Biomedical subjects

M Trick

Publications and source records attributed to M Trick.

21 records · Page 2Linked to original sources

PubMed1984

Unexpectedly slow homogenisation within a repetitive DNA family shared between two subspecies of tsetse fly.

Repetitive DNA families in sexual species are subject to a variety of turnover mechanisms capable of homogenising newly arising mutations. Very high levels of homogeneity in DNA families in some species of Drosophila indicate that the rate of turnover is fast relative to that of mutation. To gauge the generality of such phenomena, we cloned and sequenced individual members of homologous repetitive DNA families from two subspecies of tsetse fly, Glossina morsitans centralis and G. morsitans morsitans. Unexpectedly high levels of variation were found within each subspecies, averaging 24% and 31%, respectively. Contiguous repeats and repeats cloned at random were comparably divergent. Nevertheless, it was possible to identify three instances of apparent homogenisation, each being, remarkably, of an insertion/deletion nature. We conclude that the rate of turnover in the tsetse families is comparable to that of most mutations, and discuss the possible parameters affecting flux in these families.

Animals↗

PubMed1984

Genetic relationships between subspecies of the tsetse fly Glossina morsitans inferred from variation in mitochondrial DNA sequences.

A 750 base pair segment of DNA from the tsetse fly Glossina morsitans morsitans was isolated by means of molecular cloning. It was shown by DNA hybridization to have substantial sequence homology with a defined region of the mitochondrial genomes of several Drosophila species. When used as a probe against DNA prepared from single tsetse flies, the cloned sequence revealed local restriction site variation between members of the G. morsitans subspecies complex. This feature was used to demonstrate maternal inheritance of the sequence in progeny of hybrid crosses and to assemble comparative restriction maps for a 3-kilobase segment of each mitochondrial genome. The data obtained from these exercises point to a higher genetic identity between G. m. morsitans and G. m. centralis than between either form and G. m. submorsitans.

Animals↗

PubMedDate not supplied

Cryptic simplicity in DNA is a major source of genetic variation.

DNA regions which are composed of a single or relatively few short sequence motifs usually in tandem ('pure simple sequences') have been reported in the genomes of diverse species, and have been implicated in a range of functions including gene regulation, signals for gene conversion and recombination, and the replication of telomeres. They are thought to accumulate by DNA slippage and mispairing during replication and recombination or extension of single-strand ends. In order to systematize the range of DNA simplicity and the genetic nature of the regions that are simple, we have undertaken an extensive computer search of the DNA sequence library of the European Molecular Biology Laboratory (EMBL). We show here that nearly all possible simple motifs occur 5-10 times more frequently than equivalent random motifs. Furthermore, a new computer algorithm reveals the widespread occurrence of significantly high levels of a new type of 'cryptic simplicity' in both coding and noncoding DNA. Cryptically simple regions are biased in nucleotide composition and consist of scrambled arrangements of repetitive motifs which differ within and between species. The universal existence of DNA simplicity from monotonous arrays of single motifs to variable permutations of relatively short-lived motifs suggests that ubiquitous slippage-like mechanisms are a major source of genetic variation in all regions of the genome, not predictable by the classical mutation process.

Animals↗