Showing papers on "Chromosome 21 published in 1968"

Significance of sex chromosome derived heterochromatin in mammals.

Abstract: One mammalian X chromosome in females and the Y chromosome in males are heterochromatic, and they seem to carry “controlling centers” which affect both sex determination and various somatic characters. The euchromatic X chromosome may carry the structural genes for testicular as well as ovarian determination, the former only functioning in the presence of a Y chromosome or suitable autosomal modifier.

Chromosomal DNA synthesis in Drosophila melanogaster.

Abstract: Analysis of labeling patterns in three chromosome segments of Drosophila melanogaster has shown that the replicative activity within chromosomes is temporally ordered. Moreover, specific labeling patterns on one chromosome occur with specific patterns on another chromosome with a very high degree of correlation. This circumstance leads to the conclusion that DNA synthesis among all the regions in the three chromosome segments studied is coordinated. The various labeling patterns observed in any one chromosome and the combinations of labeling patterns observed in all three chromosome segments can be arranged in ordered arrays, if one assumes that the DNA synthesis in each chromosome region will go to completion without stopping once it has started. Such arrays can serve as models for the temporal order of DNA synthesis among chromosome regions. They predict that in any one chromosome DNA replication begins and ends at very few loci and that synthesis at a larger number of points occurs at an intermediate time.

Erythrocyte ATP: D -Fructose-6-phosphate I-Phosphotransferase (Phosphofructokinase) Activity in Children with Normal/ G Trisomic Mosaic Down's Syndrome and in Normal and Down's Syndrome Controls

Abstract: THERE is evidence to suggest that, in human subjects with mosaicism of cell lines normal and trisomic for chromosome 21, phenotypic expression is intermediate between that expected from each of the two cell lines. Moreover, the degree of expression of the trisomic cells (defined as the severity of clinical manifestations of Down's Syndrome (mongolism)) appears to be related to the proportion of trisomic cells1. In this study we investigated whether in tissues with normal/trisomy 21 mosaicism genetic biochemical expression was intermediate between that of the two individual cell lines.

An unusual karyotype in a patient with signs suggestive of Down's syndrome.

Abstract: _7. med. Genet. (1968). 5, 68. An Unusual Karyotype in a Patient with Signs Suggestive of Down’s Syndrome W. J. PEPLER, MOYRA SMITH, and W. A. VAN NIEKERK From the Departments of Physiology and Gynaecology of the University of Pretoria, Pretoria, South Africa It is now generally accepted that Down’s syn- drorne is due to the presence of extra genetic material of a chromosome in the G group. By con- vention, Down’s syndrome is attributed to the presence of a triple dose of the genetic material of chromosome 21, but recent autoradiographic studies seem to suggest that the extra chromosome is in fact No. 22 (Patau, 1965). However, for the sake of convenience the extra chromosome in this paper will be referred to as No. 21. Patients with the stigmata of Down’s syndrome are usually divided into two groups. The first group is comprised of those patients originally described by Lejeune, Gautier, and Turpin (1959) with a modal chromosome number of 47 and where the extra chromosome is indistinguishable from the autocentric autosomes in Group G. In the second group of patients only 46 chromosomes are present, the extra 21st chromosome being translocated onto another autosome. The translocation usually takes place onto another G or to a D chromosome. Another possibility in this group is the occurrence of an isochromosome of No. 21. The present paper describes a patient with features of Down’s syndrome, with a modal number of 47 chromosomes and in whom the extra chromo- some was found to be indistinguishable from the F group. Case Report The patient, a white female aged 41, has been an in- mate of the Weskoppies Mental Institution in Pretoria for many years. No personal or family history could be obtained and as far as could be ascertained the patient was born in South West Africa. On examination the skin was found to be dry and coarse and the hair straight and scanty. Her height was 140 cm. (4 ft. 7 in.) and the cranial circumference measured 48 cm. (19-25 in.). The face showed typical mongoloid features, with a small nose and chin, and the bridge of the nose was flattened (Fig. 1). The eyes were Received June l2_ I967. 68 small and narrow but there was no sign of any upward slope; the eyebrows, however, did show an upward lateral slope. There was no epicanthic fold, but well- marked strabismus could be seen. Bilateral cataract formation was present and as a result the vision was poor. In addition, severe conjunctivitis was present at the time of examination. The mouth was very small, and the tongue did not appear to be enlarged, but showed deep fissures. No arching of the palate could be seen. The ears were low-set and the pinnae much reduced in size. Hearing appeared to be normal. The neck was short and broad. The hands measured 13 cm. (5 in.) in length and H-3 cm. (4-5 in.) in breadth, and the thumb was far from the second finger, but there was no obvious shortening or inward curve of the fifth finger. The feet were short and broad with gross bunion formation. Examination of the nervous system proved to be very dificult as it was not possible to make contact with the patient. She was unable to help herself, but her poor vision was probably a contributing factor. No abnor- malities were detected on examination of the other systems. FIG. 1. I-‘acia of patient.

