hybrid breakdown example liger

The breakdown of law and order saw southern Kyrgyzstan practically seceding from the rest of the country, with the northern region all but powerless to influence events in the Fergana Valley. MSM/Ms is a mouse strain derived from the Japanese wild mouse, Mus musculus molossinus. The severity of the abnormality increases from type 2 to type 6. var b=document.getElementsByTagName("script")[0]; Liger, offspring of a male lion and a female tiger. 1991). Histological analysis of the testes from the B6-XMSMY males of the N8 revealed ongoing spermatogenesis, but there were various degrees of degeneration in the seminiferous tubules (Figure 2). This contributes, in part, to the sterility of the B6-XMSMY males. (C and D) Spermatogenesis with moderate defects (C) and severe defects (D) was observed in the same B6-X MSM Y males. The magnification is ×5000 (D and E) or ×8000 (F). Hybrid … The sections (6 μm) were stained with hematoxylin and eosin. Hyperplasia of Leydig cells was observed in the interstitial space adjacent to the severely degenerated tubules (Figure 2B). 2002). —Histological analyses of testes and cauda epididymides. This reduction of fecundity of the hybrids prevents gene flow across the two different populations, accelerating genetic differentiation and eventually contributing to speciation. The use of the mouse consomic strains as a model system may shed light on genetic aspects of human infertility. Finally, we examined acrosome function of the B6-X MSM Y spermatozoa. Although lions and tigers may mate in the wild, they are separated by geography and behaviour, and thus all known ligers stem from accidental mating between lions and tigers as well as from directed breeding efforts that have occurred while in captivity. They enjoy swimming, which is a characteristic of tigers and are very sociable like lions. (C57BL/6J × MSM/Ms) F1 females were backcrossed to C57BL/6J males. Abnormally shaped nuclei were observed in the B6-XMSMY male (arrowhead). Genotyping of the X chromosome markers: The following MIT microsatellite markers, which differ between the C57BL/6J and the MSM/Ms strains, were monitored during the construction of the consomic strain: DXMit89, DXMit72, DXMit50, DXMit109, DXMit147, DXMit95, DXMit97, DXMit217, DXMit-249, and DXMit160, which are located at 3.0, 4.8, 14.1, 27.0, 33.5, 43.0, 49.0, 63.0, 70.5, and 73.3 cM, respectively, from the centromere. HYBRIDS between individuals of two genetically diverged populations show different extents of reproductive failure; this failure is known as reproductive isolation. Since no homologous recombination occurs through the whole X chromosome in XO females, this breeding scheme allowed introduction of the MSM/Ms-derived X chromosome as a whole into the C57BL/6J/CBA hybrid background. Because X-linked traits were analyzed in males, the dominance effect of a QTL could not be estimated. Hybrid breakdown may be due to disruption of interaction of genes at different loci as the genes segregate after the F1 generation. The first backcross generation is designated N2; subsequent backcross generations are designated N3, etc. Hybrid sterility has been observed in male offspring of crosses between different subspecies (Forejt and Ivanyi 1975; Forejtet al. The occurrence or the term of hybrid breakdown usually refers to at the F 2 or later generations. Observation was done under a transmission electron microscope at 75 kV accelerating voltage (H7100 type; Hitachi, Japan). Ligers are the offspring of a male lion bred with a female tiger. The genes of female lions, however, are adapted to cancel or dampen the effects of the growth-maximizing genes of male lions, so lions remain within a given size range. Our editors will review what you’ve submitted and determine whether to revise the article. The average testosterone level of the B6-XMSMY males of the N6 did not, however, differ from that of C57BL/6J and the B6-XB6Y males (C57BL/6J, 1.8 ng/ml ± 2.5, n = 5; B6-XB6Y, 1.0 ng/ml ± 1.7, n = 5; B6-XMSMY, 1.3 ng/ml ± 2.1, n = 5). So are mules, they're the product of a male donkey and a female horse. This research was supported in part by the “Genome Frontier Development Promotion” assisted by the Special Coordination Funds for Promoting and Science and Technology of the Ministry of Education, Culture, Sports, Science, and Technology of Japan and in part by grants in aid from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. Therefore, it is most likely that the morphological diversification is largely related to postmating isolation during the evolutionary process. This analysis successfully detected at least three distinct loci for the sperm head morphology and one for the testis weight. Get a Britannica Premium subscription and gain access to exclusive content. Observation with TEM revealed that epididymal spermatozoa of the B6-XB6Y males had regular, spindle-shaped sperm nuclei (Figure 3D). Identification of the Sha genes on the X chromosomes and of the interacting gene(s) located on autosomes and/or the Y chromosome would provide insight into this problem. The boundary of the pseudoautosomal region is located between DXMit249 and DXMit160 in the C57BL/6J strain (Perryet al. Enter multiple addresses on separate lines or separate them with commas. Background markers for composite interval mapping were chosen using the SRmapqtl module of QTL Cartographer. To quantify the severity of morphological defects, we gave points, 0-5, for types 1-6 and obtained a net score for individual males by adding up the percentage of their spermatozoa belonging to each type multiplied by the corresponding point value. The largest ligers often grow to lengths of more than 3.3 metres (10.8 feet) and weigh more than 400 kg (900 pounds); however, there are reports of some individuals weighing more than 1,000 kg (1 metric ton [about 2,200 pounds]). This hybrid sterility is likely caused by interallelic incompatibility at a given locus or at several different loci. Females with copulatory plugs were dissected to collect oocytes and/or embryos from the oviducts on the day after the copulation. …(sire) is a tiger and ligers when the sire is a lion.…, …a tigress is called a liger; that of a tiger and a lioness, a tigon; that of a leopard and a lioness,...…, Lion, (Panthera leo), large, powerfully built cat (family Felidae) that is second...…. Defects of spermatogenesis were observed in testes of some of the B6-XB6Y males, but in most cases the defect was much less severe than that in the B6-XMSMY males (data not shown). Seminiferous tubules with moderate defects were characterized by thin and fragile epithelia with reduced numbers of germ cells. Animals: The C57BL/6J strain was purchased in 1984 from the Jackson Laboratory (Bar Harbor, ME) and has been maintained in the animal facility at the National Institute of Genetics (NIG; Mishima, Japan). Previous mapping of the X-linked gene responsible for the hybrid breakdown identified Shx1, a locus 29 cM from the centromere, on the basis of a relatively small number of progeny of crosses involving XO females (Takagiet al. The results of the QTL analysis for spermatozoa morphology are summarized in Figure 5B. We constructed a congenic strain that carries the MSM/Ms-derived X chromosome in the interval of DXMit97-DXMit160 in the genetic background of the C57BL/6J strain. Dried spermatozoa were stained for 2 min with 0.22% Coomassie brilliant blue R250 (Fluka Chemie AG, Buchs, Switzerland) in 50% methanol/10% glacial acetic acid, rinsed with water, and mounted.

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