Lecture.20.Fall.2013

Gene has lost function normal activity is reduce and

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Unformatted text preview: partial absence of normal protein function. gene has lost function, normal activity is reduce and no longer functional • Alters the structure of the protein so that it no longer works correctly. • Frequently caused by early nonsense mutations, which truncate the protein. • Can also result from mutations in regulatory regions that affect transcription, translation, or splicing of the protein. loss of funtion can happen in regions of regulation Loss-of-function mutations Frequently recessive, so that an individual diploid organism must be homozygous to exhibit the mutant phenotype. or dblt=y heterozygous Hypomorphic: mutations that reduce but do not eliminate gene function partial loss of function, but not completely remove function “Null” or “complete loss of function”: mutations that completely eliminate gene function early truncation: stop replication early=null “Haploinsufficient” - null mutations that are dominant, due to a requirement for two copies of the mutated gene non recessive mutation: hlf is not enough, you need two copies. these are dominant because the wild type allele ex: hyperchloseteriemia: cholesterol Loss-of-function and Gain-of-function mutations • Gain-of-function mutations: results from acqusition or overactivity of gene • result in a new function, or • cause gene expression in an inappropriate tissue or • at an inappropriate time in development • or under inappropriate cellular conditions. Gain-of-function mutations • Example: a mutation might occur in a gene that encodes a receptor for a growth factor that changes the protein such that it is active in the absence of the growth factor constant division, cancer causes • Would stimulate growth/cell division regardless of conditions = dominant Los...
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