BIOA01H3 Lecture 1: Module 3 Genetics Lec 1-12
18 Jan 2018
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G(cid:396)iffith (cid:272)alled this p(cid:396)i(cid:374)(cid:272)iple (cid:862)the t(cid:396)a(cid:374)sfo(cid:396)(cid:373)i(cid:374)g p(cid:396)i(cid:374)(cid:272)iple(cid:863), (cid:271)e(cid:272)ause so(cid:373)ethi(cid:374)g f(cid:396)o(cid:373) the heat-killed pathogenic bacteria must have transformed the living non-pathogenic bacteria to make them deadly; Prepared identical solutions of heat-killed s- strain (virulent) bacteria. Lysed the cells and collected the cell contents. Added 3 different enzymes: proteinases (to destroy protein); ribonucleases (to destroy rna) and deoxyribonucleanases (to destroy dna). Each solution was then mixed with r-strain (non- virulent) cells. The only extract that did not cause transformations of the r-strain was the one treated with the dna-destroying enzyme. The modern dna model: two polynucleotide strands twist around each other to form a double helix. Each polynucleotide strand has a backbone of alternating phosphate groups and sugars: the two strands of dna are complementary to each other a purine molecule always pairs with a pyrimidine molecule. Specifically, a pairs with t and c pairs with g: hydrogen bonds link each complementary base pair.
