Search PubMed⌕ Search

Biomedical subjects

L R Ginzburg

Publications and source records attributed to L R Ginzburg.

13 recordsLinked to original sources
PubMed1984

On the theory of speciation induced by transposable elements.

A simple methematical model describes the invasion of panmictic, sexually reproducing populations by a newly introduced transposon. The model places important constraints on the properties that transposons must have to successfully invade a population and describes the kinetics with which such an invasion will occur. Invasibility conditions serve as a basis for new, detailed scenarios whereby transposon-mediated depression in fitness produces reproductive isolation of populations. These scenarios, in turn, lead to several speculations concerning the role of transposons in evolution.

DNA Transposable Elements↗
PubMed1983

Should individual fitness increase with heterozygosity?

Natural selection influences not only gamete frequencies in populations but also the multilocus fitness structures associated with segregating gametes. In particular, only certain patterns of multilocus fitnesses are consistent with the maintenance of stable multilocus polymorphisms. This paper offers support for the proposition that, at stable, viability-maintained, multilocus polymorphisms, the fitness of a genotype tends to increase with the number of heterozygous loci it contains. Average fitness always increases with heterozygosity at stable product equilibria (i.e., those without linkage disequilibrium) maintained by either additive or multiplicative fitness schemes. Simulations suggest that it "generally" increases for arbitrary fitness schemes. The empirical literature correlating allozyme heterozygosity with fitness-correlated traits is discussed in the light of these and other theoretical results.

Animals↗
PubMed1977

Local consideration of polymorphisms for populations coexisting in stable ecosystems.

The stability problem for multiallelic genetic polymorphisms for n populations coexisting in stable ecosystems is considered. Taking into account only density-dependent interactions a generalization of Fisher's theorem is obtained. Specifically, the average fitness of a population must be locally maximized subject to the constraint that the equilibrium population sizes are fixed if the polymorphism is stable. Further, the quasi-equilibrium population sizes Ni corresponding to fixing the genetic structure of all populations in the ecosystem at various values have extrema at the equilibrium point. Such an equilibrium can be a maximum, minimum or saddle point depending upon the type of ecosystem under consideration. A simple test separating these cases on the basis of the so-called ecosystem matrix is suggested. The general equilibrium problem is reformulated as a maximization problem under some restrictions. Conditions under which the maximized function can be expressed as sigma ni=1 Ni are formulated.

Alleles↗