B-chromosomes

B-chromosomes

additional HETEROCHROMATIC CHROMOSOMES found in some ORGANISMS, over and above the normal number.
References in periodicals archive ?
Genetic characteristics of the B-chromosomes in maize.
Among plants B-chromosomes are mostly distributed in monocots.
Cytogenetic characterization of a supernumerary chromosome segment and of B-chromosomes in Astyanax scabripinnis (Teleostei, Characidae).
1989: B-chromosomes in two species of Indian weevils (Coleoptera: Curculionidae).
Sex differences in chiasmna frequency and distribution in natural populations of Eyprepocnemis plorans containing B-chromosomes.
In the latter species the chromosome number increases within and between populations due to the presence of a variable number of supernumerary chromosomes, from one to 18 B-chromosomes (Tsurusaki, 1993; Gorlov & Tsurusaki, 2000b).
There is, as expected, no evidence of homologies and translocation among these chromosomes and those that integrate the A complement, as one of the well-known characteristics of B-chromosomes is the absence of homology with the chromosomes of the normal complement (JONES, 1995).
The male transmission rate of B-chromosomes is controlled by the A-chromosomes in maize.
An unusual feature of Shiwasuaoba is its possession of several B-chromosomes (Jones, 1991).
The B-chromosomes in the wasp Nasonia, which are transmitted solely through sperm, are a representative case.
Among the major points of criticism are 1) the lack of relationship between the concept of homology in genome analysis and the "classical" concept of homology in morphology and molecular systematics; 2) the possible influence on chromosome pairing of specific genes, B-chromosomes, the environment, and so forth; 3) the magnitude and pattern of variation of chromosome pairing in hybrids; and 4) the problem of identifying pairing chromosomes during meiosis.