BI111 Lecture Notes - Lecture 1: Guanine, Thymine, Cytosine

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11 Jan 2016
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Lecture 1 – Monday January 4, 2016
DNA as repository of genetic information
Pyrimidines
oCytosine
oThymine
Purines
oAdenine
oGuanine
DNA Replication is Accurate
Double helix helps maintain accuracy
oWhen replication occurs, double helix unzips, old strands
are used as a template
Cell has enzymes that help correct errors (mismatched base-
pairs, etc.)
Mutation Rates
Mutations allow for genetic variation, without mutations, there
would only be one species on Earth
Vary within and between taxa
Vary with environmental conditions
Higher in RNA viruses (10-3 to 10-5 mutations base-1 generation-1)
than in DNA viruses (10-6 to 10-8)
oSince RNA is only one-stranded
Higher in mitochondrial DNA (3x10-6 to 2.7,x10-5) than in genomic
DNA
Higher in asexual species than sexual species
In humans approx. 1.1x10-8 mutations, per site per generation
There are a lot of mutations
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