摘要:

Intraspecific variation in chromosome morphology is greater in two species of pocket gophers than within any other presently studied mammalian species. Diploid number varies only from 76 to 78. Therefore, the majority of the differences appear to be the results of pericentric inversions. These geographical chromosomal differences in Thomomys bottae and T. umbrinus are best explained as adaptations to habitat characteristics. Within both species, populations occurring in arid or shallow soil habitats have karyotypes characterized by a high number of acrocentrics, whereas populations in more favorable conditions have karyotypes composed entirely of metacentrics or submetacentric elements. These parallel trends suggest that the symmetry of the karyotype as a whole may have functional significance.

ISSN:1424-8581    

DOI:10.1159/000130121

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

The chromosomes of 14 species belonging to eight amphisbaenian genera are here reported. The karyotypes of nine species all comprise 6 pairs of metacentric macrochromosomes (M) and 7 to 12 pairs of microchromosomes (m). The M in these species are similar to one another in morphology. One species, Geocalamus acutus, has 7 pairs of M and 12 pairs of m; two of the M are telocentric, perhaps as a result of centric fission of one pair of metacentric M. The remaining four species, Bipes biporus, Amphisbaena alba, A. fuliginosa, and A. innocens, had higher diploid numbers and wide variations in morphology. B. biporus had 10 pairs of biarmed M and 11 pairs of m. A. alba had 11 pairs of M, 7 biarmed and 4 telocentric, and 8 pairs of m. A. fuliginosa had 11 pairs of M, only 3 biarmed and 8 telocentric, and 13 pairs of m. A. innocens also had 11 pairs of M, 4 biarmed and 7 telocentric, and 14 pairs of m. The karyotypes of these four species are so different from one another and from those of the remainder of the group that it was not possible to assess their cytogenetic relationships. A distinct and independent sequence of chromosomal evolution was presumably involved in each case. No heteromorphic pair or monosomy was observed in either male or female amphisbaenians.

ISSN:1424-8581    

DOI:10.1159/000130122

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

The advance of pachytene chromosome mapping as a practical method in human cytogenetic analysis has been hindered by preparations of insufficient quality. Slides suitable for chromomere mapping of pachytene chromosomes in the human male have been obtained with the use of an improved preparative method which incorporates hypotonic pretreatment in 0.125 m KC1 for 60 min at 37°C and the substitution of air-drying for squashing. These preparations meet the minimal requirements we propose: (1) accurately countable pachytene complements are present, and (2) patterns of discrete chromomeres are present late in pachytene. A further observation is that centromere positions of the autosomes are marked early in the pachytene stage by heavily compacted chromomeres; arm ratios derived on the basis of this assumption agree well with those of somatic metaphase chromosomes. The XY bivalent has not exhibited a comparable chromomere pattern, possibly because of its precocious compaction. Pachytene chromomere maps of normal bivalents provide a basis for higher resolution in the analysis of structural variation in the human chromosome complement

ISSN:1424-8581    

DOI:10.1159/000130123

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Provisional maps are given for the two smallest autosomes (chromosomes 21 and 22) at pachytene in the human male. The longer of the two consists of 10 chromomeres in a standard sequence of various sizes, and the shorter one of 6 such chromomeres, including in each case the large terminal chromomere within which the centromere is located. With increasing compaction many of the details of these chromomere patterns disappear. Nevertheless, the two bivalents remain distinguishable from each other by their having, in addition to the large terminal chromomere, three and two major markers, respectively. Maps are given both at the extended and compacted stages.

ISSN:1424-8581    

DOI:10.1159/000130124

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Analysis of pachytene chromosomes in testicular tissue of 11 subjects was conducted. A total of 158 acrocentric bivalents from group D and 50 from group G were studied. It was established that each of these five acrocentric bivalents showed a characteristic chromomere pattern, that is, number, size, shape, staining intensity, and tendency to aggregation versus disaggregation between adjacent or homologous chromomeres. Specificity of chromomere organization in acrocentric bivalents at the pachytene stage might provide a basis for their identification.

ISSN:1424-8581    

DOI:10.1159/000130125

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

A malformed girl presenting the typical clinical features of the cri-du-chat syndrome is described. Her karyotype contains three grossly abnormal chromosomes, a 5p–q+, a ring C and a 15q+. Formally, a minimum of six breaks is involved in the origin of this complex anomaly. Based on autoradiographic evidence, it is concluded that the cri-du-chat phenotype in this patient is due to a submicroscopical lesion in the distal segment of the short arm of the abnormal No. 5 chromosome; without noticeable loss of chromatin, a break involved in a pericentric inversion, 5p–q+ seems to have altered a chromosome section of crucial importance. Such an interpretation is supported by the reports of cri-du-chat cases with morphologically normal No. 5 chromosomes. The additional structural rearrangements in the child’s karyotype apparently did not affect his phenotype. Blood cultures from the child’s mother showed acentric fragments and ring chromosomes in 5.3% of 225 analyzed cells. Possible causes for this high aberration rate are di

ISSN:1424-8581    

DOI:10.1159/000130126

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Additional observations on a Robertsonian translocation segregating in the Saanen goat are reported. All of the animals born in this series of matings had balanced karyotypes, and all were phenotypically normal. Six translocation homozygotes were born, five females and one male. Three of the female homozygotes gave birth to phenotypically normal offspring. In five of seven twin pairs, both members of the pair had identical karyotypes with respect to the translocation chromosome and the sex chromosomes. The translocation chromosome was found more frequently among offspring born as singles, whereas the normal chromosome complement appeared more frequently among offspring born in multiple births. The data did not support the notion that this translocation possessed meiotic drive, either independently or in conjunction with the X or Y chromosome.

ISSN:1424-8581    

DOI:10.1159/000130127

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Polyploid spermatocytes were found in air-dried meiotic preparations of 8 of 10 adult males of the Djungarian hamster (Phodopus sungorus campbelli Thomas). Most of them were tetraploid spermatocytes I or diploid spermatocytes II, but cells of higher ploidy have also been found. It is argued that polyploid spermatocytes are not artifacts and that the most probable cause of their formation is fusion of cells at pachytene and soon after metaphase I.

ISSN:1424-8581    

DOI:10.1159/000130128

出版商:S. Karger AG    

年代:1971

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130129

出版商:S. Karger AG    

年代:1971

数据来源: Karger