Pathology 3240A Lecture 9: Molecular Genetics

• School: Western University
• Department: Pathology
• Course: Pathology 3240A
• Professor: Cheryl Campbell

Document Summary

The central dogma of molecular biology: dna to rna to protein. In germ cells: can be transmitted to progeny; giving rise to inherited diseases, or predisposition to familial cancers. In somatic cells: not transmitted to progeny; giving rise to cancer or congenital malformations: point mutation. Single nucleotide change: missense (changed aa, nonsense (stop codon; truncated protein, silent (unchanged aa, frameshift mutation. Insertion or deletion of nucleotides (generally 1 or 2; not multiples of 3: trinucleotide repeat. Amplification of a 3-nucleotide sequence (highly dynamic, can change in size during gametogenesis, unstable: splicing mutation. Classification by type of mutation: gain of function mutations and loss of function mutations, gain-of-function (mutation gives protein new, toxic properties; mostly dominant) Huntington"s disease: loss-of-function (mutation strongly impairs or completely eliminates protein function; mostly recessive) Cystic fibrosis: exception: haplo-insufficiency: loss of function and dominant inheritance (50% reduction of protein function causes disease) Combinations of mutations cause disease (each mutation alone typically does not cause disease)