Chromosome Heteromorphism

2017 ◽  
pp. 13-36
Author(s):  
Herman E. Wyandt ◽  
Golder N. Wilson ◽  
Vijay S. Tonk
Keyword(s):  
Chromosome Heteromorphism

Chromosome heteromorphism analysis in cases of disputed paternity

1983 ◽  
Vol 15 (1) ◽  
pp. 47-55 ◽  
Author(s):  
Susan B. Olson ◽  
R. Ellen Magenis ◽  
Shirley I. Rowe ◽  
Everett W. Lovrien ◽  
John M. Opitz
Keyword(s):  
Chromosome Heteromorphism

Karyotypes of side-necked turtles (Testudines: Pleurodira)

1980 ◽  
Vol 58 (5) ◽  
pp. 828-841 ◽  
Author(s):  
James J. Bull ◽  
John M. Legler
Keyword(s):  
Sex Chromosome ◽  
Ancestral Condition ◽  
Chromosome Heteromorphism

Karyotypes are presented for 13 of the 14 genera of side-necked turtles (suborder Pleurodira, families Pelomedusidae and Chelidae). Pelomedusids have low diploid numbers and few microchromosomes (2n = 26–36); the five largest chromosomes are homologous in the three genera. Chelids have high diploid numbers and many microchromosomes (2n = 50–64) and are similar in this respect to cryptodires (2n = 50–66). The pelomedusid karyotype is regarded as derived, probably from an ancestral condition like that seen in chelids. Gross karyotypic differences are slight or nil within genera and among closely related pleurodiran genera. Triploidy probably occurs in Platemys platycephala (family Chelidae) which has 96 chromosomes. No sex chromosome heteromorphism was observed.

Cytological evidence for population-specific sex chromosome heteromorphism in Palaearctic green toads (Amphibia, Anura)

2007 ◽  
Vol 32 (4) ◽  
pp. 763-768 ◽  
Author(s):  
G. Odierna ◽  
G. Aprea ◽  
T. Capriglione ◽  
S. Castellano ◽  
E. Balletto
Keyword(s):  
Sex Chromosome ◽  
Cytological Evidence ◽  
Chromosome Heteromorphism

Chromosome Heteromorphism (Summaries)

2017 ◽  
pp. 63-142
Author(s):  
Herman E. Wyandt ◽  
Golder N. Wilson ◽  
Vijay S. Tonk
Keyword(s):  
Chromosome Heteromorphism

Muller's Ratchet and the evolution of supernumerary chromosomes

Genome ◽  
1990 ◽  
Vol 33 (6) ◽  
pp. 818-824 ◽  
Author(s):  
David M. Green
Keyword(s):  
Genetic Information ◽  
Sex Chromosome ◽  
Chromosome Complement ◽  
Evolutionary Constraint ◽  
Supernumerary Chromosomes ◽  
Muller's Ratchet ◽  
Heteromorphic Sex Chromosomes ◽  
Muller’S Ratchet ◽  
Over Time ◽  
Chromosome Heteromorphism

Supernumerary chromosomes arise from portions of the normal chromosome complement through nondisjunction, fragmentation, or other mechanisms. Once present in the genome, they are subject to virtually the same genetic conditions that affect the evolutionary degeneration of heteromorphic sex chromosomes. Y or W chromosomes occur only in the presence of X or Z chromosomes, respectively, just as supernumeraries never occur except in the presence of the complete regular karyotype containing their progenitor sequences. Thus, mechanisms that can account for the evolution of sex-chromosome heteromorphism can also be invoked to explain the degeneration process of supernumerary chromosomes after their origination. Incipient supernumeraries initially have genes identical with those on progenitor chromosomes. This frees them from the evolutionary constraint of carrying nonduplicated genetic information, just as in Y and W chromosomes during early stages of sex-chromosome differentiation. The degeneration of supernumerary chromosomes may thus proceed via the mechanism of Muller's Ratchet. This hypothesis predicts that supernumerary chromosomes should lose functional loci, lose sequence homology with the regular genome, and gain heterochromatin over time, resulting in multiple heteromorphic forms of degenerate supernumeraries within and between populations, as is commonly observed.Key words: supernumerary chromosomes, B chromosomes, evolution, origin, Muller's Ratchet.

Intraindividual Y-chromosome heteromorphism

1985 ◽  
Vol 71 (3) ◽  
pp. 278-278 ◽  
Author(s):  
H. Hoehn ◽  
D. M. Kurnit
Keyword(s):  
Y Chromosome ◽  
Chromosome Heteromorphism

scholarly journals Karyotype characterization and ZZ/ZW sex chromosome heteromorphism in two species of the catfish genus Ancistrus Kner, 1854 (Siluriformes: Loricariidae) from the Amazon basin

2007 ◽  
Vol 5 (3) ◽  
pp. 301-306 ◽  
Author(s):  
Renildo R. de Oliveira ◽  
Eliana Feldberg ◽  
Maeda B. dos Anjos ◽  
Jansen Zuanon
Keyword(s):  
Sex Chromosomes ◽  
Amazon Basin ◽  
Sex Chromosome ◽  
Brazilian Amazon ◽  
Modal Number ◽  
Phylogenetic Relations ◽  
Karyotypic Formula ◽  
Pericentric Inversions ◽  
Acrocentric Chromosomes ◽  
Chromosome Heteromorphism

We present karyotypic characteristics and report on the occurrence of ZZ/ZW sex chromosomes in Ancistrus ranunculus (rio Xingu) and Ancistrus sp. "Piagaçu" (rio Purus), of the Brazilian Amazon. Ancistrus ranunculus has a modal number of 2n=48 chromosomes, a fundamental number (FN) of 82 for both sexes, and the karyotypic formula was 20m+8sm+6st+14a for males and 19m+9sm+6st+14a for females. Ancistrus sp. "Piagaçu" presented 2n=52 chromosomes, FN= 78 for males and FN= 79 for females. The karyotypic formula was 16m+8sm+2st+26a for males and 16m+9sm+2st+25a for females. The high number of acrocentric chromosomes in karyotype of Ancistrus sp. "Piagaçu" differs from the majority of Ancistrini genera studied so far, and may have resulted from pericentric inversions and translocations. The lower number of chromosomes in A. ranunculus indicates that centric fusions also occurred in the evolution of Ancistrus karyotypes. We conclude that karyotypic characteristics and the presence of sex chromosomes can constitute important cytotaxonomic markers to identify cryptic species of Ancistrus. However, sex chromosomes apparently arose independently within the genus and thus do not constitute a reliable character to analyze phylogenetic relations among Ancistrus species.

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