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The time course of spontaneous mutation frequency from middle to late adulthood was measured in four different tissues of the mouse. [8] Mutation frequencies in the cerebellum (90% neurons) and male germ cells were lower than in liver and adipose tissue.
The human germline mutation rate is approximately 0.5×10 −9 per basepair per year. [1] In genetics, the mutation rate is the frequency of new mutations in a single gene, nucleotide sequence, or organism over time. [2] Mutation rates are not constant and are not limited to a single type of mutation; there are many different types of mutations.
The frequency of mutations in mouse somatic tissue (brain, liver, Sertoli cells) was compared to the mutation frequency in male germline cells at sequential stages of spermatogenesis. [3] The spontaneous mutation frequency was found to be significantly higher (5 to 10-fold) in the somatic cell types than in the male germline cells. [3]
Treatment of this mouse model with the procarcinogen azoxymethane (AOM) leads to formation of dysplastic microadenomas in the proximal but not in the distal colon. Thus the K-ras G12D mutant is a valuable mouse model of proximal colon carcinogenesis. Mutation in the Muc2 gene causes adenomas and adenocarcinomas in the intestine of mice. [24]
[citation needed] The mutation frequency of female mouse germ line cells, like male germ line cells, is also lower than that of somatic cells. [49] Low germ line mutation frequency appears to be due, in part, to elevated levels of DNA repair enzymes that remove potentially mutagenic DNA damages. Enhanced genetic integrity may be a fundamental ...
The frequency = + of normal alleles A increases at rate / due to the selective elimination of recessive homozygotes, while mutation causes to decrease at rate (ignoring back mutations). Mutation–selection balance then gives p B B = μ / s {\displaystyle p_{BB}=\mu /s} , and so the frequency of deleterious alleles is q = μ / s {\displaystyle ...
Since the mutations in the T-stock mouse were recessive, the progeny would have a wild type phenotype (as a result of crossing a mutant [e.g.s/s mutant male] to a wild type female [+/+]). Thus with any progeny carrying a mutation induced by radiation at one of the 7 loci, would exhibit the mutant phenotype in the first generation itself.
Identifying and studying mutations that occur often reveals information about the virus or bacterium being studied. Accordingly, after serial passage has been performed it can be valuable to compare the resulting virus or sample of bacteria to the original, noting any mutations that have occurred and their collective effects.