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At least 919 records · Page 51Linked to original sources
PubMed1980

Canine blood groups. 1. Description of new erythrocyte specificities.

Methods of production and characterization of immune typing reagents reactive with the erythrocytes of the dog are described. Five of the reagents (agglutinins) were reactive with previously unknown blood group factors and were shown by statistical and genetic tests on 222 random samples and 28 families to belong to 5 previously unrecognized blood group systems. The five new systems were one-blood factor, two-allele, three-genotype systems like the B, C, D and F systems. These were arbitrarily named J, K, L, M and N.

Animals↗
PubMed1989

Testing for bimodality in frequency distributions of data suggesting polymorphisms of drug metabolism--histograms and probit plots.

1. The shape of histograms used to illustrate density distributions of indices of polymorphic drug metabolism was shown to be sensitive to the position of the cell divisions. 2. Non-linearity of the probit plot was shown not to indicate bimodality of the original density distribution. Computer simulation was used to generate examples of unimodal density distributions with curvilinear probit plots. 3. Using the same technique probit plots for bimodal density distributions were constructed. Some were shown to differ less from the probit plots of certain unimodal distributions than did the original density distributions. 4. The position of the antimode was shown not to coincide with inflections seen in the probit plots. 5. A new method for determining the linearity of probit plots is suggested.

Humans↗
PubMed1989

Testing for bimodality in frequency distributions of data suggesting polymorphisms of drug metabolism--hypothesis testing.

1. The theory of methods of hypothesis testing in relation to the detection of bimodality in density distributions is discussed. 2. Practical problems arising from these methods are outlined. 3. The power of three methods of hypothesis testing was compared using simulated data from bimodal distributions with varying separation between components. None of the methods could determine bimodality until the separation between components was 2 standard deviation units and could only do so reliably (greater than 90%) when the separation was as great as 4-6 standard deviation units. 4. The robustness of a parametric and a non-parametric method of hypothesis testing was compared using simulated unimodal distributions known to deviate markedly from normality. Both methods had a high frequency of falsely indicating bimodality with distributions where the components had markedly differing variances. 5. A further test of robustness using power transformation of data from a normal distribution showed that the algorithms could accurately determine unimodality only when the skew of the distribution was in the range 0-1.45.

Computers↗
PubMed2005

GST genotype may modify clinical phenotype in patients with Fanconi anaemia.

In the search for genetic modifiers of the Fanconi anaemia (FA) phenotype, we examined the role of polymorphism in three glutathione s-transferase genes (GSTT1, GSTM1 and GSTP1) in 356 FA patients enrolled in the International Fanconi Anaemia Registry (IFAR). Cellular sensitivity to 1,2:3,4 diepoxybutane was significantly increased in GSTT1 deleted compared with GSTT1 positive cases (median chromosomal breaks 11.1 vs. 8.3, P < 0.01) but there was no effect on clinical manifestations of FA. GSTM1 genotype significantly influenced time to bone marrow failure in complementation group FA-C, (median age 3.0 years vs. 7.0 years, P < 0.01). GSTP1 genotype did not influence FA phenotype.

Fanconi Anemia↗
PubMed2005

The peroxisome proliferator activated receptor gamma Pro12Ala polymorphism is associated with a lower hirsutism score and increased insulin sensitivity in women with polycystic ovary syndrome.

BACKGROUND: Polycystic ovary syndrome (PCOS) is characterized by hyperandrogenism and chronic anovulation. The genetic background of the insulin resistance frequently associated with PCOS is unclear. OBJECTIVES: To examine the influe nce of the Pro12Ala polymorphism of the peroxisome proliferator activated receptor gamma (PPARgamma), which is thought to play a role in the regulation of insulin sensitivity, on endocrine and metabolic parameters in PCOS patients. METHODS: PPARgamma alleles were analysed in 102 PCOS patients (age 27 +/- 5.3 years) and 104 age matched control women. PCOS was defined by the NIH-criteria as the presence of chronic oligo- or anovulation and hyperandrogenism. Family history and clinical parameters were evaluated by personal interview and physical examination, parameters of insulin resistance [homeostasis model assessment (HOMA) and Matsuda-index] were evaluated with a glucose tolerance test. RESULTS: Seventy-nine (77.5%) PCOS patients were carriers of the wild-type PPARgamma allele (Pro/Pro), while 23 (22.5%) had at least one Ala allele (X/Ala), with an equal distribution in controls. X/Ala PCOS women were more insulin-sensitive, evidenced by lower fasting insulin, HOMA index and insulin secretion. Differences in insulin resistance did not depend on body mass index. The genotype had no influence on lipid status, leptin, adiponectin, ghrelin, or family history of type 2 diabetes. A significantly lower proportion of Pro/Ala patients had hirsutism and they had on average lower hirsutism scores than Pro/Pro patients. No relationship was found between the Pro/Ala polymorphism and other signs of hyperandrogenism. CONCLUSION: The Pro12Ala polymorphism of the PPARgamma gene is associated with increased insulin sensitivity and lower hirsutism scores in PCOS women.

