^Ovo je kineski muntjak koji ima 46 hromozoma
^Ovo je indijski muntjak koji ima 6 hromozoma
Ako je promena broja hromozoma "major mutacija", objasni mi kako je ovaj kurac uspeo da promeni broj hromozoma 20 puta bez znatnih genetskih promena, a pritom su ostali sposobni za medjusobnu oplodnju. Dakle, ili je ceo prirodni poredak suspendovan, ili ti nešto nisi skontao. Hm...
The Indian muntjac possesses the lowest diploid chromosomal number in mammals (2n = 6 for females [F] and 7 for males [M]), whereas the Chinese muntjac has a 2n number of 46 in both sexes. These two species, however, can produce viable F1 hybrids (2n = 27) in captivity, and partial spermatogenesis was observed in hybrids. Other karyotyped species have intermediate numbers of chromosomes; for example, 2n = 8 F, 9 M in Muntiacus crinifrons, 2n = 8 F, 9 M in Muntiacus gongshanensis, and 2n = 13 F, 14 M in Muntiacus feae. The tufted deer, which is the sole species in the other genus of the Muntiacinae subfamily, has polymorphic karyotypes with three different diploid numbers, 46, 47, and 48, observed in natural populations.
A comparative study of karyotypes of muntjacs
We have used a combination of chromosome sorting, degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR), chromosome painting and digital image capturing and processing techniques for comparative chromosome analysis of members of the genus Muntiacus. Chromosome-specific paints from a female Indian muntjac were hybridised to the metaphase chromosomes of the Gongshan, Black, and Chinese muntjac by both single and three colour chromosome painting. Karyotypes and idiograms for the Indian, Gongshan, Black and Chinese muntjac were constructed, based on enhanced 4, 6-diamidino-2-phenylindole (DAPI) banding patterns. The hybridisation signal for each paint was assigned to specific bands or chromosomes for all of the above muntjac species. The interspecific chromosomal homology was demonstrated by the use of both enhanced DAPI banding and comparative chromosome painting. These results provide direct molecular cytogenetic evidence for the tandem fusion theory of the chromosome evolution of muntjac species.
Chromosomal evolution of the Chinese muntjac (Muntiacus reevesi).
The aim of this study was to test the validity of the hypothesis that the 2n=46 karyotype of the Chinese muntjac (Muntiacus reevesi) could have evolved through 12 tandem fusions from a 2n=70 hypothetical ancestral karyotype, which is still retained in Chinese water deer (Hydropotes inermis) and brown-brocket deer (Mazama gouazoubira). Combining fluorescence-activated chromosomal sorting and degenerate oligonucleotide-primed polymerase chain reaction, we generated chromosome-specific DNA paint probes for 13 M. gouazoubira chromosomes and most of the M. reevesi chromosomes with the exception of 18, 19 and X. These paint probes were used for fluorescence in situ hybridisation to chromosomal preparations of M. reevesi, H. inermis and M. gouazoubira. Chromosome-specific paint probes from M. reevesi chromosomes 1-5 and 11 each delineated more than one homologous pair (18 pairs in total) on the metaphases of H. inermis and M. gouazoubira. All the other probes from M. reevesi and probes from M. gouazoubira each hybridised to one pair of homologous chromosomes or regions. The C5 probe, derived from centromeric satellite sequences of M. reevesi, hybridised to the centromeric regions of all chromosomes of these three species. Most interestingly, several non-random interstitial signals, which are apparently localised to the putative fusion points, were found on chromosomes 1-5 and 11 of M. reevesi. Both the reciprocal painting patterns and localisation of the C5 probe demonstrate that M. reevesi chromosomes 1-5 and 11 could have evolved from 18 different ancestral chromosomes through 12 tandem fusions, thus providing direct molecular cytogenetic support for the tandem fusion hypothesis of karyotype evolution in M. reevesi.
A new centric fusion translocation in cattle: rob
A bull from Marchigiana breed (central Italy) was found to be a heterozygous carrier of a centric fusion translocation involving cattle chromosomes 13 and 19 according to RBA-banding and cattle standard nomenclatures. CBC-banding revealed the dicentric nature of this new translocation, underlining the recent origin of this fusion. In fact, both the bull's parents and relatives had normal karyotypes. In vitro fertilization tests were also performed in the bull carrying the new translocation, in two bulls with normal karyotypes (control) and in four other bulls carrying four different translocations.
Cytogenetics and reproduction of sheep with multiple centric fusions
The significance of centric fusions in domestic animals, with special reference to sheep, is reviewed. The mating is described of a further 856 ewes with either a normal chromosome number 2n = 54 or carrying one or more of the three different translocations (centric fusions) t1, t2 and t3 in various heterozygous and homozygous arrangements. Rams which were used in the matings were homozygous for one of the translocation chromosomes (2n = 52), double heterozygotes (2n = 52), triple heterozygotes (2n = 51) or were carriers of 4 translocation chromosomes (2n = 50) and 5 translocation chromosomes (2n = 49). A remarkably even distribution of segregation products was recorded in the progeny of all combinations of translocation ewes x translocation rams in those groups in which sufficient animals were available for statistical analysis. Forty-eight chromosomally different groups of animals were mated. Further, the overall fertility of the translocation sheep, measured by conception rate to first service, lambing percentage and number of ewes which did not breed a lamb, was not significantly different from New Zealand national sheep breeding data. In some groups the poorer reproductive performance could be explained by the age structure of the flock and inbreeding depression, which probably affected the performance of some animals. Sheep with progressively decreasing chromosome numbers, due to centric fusion, 2n = 50, 2n = 49 and 2n = 48, are reported. The 2n = 48 category represents a triple homozygous ewe and a triple homozygous ram and is the first report of the viable evolution of such domestic animals. Less than 1% of phenotypically abnormal lambs were recorded in a total of 1995 progeny born over 10 years. It is now considered that there is little or no evidence to suggest that centric fusions in a variety of combinations affect the total productive fitness of domestic sheep. It is suggested that future research should be more actively directed to understanding their genetic significance.
Induced Robertsonian fusions and tandem translocations in mammalian cell cultures
Cultures of a cattle cell line and a Peromyscus eremicus cell line recovering from a pulse-treatment with mitomycin C, actinomycin D, 33258 Hoechst, and nitrosoguanidine exhibited translocations between chromosomes at the centromeric regions (Robertsonian fusions) as well as between centromere and telomere and between telomeres (tandem translocations). The frequency of Robertsonian fusions was found to be dose-dependent and duration-dependent with the mitomycin treatment. Biarmed chromosomes resulting from fusions may be monocentric or dicentric. Analyses of clones isolated from treated cells suggested that fused chromosomes may perpetuate in the cell populations.
The Przewalski horse/domestic horse hybrid was fertile and showed normal spermatogenesis. Chromosome banding studies showed a close homology between the karyotypes of the Prezwalski horse (Equus przewalskii, 2n = 66) and the domestic horse (E. caballus, 2n = 64), and it is evident that a single Robertsonian translocation has occurred transforming four acrocentric chromosomes of E. przewalskii into two metacentric chromosomes in E. caballus. The investigations showed that a trivalent is formed at meiosis in the hybrid (2n = 65), segregation from which gives two classes of genetically balanced spermatozoa. Both of these are capable of producing normal offspring if they fertilize the eggs of a domestic mare.
I naravno, čovek http://learn.genetics.utah.edu/units/disor...obertsonian.cfm
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