Single gene mutations

Major modes of inheritance of single-gene mutations are ... 

For multifactorial diseases, the recurrence risk decreases rapidly for more remotely related relatives. For example, one study of autism reported a sibling risk of 4.5%, an uncle-niece risk of 0.1%, and a first-cousin risk of 0.05%. In contrast, the risk of carrying a single-gene mutation decreases by only 1/2 with each successive degree of relationship (i.e., 50% chance for siblings, 25% for unde-niece relationships, and 12.5% for first cousins). 

In AML FLT3 mutations are the most abundant single-gene mutations. There is no difference in prevalence of FLT3 mutations in groups of radiation-... 

Figure 5.7. There are many examples now known of the synthesis of NPs via matrix pathways (see also Figure 9.3). However, a nice example of the benefit of such flexibility was revealed when a mutant of spearmint that had smelled more like peppermint was studied.A comparison of the terpenes in both plants revealed that the single gene mutation had not resulted in a single chemical change but multiple changes, in the mutant plant, a hydroxyl group was added to the 3-position of the cyclohexene ring of limonene while the wild-type hydroxylated the 6-position. Some of the other wild-type tailoring enzymes in the mutant did not discriminate fully between the 3- and 6-hydroxylated products so a new family of NPs were produced which gave the mutant plant an odour of peppermint.

Single gene mutations apparently affect each isozyme, for the mobility of all the bands are affected without altering the spacing (44, 67, 70). Levinthal et al. (70) therefore concluded that all of the isozymes were coded for by the same gene. 

Since natural selection cannot preserve nonfunctional characters, the most obvious implication of the facts would seem to be that a stepwise evolution of biosyntheses, by the selection of a single gene mutation at a time, is impossible.13... 

Beutler E. Gaucher disease as a paradigm of current issues regarding single gene mutations of humans. Proc Natl Acad Sci U.S.A. 90 5384-5390,1993. 

L7. Lithgow, G. J., White, T. M., Melov, S., and Johnson, T. E., Thermotolerance and extended life-span conferred by single gene mutations and induced by thermal stress. Proc. Natl. Acad. Sci. USA 92 7540-7544 (1995). 

Giroux, M. J., Shaw, J., Barry, G., Cobb, B. G., Greene, T., Okita, T., and Hannah, L. C. 1996. A single gene mutation that increases maize seed weight. Proc. Natl. Acd. Sci. USA, 93, 5824-5829. 

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