Lecture.19.Fall.2013

Despite differences in size anatomy and physiology

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Unformatted text preview: ne that showed sequence homology with tinman • This gene (Nkx2.5) had no previously known function. • sequencing revealed a mutation in the gene in this family, present in every individual with a heart defect The human tinman homolog • Many people with congenital heart defects have a mutation in tinman. • Despite differences in size, anatomy and physiology, humans and flies use the same genes to make a heart. • Incidentally, this is some of the best modern evidence for the Theory of Evolution by Natural Selection Mutations give clues to normal gene function • The tinman story illustrates the importance of studying mutations. • Geneticists study mutations to demonstrate what the normal function of a gene is - what happens when you break it? • Analysis of mutants is often a source of key insights into important biological processes. Mutations give clues to normal gene function • Steps in discovering a gene involved in heart development: 1. Isolation and study of fly mutants in which no heart developed 2. Mapping the mutation to a single gene (in flies) using linkage analysis 3. Determination of the normal function of the gene (in flies) 4. Identification of mutant humans with defects in heart development 5. Mapping the human mutations using linkage analysis Studying mutations leads to an understanding of normal gene function • Steps in discovering a gene involved in heart development: 6. Identification of a good “candidate gene” based on sequence similarity to the fly gene homology 7. Sequencing that gene in the mutant humans and identification of a mutation 8. The wild-type gene is necessary for heart development and likely mediates heart development in normal humans/flies. 9. This allows the development of therapeutics by identifying drug targets and understanding how we want to affect them (e.g. stimulate or repress their functions or interactions). The importance of mutations changes in sequence Mutations are inherited changes in genetic information. • Mutations are bad: – Many mutations have detrimental effects • But mutations are al...
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