Genetic Change in Hatchery Populations

1993 ◽  
pp. 81-91 ◽  
Author(s):  
Graham A. E. Gall
Keyword(s):  
Genetic Change

scholarly journals Slow Genetic Divergence of Helicobacter pylori Strains during Long-Term Colonization

2005 ◽  
Vol 73 (8) ◽  
pp. 4818-4822 ◽  
Author(s):  
Annelie Lundin ◽  
Britta Björkholm ◽  
Ilya Kupershmidt ◽  
Magnus Unemo ◽  
Peter Nilsson ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Genetic Divergence ◽  
Bacterial Species ◽  
Pcr Amplification ◽  
Genetic Change ◽  
Genetic Changes ◽  
Single Strain ◽  
Divergent Gene ◽  
Asymptomatic Adult ◽  
H Pylori

ABSTRACT The genetic variability of Helicobacter pylori is known to be high compared to that of many other bacterial species. H. pylori is adapted to the human stomach, where it persists for decades, and adaptation to each host results in every individual harboring a distinctive bacterial population. Although clonal variants may exist within such a population, all isolates are generally genetically related and thus derived from a common ancestor. We sought to determine the rate of genetic change of H. pylori over 9 years in two asymptomatic adult patients. Arbitrary primed PCR confirmed the relatedness of individual subclones within a patient. Furthermore, sequencing of 10 loci (∼6,000 bp) in three subclones per time and patient revealed only two base pair changes among the subclones from patient I. All sequences were identical among the patient II subclones. However, PCR amplification of the highly divergent gene amiA revealed great variation in the size of the gene between the subclones within each patient. Thus, both patients harbored a single strain with clonal variants at both times. We also studied genetic changes in culture- and mouse-passaged strains, and under both conditions no genetic divergence was found. These results suggest that previous estimates of the rate of genetic change in H. pylori within an individual might be overestimates.

Models of Cultural and Genetic Change

1988 ◽  
pp. 61-80
Author(s):  
John Maynard Smith
Keyword(s):  
Genetic Change

GUDALI CATTLE OF WEST AND CENTRAL AFRICA

1996 ◽  
Vol 17 ◽  
pp. 147-164 ◽  
Author(s):  
C. L. Tawah ◽  
J. E. O. Rege
Keyword(s):  
Natural Selection ◽  
Production Systems ◽  
Central Africa ◽  
Genetic Change ◽  
East African ◽  
Pastoral Systems ◽  
Husbandry Practices ◽  
West And Central Africa ◽  
Conventional Literature ◽  
Available Information

SUMMARYThe objective of this paper was to compile the available information in the conventional and non-conventional literature on the origin, distribution, ecological settings, utility, husbandry practices and production systems of the Gudali, a West and Central African shorthorned zebu which is similar in conformation, size and origin to the East African shorthorned zebu. These animals are reputed not only for their beef and dairy qualities. but also for their hardiness to the harsh northerly environments. Under the prevailing circumstances in the pastoral systems, natural selection is the primary force affecting any genetic change and, as a result, animals tend to perform relatively poorly. Most of the documented studies have been limited in scope and applicability. Therefore, further studies are needed to adequately characterize these animals under their different production systems.

scholarly journals Temporal trends in probabilistic maturation reaction norms and growth of Atlantic cod (Gadus morhua) on the Icelandic shelf

2009 ◽  
Vol 66 (10) ◽  
pp. 1719-1733 ◽  
Author(s):  
Heidi Pardoe ◽  
Anssi Vainikka ◽  
Gudmundur Thórdarson ◽  
Gudrun Marteinsdóttir ◽  
Mikko Heino
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Temporal Trends ◽  
Age Groups ◽  
Reaction Norm ◽  
Genetic Change ◽  
Regional Survey ◽  
Fish Stocks ◽  
Abundance Estimates ◽  
Intensive Fishing

Decreasing temporal trends in probabilistic maturation reaction norm (PMRN) midpoints, symptomatic of earlier maturation despite environmentally induced variation in growth, have been observed in many exploited fish stocks. Here, we studied the growth and maturation trends of female and male Icelandic cod ( Gadus morhua ) by estimating PMRN midpoints for cohorts 1964–1999 and found evidence that a shift towards maturation at smaller sizes and younger ages has occurred independently of changes in growth, condition, and temperature. Weighting the data with regional survey abundance estimates to account for spatial heterogeneity in maturity status and sampling intensity did not qualitatively affect the temporal trends. Length-at-age also decreased through the study period, which, through simulations, could be attributed to the energetic costs of earlier maturity at maturing age groups but not at younger ages. These findings support the hypothesis that such changes in maturation schedules are not caused by environmental factors alone but could also reflect a genetic change, potentially in response to intensive fishing.

scholarly journals Polymorphic Inversion and Esterase Loci Complex on Chromosome 2 of Drosophila buzzatii. I. Linkage Disequilibria

1987 ◽  
Vol 40 (3) ◽  
pp. 257 ◽  
Author(s):  
WR Knibb ◽  
PD East ◽  
JSF Barker
Keyword(s):  
New World ◽  
Genetic Change ◽  
Chromosome 2 ◽  
Population Bottlenecks ◽  
Linkage Disequilibria ◽  
Drosophila Buzzatii ◽  
Conditional Allele ◽  
Esterase Loci ◽  
Almost All ◽  
Significant Linkage

Chromosome 2 inversion, Est-l and Est-2 haplotype frequencies were determined for 19 wild D. buzzatii collections from the known range of this species in Australia. Three different chromosome 2 sequences (ST, j, j z3) were polymorphic across the collections. They occurred at overall frequencies which approximated those in the ancestral New World and colonized Old World populations, which indicated that no radical genetic change was associated with the colonization of Australia by D. buzzatii. Linkage disequilibria of Est-l and Est-2 alleles with the inversions tended to be strong, and consistent in direction, in almost all collections. The distributions of conditional allele frequencies within the different inversions were consistent with stochastic historical explanations for the linkage disequilibria. Significant linkage disequilibria between Est-l and Est-2 were evident after correcting for the inversions, but these disequilibria largely were restricted to southern (higher latitude) populations, and were inconsistent in direction among the collections. Hence, population bottlenecks may underlie these genic disequilibria.

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