helix The double helical arrangement of DNA. hink of a ladder Think of a ladder that is twisted in a coil. Exterior of DNA: gar hosphate Sugar Phosphate Backbone Interior: itrogenous Nitrogenous bases
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3’OH 5’P DNA is a charged Features of NA Hydrogen molecule: negative charge on the DNA bonding between bases holds the NA strand phosphates. DNA is acidic. Chargaff’s Rule of base- airing DNA strand together. Note that the DNA strands are oriented pairing : Apairs±with±T G pairs with C ermed in opposite directions. This is termed Termed complimentary base pairing ; antiparallel.
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1362-SU09-Lecture-3-_39799 - DNA: The Carrier of Genetic...

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