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James F Crow

Publications and source records attributed to James F Crow.

At least 19 recordsLinked to original sources
PubMed2006

Age and sex effects on human mutation rates: an old problem with new complexities.

Base substitution mutations are far more common in human males than in females, and the frequency increases with paternal age. Both can be accounted for by the greater number of pre-meiotic cell divisions in males, especially old ones. In contrast, small deletions do not show any important age effect and occur with approximately equal frequency in the two sexes. Mutations in most genes include both types, and the sex and paternal age effect depends on the proportion of the two types. A few traits, of which Apert Syndrome is best understood, are mutation hot spots with all the mutations occurring in one or two codons, usually at one nucleotide. They occur with very high frequency almost exclusively in males and the frequency increases rapidly with paternal age. It has been suggested that the mutant cells have a selective advantage in the male germ-line prior to meiosis. Evidence for this surprising, but important, hypothesis is discussed. A possible mechanism is the conversion of asymmetrical stem-cell divisions into symmetric ones. Some traits with complex etiology show a slight paternal age effect. There is also a short discussion of the high deleterious mutation rate and the role of sexual reproduction in reducing the consequent mutation load.

Adolescent↗
PubMed2005

Essay: early American genetics journals.

Before the Second World War, there were only two North-American journals exclusively devoted to genetics - the Journal of Heredity and Genetics. In the late 1940s, Genetics spawned two progeny - the American Journal of Human Genetics and Evolution. This article recounts the early days of these journals, their influential and often colourful founding editors, and their contents. It emphasizes the contrast between those years, when a reader had a realistic chance of keeping up with the whole field, and the current plethora of journals that makes it impossible to keep up with even the tables of contents.

Genetics↗
PubMed2005

Timeline: Hermann Joseph Muller, evolutionist.

This essay is dedicated to the proposition that Hermann Joseph Muller, widely regarded as the greatest geneticist of the first half-century of the subject, was also one of the greatest evolutionists of this period. His Nobel Prize-winning work, which showed that radiation increases the mutation rate, is in every genetics textbook, and his prescient ideas have influenced almost every aspect of the discipline. Here I emphasize his less well-known contribution to the neo-Darwinian theory of evolution.

Biological Evolution↗
PubMed2003

On the persistence and pervasiveness of a new mutation.

It has frequently been assumed that the persistence of a deleterious mutation (the average number of generations before its loss) and its pervasiveness (the average number of individuals carrying the gene before its loss) are equal. This is true for a particular simple, widely used infinite model, but this agreement is not general. If hs >> 1/(4N(e)), where hs is the selective disadvantage of mutant heterozygotes and N(e) is the effective population number, the contribution of homozygous mutants can be neglected and the simple approximate formula 1/hs gives the mean pervasiveness. But the expected persistence is usually much smaller, 2(log(e)(1/2hs) + 1 - gamma) where gamma = 0.5772. For neutral mutations, the total number of heterozygotes until fixation or loss is often the quantity of interest, and its expected value is 2N(e), with remarkable generality for various population structures. In contrast, the number of generations until fixation or loss, 2(N(e)/N)(1 + log(e)2N), is much smaller than the total number of heterozygotes. In general the number of generations is less than the number of individuals.

Genetics, Population↗