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Biomedical subjects

E A Murphy

Publications and source records attributed to E A Murphy.

At least 127 records · Page 7Linked to original sources
PubMed1981

Human genetics teaching in U.S. medical schools.

Information about instruction in genetics was obtained fron 103 of the 107 U.S. four-year medical schools. Seventy-two percent of the schools provide a compulsory course in genetics, but there was great variation in duration, content, departmental responsibility for giving the course, and in the disciplines of those doing the teaching. The variability in the number of hours devoted to teaching genetics was reflected in the competence of the students in giving correct answers to questions on genetics posed by the National Board of Medical Examiners. Electives and continuing education courses on genetics are given by two-thirds and one-half of the schools, respectively; but the subject receives very little attention in departments of preventive, community, or family medicine or in schools of allied health sciences. These findings suggest that genetics has not yet found a natural and comfortable context in the curricula of U.S. medical schools.

Education, Medical↗
PubMed1980

The quantitative genetics of disease: ambiguities.

Here I review briefly some terms appropriate to the formal discussion of the genetics of disease. The motive for writing is that at least three kinds of participating experts are involved: pathologists, geneticists, and statisticians. Not only may some of the terms used in one field be unfamiliar to experts from another, the same term may be used in diverse ways among, or even within, fields. Such ambiguity may create illusory understanding or even frank confusion.

Genetics, Medical↗
PubMed1980

Reduction of bias in estimating the frequency of recessive genes.

The standard approach to estimating the frequency of a completely recessive autosomal gene is to use the maximum-likelihood estimator (MLE), q = square root q2. Since the expectation oof Q using MLE is systematically less than the true value, this estimator always gives a negatively biased estimate of q. Here we describe the bias associated the MLE over a range of q and N values, explore some of the properties of this estimator, and propose new estimators which reduce the bias. We also describe some of the new estimators' properties, as well as the remaining bias associated with them for varying q and N values. We further propose one of these estimators as the one which most effectively reduces bias over a specific q value range of approximately .005 to .05, and which is less biased than JLE over essentially all q and N values. The proposed estimator also is directly compared with MLE in calculating various available estimates of q, demonstrating the percentage of reduction in bias achieved. This reduction varies from negligible for estimates of q above .3 and N greater than 100, to a 23% reduction in bias for a q value of .09 and an N value of 215.

Gene Frequency↗
PubMed1980

Hereditary polyposis coli. III. Genetic and evolutionary fitness.

The numbers of progeny born to 355 patients with heritable polyposis of the colon and to 315 related, but normal, subjects, all old enough to have completed their families, are presented, as well as data on 432 subjects still young enough to have more children. Two main indices are used: mean family size ("genetic fitness") and the complement of the extinction probability of the line ("evolutionary fitness"), both of which suppose a steady state. Point- and interval-estimates (the latter derived by an extension of Stigler's method) are furnished. It is estimated that the probability a new mutant gene will persist is one in four for Gardner syndrome, one in 20 for familial polyposis coli, and 0 for Peutz-Jeghers syndrome. There is evidence of bimodality in family size, suggesting voluntary infertility in a proportion of subjects. The data confirm our provisional working assumption that most families are completed by the time women are in their mid-40's and men in their mid-50's.

Adolescent↗
PubMed1979

Finite sample properties of maximum likelihood estimates of the recombination fraction in double backcross matings in man.

The properties of the maximum likelihood estimator (MLE) of the recombination fraction, theta, based on various numbers and sizes of sibships derived from double backcross matings are exactly explored where the coupling phases are presumed equally likely (which for two-generation data is generally the case). The results indicate that for large values of theta the expectations are severely biased. The bias, variance, and measures of normality of the MLE behave erratically for small sizes and numbers of sibships. The implications for chromosome mapping are discussed.

Consanguinity↗
PubMed1979

Segregation of noisy Mendelian traits and the effect of age-dependence: a prolegomenon.

A discussion of the primordial confusion between the multiplicative Galtonian ("lognormal") trait and the imperfectly segregating Mendelian trait is laid out from a probabilistic standpoint. Several criteria used in comparing them (bimodality; bitangentiality; goodness of fit to the multinomialized form of the distribution; cumulants of the distributions) are reviewed and the inadequacy of their probabilistic properties discussed in some detail. The logical asymmetry of the normalized score ("Roberts" correction") and hence its invalidity as a criterion for distinguishing between the models is pointed out. The form of a mixture of two Gaussian distributions with fixed and equal variances but with differing age-dependent means ("the Platt model") is explored. The epistemological implications are exhibited. As a first step to restoring symmetry, a general model is proposed of which these and other models in wide use emerge as special cases. No attempt is made to deal here with the statistical aspects of the problem.

Age Factors↗
PubMed1979

Where are we going?

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Genetic Diseases, Inborn↗
PubMed1979

Seven snobberies.

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Attitude of Health Personnel↗