Transmission and phenotypic effect of a duplicate chromosome segment in maize.

Abstract: The chromosome B4, extracted from the translocation TB-4a (involving chromosome 4 and a B chromosome) was transferred into stocks with normal complement. This chromosome carried 75% of the short arm of chromosome 4 and was provided with a B centromere. Loss in somatic tissues, in meiotic divisions and through gametophyte competition in the pollen was investigated by cytological and genetical means. Nondisjunction in the second microspore division of the B4, in the presence of a normal chromosome 4, was not frequently observed. Sectoring in endosperm tissues, after appropriate crosses, presumably indicated either late replication of this chromosome and loss during endosperm development, and/or inactivation of the Su locus which is near the breakage point of the translocation with the B chromosome. Reduced vigor of the plants carrying one or two B4 chromosomes was interpreted as an effect of the duplication. There are indications that hyperploidy for this specific region may affect the kernel size and weight.

Familial D-E translocation.

Abstract: A familial D/E translocation is described. The proposita, a girl with features of the trisomy-E1 syndrome, had 47 chromosomes. The extra chromosome was a small acrocentric one. Her mother and little brother had 46 chromosomes, and showed a missing chromosome in the groups D and E, and an extra chromosome in the groups C and G. The former had a subterminal centromere. The latter could not be dinstinguished morphologically from the other small acrocentrics.

AnUnusual Karyotype inaPatient with Signs Suggestive ofDown's Syndrome

Abstract: FromtheDepartments ofPhysiology andGynaecology oftheUniversity ofPretoria, Pretoria, SouthAfrica Itisnowgenerally accepted thatDown'ssyndromeisduetothepresence ofextragenetic material ofachromosome intheG group.Byconvention, Down'ssyndrome isattributed tothe presence ofatriple doseofthegenetic material of chromosome 21,butrecentautoradiographic studies seemtosuggest thattheextra chromosome isinfact No.22(Patau, 1965).However, forthe sakeofconvenience theextrachromosome inthis paper will bereferred toasNo.21. Patients withthestigmata ofDown'ssyndrome areusually divided intotwogroups.Thefirst groupiscomprised ofthosepatients originally described byLejeune, Gautier, andTurpin(1959) withamodalchromosome numberof47andwhere theextra chromosome isindistinguishable fromthe autocentric autosomes inGroupG. Inthesecond groupofpatients only46chromosomes arepresent, theextra 21stchromosome being translocated onto another autosome. Thetranslocation usually takes place ontoanother G ortoa D chromosome. Another possibility inthis groupistheoccurrence ofanisochromosome ofNo.21. The present paperdescribes a patient with features ofDown's syndrome, withamodalnumber of47chromosomes andinwhomtheextra chromosomewasfoundtobeindistinguishable fromtheF