So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

The great increase in successful linkage studies in a number of higher eukaryotes during recent years has essentially resulted from major improvements in reference genetic linkage maps, which at present consist of short tandem repeat polymorphisms of simple sequences or microsatellites. We report here the last version of the Genethon human linkage map. This map consists of 5,264 short tandem (AC/TG)n repeat polymorphisms with a mean heterozygosity of 70%. The map spans a sex-averaged genetic distance of 3,699 cM and comprises 2,335 positions, of which 2,032 could be ordered with an odds ratio of at least 1,000:1 against alternative orders. The average interval size is 1.6 cM; 59% of the map is covered by intervals of 2 cM at most and 1% remains in intervals above 10 cM.

A comprehensive genetic map of the human genome based on 5,264 microsatellites

Lipids and their constituent fatty acids are, along with proteins, the major organic constituents of fish, and they play major roles as sources of metabolic energy for growth including reproduction and movement, including migration. Furthermore, the fatty acids of fish lipids are rich in ω3 long chain, highly unsaturated fatty acids (n-3 HUFA) that have particularly important roles in animal nutrition, including fish and human nutrition, reflecting their roles in critical physiological processes. Indeed, fish are the most important food source of these vital nutrients for man. Thus, the longstanding interest in fish lipids stems from their abundance and their uniqueness. This review attempts to summarize our present state of knowledge of various aspects of the basic biochemistry, metabolism, and functions of fatty acids, and the lipids they constitute part of, in fish, seeking where possible to relate that understanding as much to fish in their natural environment as to farmed fish. In doing so, it highli...

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Metabolism and Functions of Lipids and Fatty Acids in Teleost Fish

Since the 1970s, the spread of multidrug-resistant (MDR) Acinetobacter strains among critically ill, hospitalized patients, and subsequent epidemics, have become an increasing cause of concern. Reports of community-acquired Acinetobacter infections have also increased over the past decade. A recent manifestation of MDR Acinetobacter that has attracted public attention is its association with infections in severely injured soldiers. Here, we present an overview of the current knowledge of the genus Acinetobacter, with the emphasis on the clinically most important species, Acinetobacter baumannii.

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An increasing threat in hospitals: multidrug-resistant Acinetobacter baumannii.

Unsustainable fishing practices have placed a heavy emphasis on aquaculture to meet the global shortfalls in the supply of fish and seafood, which are commonly accepted as the primary source of health-promoting essential omega-3 (n-3 highly unsaturated fatty acids). However, dietary fish oil is required for the production of omega-3-rich farmed fish and this commodity, in a vicious circle, is at present derived solely from wild fisheries. Decreasing global availability coupled with the highly variable price of this resource has forced the aquaculture industry to investigate the possibilities of alternative dietary lipid sources. This review attempts to compile all principal information available regarding the effects of fish oil replacement for the diets of farmed finfish, analysing the findings using a comparative approach among different cultured fish species. The review initially focuses on the present situation with regard to the production, availability and main nutritional characteristics of fish oil and the principal alternative lipid sources (such as vegetable oils and animal fats). Following this, the effects of fish oil replacement in finfish nutrition on feed quality, fish performance, feed efficiency, fish lipid metabolism, final eating quality and related economic aspects are presented and discussed.

Fish oil replacement in finfish nutrition

Genetic basis of trypanotolerance in cattle and mice.

A study of polymorphisms of mitochondrial DNA (mtDNA) of West African N'Dama (Bos taurus) and East African Zebu (B. indicus) cattle was carried out to obtain information on maternal phylogenetic relationships between these breeds. A relatively large sample size was made possible by using polymerase chain reaction (PCR) amplification of DNA prepared from small blood samples to generate fragments of two known polymorphic mtDNA regions, one within the gene encoding subunit 5 of NADH dehydrogenase and one encompassing the entire D-loop. This approach allowed us to achieve a higher resolution restriction analysis on mtDNA from more animals than would have been possible by conventional methods. PCR-amplified mtDNA of 58 animals from five populations was examined at 26 restriction sites by 16 enzymes. In this way 154 nucleotides of mtDNA were scanned for polymorphism. Six polymorphic sites were located by this means, five of which were within the D-loop and one of which was within the NADH dehydrogenase 5 gene. None of the polymorphisms observed could be considered typical of breed or type.

Polymerase chain reaction analysis of mitochondrial DNA polymorphism in N'Dama and Zebu cattle.

To optimize designs to implement marker-assisted introgression programs aiming to introgress three unlinked quantitative trait loci (QTL), the present paper studies different alternatives versus a traditional backcross or intercross phase. Four alternative backcross strategies appear to be more advantageous by having 50% less genotyping load than a traditional backcross strategy tracking all three QTL at a time through a single line. A multiplication phase following the selection of homozygous animals at the three QTL as an intercross alternative allows doubling of the number of homozygous animals in a mouse model compared with the first intercross generation. Within the same model, a second intercross alternative with individuals carrying all three QTL at the first intercross results in a 12-fold increase in the number of homozygous animals obtained in the first intercross generation. The same ranges of decrease are observed in the number of animals to be genotyped and the number of genotypings when targeting a fixed number of homozygous animals. An option, with two lines each carrying two QTL through the backcross phase and coupled with the second intercross alternative, appears to be the best introgression alternative. This option requires 76% fewer genotypings, 68% fewer animals to be genotyped, and costs 75% less than an option in which all three QTL are introgressed through a single line.

Strategies to optimize marker-assisted introgression of multiple unlinked QTL.

A polymorphic Y chromosome microsatellite locus in cattle

Summary. It has hitherto proved difficult to phenotype cattle for class II histocompatibility antigens using standard serological techniques because of problems of reagent specificity and antigen expression on peripheral blood mononuclear cells (PBMs). We recently described the production of class II-specific alloreactive bovine T cell clones characterized by the BoT4+ phenotype. In this report we describe studies of the application of four such clones, derived from a single mixed leucocyte culture (MLC), for class II phenotyping in proliferation and cytotoxicity assay systems. Proliferation assays used irradiated PBM as stimulator cells and cytotoxicity assays used Theileria parva-infected lymphoblastoid cells as targets. Proliferation assays revealed three distinct specificities among the four clones indicating that they detected three different class II determinants. Furthermore, in a family study, the genes encoding the determinants recognized by the clones were found to be linked to the gene encoding the w10 class I A locus product on one of the w10-bearing haplotypes in our study population. Two of the clones were studied in cytolysis assays. Lack of cytolysis of one of the targets, which was derived from the PBM of an animal carrying a class II determinant detected in proliferation assay, was explained by the total lack of expression of class II antigens on the target cell line in question, as determined with 4 class II-specific monoclonal antibodies (mAb). We conclude that BoT4+ alloreactive clones provide a potentially useful and particularly discriminating way of detecting polymorphic class II antigens of cattle, especially when applied in assays of proliferative response to PBM.

Alan J. Teale

Papers

Genetic basis of trypanotolerance in cattle and mice.

Polymerase chain reaction analysis of mitochondrial DNA polymorphism in N'Dama and Zebu cattle.

Strategies to optimize marker-assisted introgression of multiple unlinked QTL.

A polymorphic Y chromosome microsatellite locus in cattle

A study of BoLA class II antigens with BoT4+ T lymphocyte clones.