Effect Of Population Subdivision Research Articles

The STR polymorphism (AAAAT)n within the intron 1 of the tumor protein 53 (TP53) locus in 17 populations of different ethnic groups of Africa, America, Asia and Europe

The STR (AAAAT)n within intron 1 of the TP53 locus was screened in 17 populations from 3 main ethnic groups: Europeans, Asiatics, and Africans, and from the hybrid population of Costa Rica (1968 samples). Three alleles, 126/7 (bp/copies of the repeat), 131/8 and 136/9 were the most prevalent in all populations. Other alleles rarely reached frequencies of 10% or higher. Observed heterozygosities ranged between 0.351 and 0.829. Patterns of diversity fit well with both the geographic origin of the samples and the history of the populations screened. A statistical test suggests that single-step mutational events have been the main mechanism producing new alleles at this locus. Fixation indexes (R(ST)) for this marker showed an effect of population subdivision on divergence only within the Asiatic group; they were insensitive at the level of major ethnic groups as well as within Africans and within Europeans.

Sero-genetic Profile and Phylogenetic Relationships of Tribes of Rajasthan

Genetic structure and polygenetic relationship of six numerically larger endogamous tribes, Mina, Bhil, Garasia, Damor and Kathodi of Rajasthan, who exhibit varied ethnographic history , have been investigated using 12 sero-genetic polymorphic marker systems viz. A1A2BO, MNSs, Rhesus, Duffy, Lewis, Kell, Kidd, HP, TF, GPI, G6PD deficiency and HB variants. Genetic differentiation with respect to studied genes has been observed small (except for HB* variants and G6PD*Def, which may be under the influence of natural selection) among the studied tribes and it appears that there has been little effect of population subdivision on these genes or late divergence of these populations from one another. The studied tribes make two main clusters, one of Mina and Saharia, other of Bhil, Damor, Garasia and Kathodi. Within the later cluster Bhil and Damor are closest joined by Garasia and then Kathodi. The present study partially supports the ethnographer 's views of their origin and divergence.

Testing for kinship in a subdivided population

The effect of population subdivision on the determination of kinship of any two persons is investigated in this paper. Expressions of the joint genotype probabilities and likelihood ratios on kinship testing are reported. Two real cases are analysed using the Hong Kong Chinese population data and the Spanish data. Various kinds of relationships are investigated for illustration.

What is the magnitude of the subpopulation effect?

The effect of population subdivision on estimated match probabilities has been raised [Nature 339 (1989) 501; Am. J. Hum. Genet. 48 (1991) 819; Science 254 (1991) 1921]. Previous work [J. Forensic Sci. 39 (1994) 319; J. Forensic Sci. 39 (1994) 988; Am. J. Hum. Genet. 55 (1994) 533] has compared product rule estimates from differing databases and found that the “subpopulation” error may be of the order of a factor of 10. This approach compares an estimate with an estimate. This paper uses simulation to extend these studies by allowing a comparison to a ‘true match probability’ and supports the conclusion that subpopulation effects are mild. In addition the performance of recommendations 4.1 and 4.2 of NRC II [National Research Council and C.O.D.F. Science, The Evaluation of Forensic DNA Evidence, National Academy Press, Washington, DC, 1996].

Salt tolerance in Lycopersicon spp. VII. Pleiotropic action of genes controlling earliness on fruit yield

The change from vegetative to reproductive development (earliness) in Lycopersicon chesmannii line L2 was delayed for 20 weeks when compared to other Lycopersicon species under greenhouse conditions. The interspecific hybrid of L. chesmannii L2 and L. esculentum E9, a cherry tomato cultivar, also showed this delay in reproductive development. The distribution of this character in the F2-derived population showed a bimodal shape, plants could be scored easily as “early” or “late” in two nutrient conditions (optimum and high salinity). A QTL with major effects on earliness was detected in salinity, which explained 35.6% of the phenotypic variation. The effect of this QTL greatly diminished under control conditions, indicating differences in the genetic control of earliness between treatments. ACC synthase or phytochrome B2 are the products of candidate genes for such a major QTL. Other QTLs with minor effects, and epistatic interactions, are also involved in earliness under both conditions. A “late” F2 subpopulation yielded twice as much as an “early” F2; conversely, “early” plants were taller than “late” plants, regardless of the treatment. QTL analysis, carried out in both subpopulations, showed that yield differences may be explained by chesmannii alleles showing negative additive effects at some QTLs only in the “early” subpopulation. The effect of population subdivision on QTL analysis was investigated by computer simulations to show sample-size or random effects; thus, important pleiotropic or regulatory effects of genes controlling earliness on yield that affect QTL analysis, have been reveiled. Therefore alleles controlling earliness in L. chesmannii have to be taken into account for a more efficient utilization of the genetic resources of this species.

Developments in predicting the effective size of subdivided populations

The effective population size is the parameter that summarizes the magnitude of genetic drift and increase in inbreeding occurring in a population. In this paper, developments in the prediction equations for the effective size of populations subdivided under various models are reviewed, and extensions are made in several cases. Derivations are shown for some simple models, and the relationships among these equations and with those for a single unsubdivided population are discussed. The effect of population subdivision on neutral genetic variation and its implications are explained.

Waiting for Speciation: The Effect of Population Subdivision on the Time to Speciation

Waiting for Speciation: The Effect of Population Subdivision on the Time to Speciation

Effects of population subdivision and catastrophes on the persistence of a land snail metapopulation.

We modeled the dynamics of a metapopulation of the land snail Arianta arbustorum in north-eastern Switzerland to investigate the effect of population subdivision on the persistence of a land snail metapopulation and to analyze the interaction between spatial factors, population subdivision, and catastrophes. We developed a spatially structured, stochastic, age-structured metapopulation model with field data from previous studies on the metapopulation in Switzerland and experimental and meteorological data. The model incorporated distance-dependent dispersal through stream banks, correlated environmental fluctuations, and catastrophes resulting from heavy rains. The results point to various complex interactions among factors involved in metapopulation dynamics and suggest that in some cases population subdivision may act to decrease threats from environmental fluctuations and catastrophes.

DNA profile similarity in a subdivided population.

There is considerable debate regarding the effect of population subdivision (heterogeneity) on the probability of a chance or coincidental match between two DNA samples studied with respect to multiple, polymorphic genetic markers. We have theoretically investigated the relationship between the average similarity between two randomly chosen DNA samples and the probability of an identical match between these samples, and population subdivision. Our results demonstrate that the average similarity and the match probability is smaller when population heterogeneity exists as compared to a random mating population with identical gene frequencies, for realistic values of heterogeneity. In other words, ignoring subdivision provides numerical values only slightly larger than the true values and are, thus, conservative.

The effect of population subdivision on estimates of the likelihood ratio in criminal cases using single-locus DNA probes.

The interpretation of single-locus DNA profile evidence in criminal cases in normally performed using an assumption of independence of frequencies of alleles at different loci. The critical parameter is the probability of a suspect matching a criminal's DNA profile by change. Many authors have been concerned that the assumption of linkage equilibrium may be inaccurate and that the strength of evidence against suspects may be thereby exaggerated. Some have calculated the maximum size of this effect. What matters, however, is not the upper bound of what the true probability might be, but what the actual probability is in a subdivided population. By calculating this, one can show that the effect of population subdivision on the strength of DNA profile evidence is very minor.