BIOC 3110 Lecture Notes - Lecture 35: Holliday Junction, Phosphodiesterase, Ames Test
19 Nov 2016
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Types of mutations: single, base-pair changes, deletion of nucleotides, insertion of nucleotides, chromosomal rearrangements. How are mutations made: dna replication mutations: Dna replication causes mutations; dna polymerases are efficient and rarely make mistakes because they have exo- nuclease proofreading activity. Mutations typical in cag repeat areas of strand, causes misalignments. The template dna strand is presented, then an rna primer is added. Sometimes if the rna primer dislocates and misaligns from the template strand, it causes a loop in the primer, which pinches up a single nucleotide. This causes an increase in the strand length. The template misaligns, so you do not have that matched piece of rna primer; causes a shortening of the strand, thus deletion: spontaneous dna deamination mutations: Cytosine deamination occurs spontaneously (100x per day in human cell. When cytosine is deaminated in dna, it forms uracil. Or post replication modifications-deamination of methylcytosine to form thymine. Normally cytosine is base paired with guanine.
