BIOS 10161 Lecture 32: Gene mutation and medicine
1 Dec 2016
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Spontaneous mutations occur with no outside influence (cellular processes are imperfect: several mechanisms alter dna spontaneously, bases can have different structures may form tautomers; a rare tautomer can pair with the wrong base. Chemical reactions may change bases (e. g. , loss of amino group deamination: c"s (cid:272)a(cid:374) (cid:271)e(cid:272)o(cid:373)e (cid:862)methylated(cid:863) a methyl group is added to the cytosine. This is part of an epigenetic process called methylation (creative i know). It is a major means of sile(cid:374)(cid:272)i(cid:374)g ge(cid:374)es that are(cid:374)"t (cid:374)eeded i(cid:374) a (cid:272)ertai(cid:374) tissue type, et(cid:272): however, that methylation can lead to the spontaneous change to thymine which error proofing mechanisms fail to detect. This causes mutations in daughter cells, particularly in genes that were turned off. Interestingly, when these methylated cytosine become thymine, there is no longer a methylation and the gene is no longer turned off. Errors in replication by dna polymerase: can be a mechanism for generation of transversion.
