BIO 121 Chapter Notes - Chapter 16: The Double Helix, Nitrogenous Base, Pentose
11 Apr 2017
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Document Summary
Griffith experiments (1928: pathogenic and nonpathogenic bacteria, discovers that the nonpathogenic, when mixed with death pathogenic, still become pathogenic they undergo transformation. Transformation: the change in genotype and phenotype due to the assimilation of external dna. Evidence that dna was genetic info came from viruses called phages (consist of little more than dna: hershey and chase, saw phages infect host cells and only dna was transferred. Watson and crick deduces dna as a double helix. 2 antiparallel subunits that run in opposite direction from each other: from 5" to 3" direction, sugar-phosphate chains unwind around outside with nitrogenous bases on the interior that for hydrogen bonds with specific pairs. Adenine/guanine = purines (with 2 organic rings; longer) Thymine/cytosine = pyrimidines (with 1 organic ring; shorter) Nucleotides always link in 5 to 3" position, a covalent bond forms between the carbon at 3" of one nucleotide to the phosphate at 5" of another nucleotide.
