摘要:

Chromosome studies of six rodents, of which three have unusually large X chromosomes, and one lagomorph have been made. Two new methods of measuring unusually large sex chromosomes are presented. Compound sex elements are more often discovered as more species are studied, but the phenomenon in species without an X-to-autosome translocation is thus far restricted to the Artiodactyla, Rodentia, and Marsupialia, a point discussed in the text. Eutherian mammals known to have X chromosomes of more than 6 % of the haploid complement and all members of the Hystricomorpha that have been studied karyologically have been summarized.

ISSN:1424-8581    

DOI:10.1159/000130136

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Among the different species and spermatozoan types of the genus Drosophila there is immense variation in the whole length of the spermatozoon (ca. 55 to 15,000 µ) and in the length of its head (ca. 7.5 to 60µ). The width of the head and tail is of the order of 0.5 µ. There are either one, two, or three principal size classes of spermatozoa in every male, the number being species-specific. More than one size class in individual animals will be referred to as polymegaly. Both the head and flagellum exhibit a closely related polymegaly. The correlation between head and flagellum length within a size class is zero. According to the species, Drosophila spermatozoa in the testis are known to occur in bundles of, for example, 128 spermatozoa, each bundle derived from a single spermatogonium. Polymegaly is found to exist between but not within bundles. Polymegaly cannot, therefore, be due to meiotic segregation of factors affecting spermatozoan size. An hypothesis that polymegaly arises by omission of one or more of the successive waves of mitotic division during formation of the bundle is apparently untenable. In species with polymegaly, spermatozoa of a length intermediate between those of the size classes typical of the species are virtually never released from the testis. All size classes of spermatozoa are motile and reach the female genital tract but seem not to be randomly disposed between the female storage organs. Much of the variation between size classes both within and between species of the genus seems to reflect an harmonious underlying pattern of a restricted number of size modules that follow a geometric progression. The modular size or sizes would be determined by the genome of the species, perhaps also by the sex-chromosome complement in particular and by the rearing temperatu

ISSN:1424-8581    

DOI:10.1159/000130137

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

The affinity of the long arm of the Ychromosome for quinacrine dihydrochloride has been used in a study of size variation in this chromosome. Measurements made on cells from 12 subjects with Y chromosomes of different sizes have clearly indicated that it is variation in the fluorescent area which accounts for the size differences. The nonfluorescent region of the chromosome is apparently stable. The possible significance of these findings is discussed.

ISSN:1424-8581    

DOI:10.1159/000130138

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Morphological studies of mouse embryos (F1hybrids between inbred strains of CBA females and CBA-T6T6 males) on the 9th, 10th, and 11th day of development revealed a characteristic disturbance in embryogenesis, inhibited development of the embryonic part of the egg-cylinder. This disturbance first appeared on the 9th day but did not affect the fetal membranes, which retained their normal appearance until the 11th day. All the egg-cylinders characterized by this anomaly were triploid. The presence of only one T6 marker chromosome showed that triploidy occurred as a result of digyny.

ISSN:1424-8581    

DOI:10.1159/000130139

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

45, X/46, XYdic mosaicism in both skin and blood is reported in a six-year-old child presenting at birth with ambiguous genitalia. Examination revealed a greatly enlarged clitoris with perineal hypospadias, a small vagina, and bilateral inguinal hernias containing palpable gonads. Laparotomy and histology demonstrated a normal uterus and tubes with ovotestes in ovarian position. Physical examination was otherwise normal; she had the expected average height and weight for her age and no detectable aberrations of behavior. The dicentric Y chromosome was diagnosed on the basis of direct examination, autoradiography, and fluorescence analysis. Xg-blood grouping confirmed a single, maternally derived Xg locus. Search of suitable metaphases from short blood cultures revealed 104 cells with 46, XYdic; 26 with 45, X; 1 with 47, XYYdic; 2 with 46, XY; and 2 with 47, XYdicYdic. Findings in the skin indicated that the majority of cells were of the 45, X type. Examination of the patient’s blood cells during anaphase and telophase revealed more cells with bridge formation or lagging chromosomes than those from the normal controls. Such observation and the described karyotypes suggest that, although the dicentric Y usually divides normally during mitosis, in certain instances it divides abnormally to give XO and other aberrant cells. Possible mechanisms which may lead to such an unusual chromosome constitution are discusse

ISSN:1424-8581    

DOI:10.1159/000130140

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Arrighi and Hsu (1971) have described a method of differential staining of chromosomes based on the localization of repetitive DNA associated with heterochromatin. We have employed this method in an attempt to identify human chromosomes, especially the G group, Nos. 21 and 22 and the Y. Metaphases from a patient with 47,XY,21+ were examined. In addition to the Y chromosome, which shows dense staining in its long arm, three of the five G-group chromosomes show centromeric regions that stain much more densely than those of the other two. This indicates that it is possible to differentiate chromosome 21 from 22 and the Y. The possibility of identifying other chromosomes by similar differences is a likely one.

ISSN:1424-8581    

DOI:10.1159/000130141

出版商:S. Karger AG    

年代:1971

数据来源: Karger