title: Measuring bidirectional mutation.
abstract: The estimation of mutation rates is usually based on a model in which mutations are rare independent Poisson events. Back-mutation of mutants, an even rarer event, is ignored. In the hypermutating B cells of the immune system, mutation between phenotypes exhibiting, vs. not exhibiting, surface immunoglobulin is common in both directions. We develop three strategies for the estimation of mutation rates under circumstances such as these, where mutation rates in both directions are estimated simultaneously. Our model for the growth of a cell culture departs from the classical assumption of cell division as a memoryless (Poisson) event; we model cell division as giving rise to sequential generations of cells. On this basis, a Monte-Carlo simulation is developed. We develop also a numerical approach to calculating the probability distribution for the proportion of mutants in each culture as a function of forward- and backward-mutation rates. Although both approaches are too computationally intensive for routine laboratory use, they provide the insight necessary to develop and evaluate a third, 'hand-calculator' approach to extracting mutation rate estimators from experiments of this type.
authors.affiliation: Centenary Institute, Building 93, Royal Prince Alfred Hospital, Missenden Road, Camperdown, Sydney, NSW 2042, Australia.
authors.forename: C
authors.initials: C
authors.lastname: Jolly
authors.forename: A J L
authors.initials: AJ
authors.lastname: Cook
authors.forename: J
authors.initials: J
authors.lastname: Raftery
authors.forename: J
authors.initials: J
authors.lastname: Raferty
authors.forename: M E
authors.initials: ME
authors.lastname: Jones
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology*; D002478:Cells, Cultured; D003627:Data Interpretation, Statistical; D007075:Immunoglobulin M / Q000235:genetics; D008957:Models, Genetic; D009010:Monte Carlo Method; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D016012:Poisson Distribution; D011336:Probability
chemical_list: D007075:Immunoglobulin M