05 Mutations and DNA repair mechanism

Exon skipping results from mutation at the splice

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Unformatted text preview: results from mutation at the splice site *Splicing of an intron requires an essential signal: for example, "GT........AG". If the splice acceptor site AG is mutated, the splicing machinery will look for the next acceptor site. As a result, the exon between two introns is also removed. T G C. INSERTION: addition of one or more nucleotides in the DNA *if the number of inserted bases is not a multiple of 3, it will cause frameshift, resulting in serious consequences *some diseases caused by insertion: Huntington disease, Kennedy disease, Myotonic dystrophy, etc. *deletion and insertion are usually caused by Replication Slippage C Consequences: 1. Silent mutation- no effect on the amino acid sequence of the protein 2. Missense mutation- results in the incorporation of a different amino acid in the protein. The protein may be functional, partially functional or non-functional 3. Nonsense mutation- results in the premature appearance of a stop codon resulting in the shorter protein that is likely to be non-functional Isidro C. Medina Jr....
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