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At least 37 records · Page 2Linked to original sources
PubMed1986

Origin of eukaryotic introns: a hypothesis, based on codon distribution statistics in genes, and its implications.

A hypothesis for the origin of introns in eukaryotic genes is developed. By computer simulation it was found that the reading-frame lengths in a random nucleotide sequence are distributed in a negative exponential manner and that there exists an upper limit of about 200 codons in the length of the reading frames (RFs). These characteristics suggest that, if primordial DNA contained a random nucleotide sequence, the most primitive cells would have been under selective pressure to eliminate interfering stop codons in order to increase the length of RFs. Further, they indicate that the only possible way that a coding sequence that is considerably longer than 600 nucleotides could be derived from the short coding sequences occurring in a random sequence would be to splice the short coding sequences and to eliminate the stretches of sequences containing clusters of inframe stop codons. Thus, introns are suggested to be those stretches of sequences containing interfering stop codons that were originally earmarked in the first primitive cells to be eliminated in order to enable the coding for long polypeptides. Because the statistical characteristics of codon distributions in today's eukaryotic DNA sequences resemble closely those of a random sequence and because the upper limit in the length of RFs (200 codons) in a random sequence corresponds precisely to the observed maximum length of exons in today's eukaryotic genes (600 nucleotides), it is suggested that introns originated in the most primitive unicellular eukaryotes when they evolved from primordial sequences. The data from the prokaryotic gene sequences indicate that prokaryotic genes may have been derived originally from primitive unicellular eukaryotic genes by losing introns from them.

Animals↗
PubMed1990

Truth and consequences of ordinal differences in statistical distributions: toward a theory of hierarchical inference.

A theory is presented that establishes a dominance hierarchy of potential distinctions (order relations) between two distributions. It is proposed that it is worthwhile for researchers to ascertain the strongest possible distinction, because all weaker distinctions are logically implied. Implications of the theory for hypothesis testing, theory construction, and scales of measurement are considered. Open problems for future research are outlined.

Humans↗
PubMed1985

The statistical distribution of nucleic acid similarities.

All pairs of a large set of known vertebrate DNA sequences were searched by computer for most similar segments. Analysis of this data shows that the computed similarity scores are distributed proportionally to the logarithm of the product of the lengths of the sequences involved. This distribution is closely related to recent results of Erdos and others on the longest run of heads in coin tossing. A simple rule is derived for determination of statistical significance of the similarity scores and to assist in relating statistical and biological significance.

Base Sequence↗
PubMed1977

The statistical distribution of macrophage migration distance and its application to MIF test.

The measurement of the distance of macrophage migration is very simple and reasonable as a technique in MIF assay. By the use of this technique, a large scale model experiment was performed and its data were analysed statistically. As the result of analysis, Student's t-test for significance of the difference between control and test readings of migration distance at low activity level in the MIF test was justified, and it was proved that it is applicable to the routine MIF test. In addition to this, the measurement of migration distance was compared with that of migration area.

Animals↗
PubMed1998

Statistical distribution of factors and factor images in factor analysis of medical image sequences.

From a time or energy image sequence, factor analysis of medical image sequences (FAMIS) estimates factors, representing kinetics or spectra in a given physiological compartment, and associated factor images, showing the compartments corresponding to each curve. In this paper, we show that the statistical properties of factor images and associated factors can be determined using a well known result from elementary probability theory. Numerical experiments are conducted to demonstrate that the variance observed in factor images can be predicted when the statistical properties of the original data are known. It is shown how these theoretical results can be used to relax the non-negativity constraints during FAMIS oblique analysis and to improve the quantitative interpretation of the factor images by associating a confidence interval with each pixel value.

Biophysical Phenomena↗
PubMedDate not supplied

[Weibull statistical distribution in physiologic research].

An attempt is made to define more precisely the law of arterial pressure incidence rate in population of normal subjects and patients suffering from different diseases. The incidence rate is found to obey the Weibull three-parameter law.

Adolescent↗
PubMedDate not supplied

Determination of depletion and statistical distribution of morantel-related residues in bovine milk following administration of morantel tartrate to dairy cows.

Residue depletion studies were conducted in dairy cattle to monitor morantel-related residues in milk following oral administration of morantel tartrate (Rumate. Eleven lactating cows of various ages, periods of lactation, and known milk production were orally dosed with the bolus formulation of morantel tartrate with an actual dose range of 8.4-9.8 mg/kg body weight. Representative samples of milk were collected at 10-14 h intervals post-dose, and subsamples were assayed for the major and minor hydrolysis products of morantel-related residues, MAPA and CP-20,107. Residues assayed as precursors of MAPA peaked at the second milking (24 h post-dose) and were below 25 ppb (range: less than 12-24 ppb). Precursors of CP-20,107, which confirm the identity of morantel, also peaked at 24 h post-dose (range: 2.1-3.3 ppb) and declined rapidly thereafter. A statistical model was used to project the level of residues at the upper limit of 99% of the total target animal (i.e., dairy cattle) population with 95% confidence. The calculated peak levels from this model were 50 and 5.0 ppb for morantel-related residues convertible to MAPA and CP-20,107, respectively.

Animals↗
PubMed1995

On the statistical distribution of amino acid residue in randomly synthesized peptides.

The probability of randomly synthesized peptides having an excess of a given residue Ri (nRi > N/2; N = size of the peptide) decreases strongly with peptide size. For a strong specific interaction of a Ri, rich peptide with a given sequence of a ribotide chain, peptides should be reasonably large. We discuss how a compromise can be achieved that may have had an important role on the origin of the genetic code.

Amino Acids↗