Backcrosses

Fig. 3. Fruit yields at various salinities (FW, freshwater SW, seawater) of Lycopersicon esculentum cv. Walter, and the Fj and backcross (FjBC,) resulting from its hybridisation with L. cheesmanii. Data of Rush Epstein (1981).

The entire genus has undergone much hybridization and backcrossing. Botanists have a difficult time differentiating all the different varieties because of this. 

Beebe, A.M., Mauze, S., Schork, N.J. and Coffman, R.L. (1997) Serial backcross mapping of multiple loci associated with resistance to Leishmania majorin mice. Immunity 6, 551-557. 

Gerlai 1996,2001). In such cases, animals have to be crossed with a pure inbred strain (commonly C57BL/6J hnes) for at least 6-8 generations (backcrossing). For correct interpretation of data obtained in genetically modified mice it is indispensable to follow the strict rules of strain nomenclature (Wotjak 2003). 

Gavrilenko, T. T., Ramona, Heimbach, U., Thieme, T. (2003). Fertile somatic hybrids of Solanum etuberosum (+) dihaploid Solanum tuberosum and their backcrossing progrenies relationships of genome dosage with tuber development and resistance to potato virus Y. Euphytica 131, 323-332. 

Sanford, L. L., Deahl, K. L., Sinden, S. L., Kobayashi, R. S. (1995). Glyeoalkaloid content in tubers of hybrid and backcross populations from a Solanum tuberosum x S. chacoense cross. American Potato Journal, 72,261-271. 

The 100% incidence in the large bowel of Fj and susceptible backcross hybrids indicated dominance of the ICR-derived susceptibility to carcinogenesis by 1,2-dimethylhydrazine. Findings in the F2 and resistant backcross hybrids are mutually supportive and in agreement with the respective 75% and 50% tumour incidences expected if a single dominant susceptibility gene is inherited from the ICR grandparent (Evans et al., 1977). 

Hybrid crosses were bred from a highly sensitive strain SWR/J mice and AKR/J mice highly resistant to 1,2-dimethylhydrazine carcinogenesis. 1,2-Dimethylhydrazine was injected subcutaneously at a dose of 20 mg/kg bw weekly with a total of 10 injections. Mice were killed 27 weeks after the first injection of 1,2-dimethylhydrazine. The colon tumour incidence in the hybrids and backcrosses is given in Table 15. The interpretation of results by the authors was that susceptibility to 1,2-dimethylhydrazine-induced tumorigenesis is not inherited as a dominant trait and that the kinetic properties of the epithelial cells are not linked to 1,2-dimethylhydrazine susceptibility (Deschner et al, 1988). 

Deschner, E.E., Long, EC. Hakissian, M. (1988) Susceptibility to 1,2-dimethylhydrazine-induced colonic tumors and epithelial cell proliferation characteristics of FI, F2, and reciprocal backcrosses derived from SWR/J and AKR/J parental mouse strains. Cancer, 61, 478-482... 

Ah locus A gene(s) controlling the trait of responsiveness for induction of enzymes by aromatic hydrocarbons. In addition to aromatic hydrocarbons such as the polycyclics, the chlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls, as well as the brominated biphenyls, are involved. This trait, originally defined by studies of induction of hepatic aryl hydrocarbon hydroxylase activity following 3-methylcholanthrene treatment, is inherited by simple autosomal dominance in crosses and backcrosses between C57BL/6 (Ah-responsive) and DBA/2 (Ah-nonresponsive) mice. 

McCloskey, W.B. and J.S. Holt (1990). Triazine resistance in Senecio vulgaris parental and nearly-isonuclear backcrossed biotypes is correlated with reduced productivity. Plant Physiol. 92 954—962. 

In spite of the strong evidence just cited, lupus nephritis is not invariably correlated with serum anti-dsDNA. (NZB x NZWjFi x NZW backcross mice may develop nephritis without anti-DNA antibodies (Y5). Patients with lupus nephritis also do not always have anti-dsDNA antibodies or have only low levels of antibodies (A23, H7, L21). Swaak et al. noted a sharp drop at the time of flareup of anti-dsDNA antibodies accompanied by low levels of Clq and C3 in patients with severe SLE flares (S36). 

Otsu K, Khanna VK, Archibald AL, MacLennan DH. Cosegregation of porcine malignant hyperthermia and a probable causal mutation in the skeletal muscle ryanodine receptor gene in backcross families. Genomics 1991 11(3) 744-750. 

TEM-l /3-lactamase 3 cycles of shuffling and 2 cycles of backcrossing, 32,000-fold increase in antibiotic resistance Stemmer, 1994... 

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