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 =
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