Adult↗
PubMed2005

How to use molecular marker data to measure evolutionary parameters in wild populations.

Estimating the genetic basis of phenotypic traits and the selection pressures acting on them are central to our understanding of the evolution and conservation of wild populations. However, obtaining such evolutionary-related parameters is not an easy task as it requires accurate information on both relatedness among individuals and their breeding success. Polymorphic molecular markers are very useful in estimating relatedness between individuals and parentage analyses are now extensively used in most taxa. The next step in the application of molecular data to wild populations is to use them to derive estimates of evolutionary-related parameters for quantitative traits, such as quantitative genetic parameters (e.g. heritability, genetic correlations) and measures of selection (e.g. selection gradients). Despite their great appeal and potential, the optimal use of molecular tools is still debated and it remains unclear how they should best be used to obtain reliable estimates of evolutionary parameters in the wild. Here, we review the methods available for estimating quantitative genetic and selection parameters and discuss their merits and shortcomings, to provide a tool that summarizes the potential uses of molecular data to obtain such parameters in wild populations.

Biological Evolution↗
PubMed2005

Evidence of selection for low cognate amino acid bias in amino acid biosynthetic enzymes.

If the enzymes responsible for biosynthesis of a given amino acid are repressed and the cognate amino acid pool suddenly depleted, then derepression of these enzymes and replenishment of the pool would be problematic, if the enzymes were largely composed of the cognate amino acid. In the proverbial "Catch 22", cells would lack the necessary enzymes to make the amino acid, and they would lack the necessary amino acid to make the needed enzymes. Based on this scenario, we hypothesize that evolution would lead to the selection of amino acid biosynthetic enzymes that have a relatively low content of their cognate amino acid. We call this the "cognate bias hypothesis". Here we test several implications of this hypothesis directly using data from the proteome of Escherichia coli. Several lines of evidence show that low cognate bias is evident in 15 of the 20 amino acid biosynthetic pathways. Comparison with closely related Salmonella typhimurium shows similar results. Comparison with more distantly related Bacillus subtilis shows general similarities as well as significant differences in the detailed profiles of cognate bias. Thus, selection for low cognate bias plays a significant role in shaping the amino acid composition for a large class of cellular proteins.

Amino Acids↗
PubMed1983

Family resemblance for fasting blood glucose in a population of Japanese Americans.

The pattern of inheritance of fasting blood glucose was examined in a Japanese cohort of 500 nuclear families living in Hawaii. A principal component of glucose was defined to improve the ranking of diabetics and individuals receiving treatment (medication and/or diet) for hyperglycemia, thereby allowing as well as possible for inability to determine untreated levels in patients. Results from path and segregation analysis show that family resemblance for glucose is low in this population. The additive variation can be explained by a cultural model of inheritance without introducing intergenerational differences, a maternal-paternal effect, or even genetic parameters. Heritability is approximately 0.125. Complex segregation analysis provides no convincing evidence for a major gene, with preliminary support based upon leptokurtic outliers in five families disappearing on further analysis by partial truncation. A claim by other workers of a major recessive gene for hyperglycemia may be due to their failure to allow for treatment, skewness, and multifactorial heritability. In future, the search for major loci acting on liability to hyperglycemia should use multiple determinations of fasting glucose or be addressed to more primary and repeatable variables than fasting blood glucose.

Adult↗
PubMed1984

Third order linkage disequilibrium.

For third order linkage disequilibrium there is a constraint on the maximum value the disequilibrium can take, given pairwise disequilibria values and allele frequencies. As distinct from second order disequilibrium (considered in the context of a two locus model) there is also in some cases a constraint on the minimum value. The appropriate procedures to determine these maximum and minimum values are given, as well as numerical values utilizing HLA data.

Alleles↗
PubMed2004

'Anti-bee' and 'pro-bird' changes during the evolution of hummingbird pollination in Penstemon flowers.

Floral phenotypes may be as much the result of selection for avoidance of some animal visitors as selection for improving the interaction with better pollinators. When specializing on hummingbird-pollination, Penstemon flowers may have evolved to improve the morphological fit between bird and flower, or to exclude less-efficient bees, or both. We hypothesized how such selection might work on four floral characters that affect the mechanics of pollen transfer: anther/stigma exsertion, presence of a lower corolla lip, width of the corolla tube, and angle of flower inclination. We surgically modified bee-pollinated P. strictus flowers changing one trait at a time to make them resemble hummingbird-pollinated P. barbatus flowers, and measured pollen transfer by bumblebees and hummingbirds. Results suggest that, apart from 'pro-bird' adaptations, specific 'anti-bee' adaptations have been important in shaping hummingbird-flowers. Moreover, some trait changes may have been selected for only if changing in concert with other traits.

Adaptation, Biological↗