M. Ray

A cytogenetic survey of 14,069 newborn infants. I. Incidence of chromosome abnormalities.

Data from a chromosome examination of 14,069 consecutive newborn infants is presented. Successful karyotypes were obtained on 13,939 babies using short‐term blood culture and conventional staining methods. Of those, 13,645 babies had normal chromosomes; 64 (0.46%) had a major chromosome abnormality; and 230 (1.65%) had a marker chromosome; giving a total of 294 (2.11%) babies with a major chromosome abnormality or distinctive marker chromosomes.

Familial mental retardation in a family with an inherited chromosome rearrangement

A family of three generations has been described with an insertional type of chromosome rearrangement involving chromosomes 11 and 18[46,XX or XY, ins(11;18)(p15;q11q21)] detected by G-banding using a trypsin digestion method. Four members of this family with clinical features of 18q− have inherited the der(18) from their father and are thus deficient for (18)(q11q21). Three other family members have inherited the der(11) and thus have a duplication of the same segment [(18)(q11q21)]. Genetic marker studies on this family, show no significant segregation of any of the markers studied with either the der(11) or der(18). Eight family members had the PepA8PepA1 genotype and four of these were carrying the der(18), indicating that the PepA locus which had been previously assigned to chromosome 18, does not lie in the segment q11→q21.

Phenotypic correlations in patients with ring chromosome 22

This paper reports two patients with a ring 22 chromosome which has been confirmed by Q‐banding. The literature contains 19 patients with a ring G‐group chromosome which has been shown by chromosome banding to be a ring 22. The most commonly reported features in affected patients have included: retardation with disproportionate verbal delay, reduced head circumference, hypotonia, unsteady gait, large ears with abnormal configuration, and epicanthic folds. The importance of these, as well as other, less often noted findings, is discussed in relation to a possible r(22) syndrome.

Homozygous Robertsonian translocations in a fetus with 44 chromosomes

SummaryWe report the unique finding of a human fetus with 44 chromosomes with homozygous 14;21 translocations. This fetus appeared phenotypically normal but the long-term neurodevelopmental outcome had this pregnancy continued could not be predicted. We speculate one 14;21 translocation was inherited from her father and one arose de novo being maternal in origin. A previous sibling with psychomotor retardation has an abnormal chromosome complement of 45,XX,dup(7)(q21→pter), t(14;21)(p11;q11). The mothers underlying disease, systemic lupus erythematosis (SLE), and her prior chemotherapy may have contributed to the appearance of these chromosome aberrations. It is interesting that although 14;21 translocations are among the commonest structural chromosome rearrangements in man, there are no previous reports in newborn surveys of a child with 44 chromosomes resulting from the mating of two identical Robertsonian translocation carrier parents.

Fragile 19p13 in a family with mental illness

We describe a family where four brothers show the rare heritable folate sensitive autosomal fragile site (FSAFS) at 19pl3 when cells were grown in TCI99. Two of the brothers are schizophrenic while one brother is mentally retarded with autistic‐like features. The clinical significance of this fragile site however is still unknown.

Deletion of the short arm of chromosome No. 10.

A newborn male infant, whose karyotype was 46,XY,del(10)(p13) is presented. The clinical features included cleft lip and palate, preauricular pits, low set malpositioned auricles, antimongoloid slant of the eyes, microcephaly, micrognathia, congenital heart disease, hypertrophic pyloric stenosis, cryptorchidism, and abnormal dermatoglyphics. The child died at the age of 3 months in overwhelming urinary infection with septicemic complications. It is suggested that the features described here may represent a new, clinically recognizable chromosomal syndrome.

Characteristics of an HPRT-deficient chinese hamster cell line.

A mutant Chinese hamster cell line was selected from wild-type CHW cells in 30 µg/ml 8-azaguanine, after exposure for 2 h to 10–3 M methyl methanesulphonate. This line was subsequently cloned and one clone, isolated in 10 µg/ml 8-azaguanine (CHW-1102), was selected for further study. CHW-1102 showed stability of resistance to 8-azaguanine after six months of growth in nonselective medium and an LD50 to 8-azaguanine of between 10 and 20 µg/ml, compared to 2.5 µg/ml for the wild-type CHW cell line. The doubling time in culture was found to be 13 h, compared to a doubling time of 12 h for CHW. Biochemical studies showed that the mutant cell line CHW-1102 had a specific activity of HPRT of about 1–2 nmol/mg protein per hour compared to a specific activity of the wild type of 200 nmol/mg protein per hour. The spontaneous reversion rate from 8-azaguanine resistance to 8-azaguanine sensitivity was 4.23 × 10–8/locus per generation. Both the parental line (CHW) and the mutant (CHW-1102) have a modal chromosome number of 22 and a relatively stable karyotype. Both lines show some chromosome rearrangement and, in particular, the presence of one long acrocentric marker chromosome, which consists largely of material from chromosomes 6 and 8. Much of the distal part of the long arm of the X chromosome, which is heterochromatic, has been lost in both CHW and CHW-1102. So far as can be determined, no autosomal material, except perhaps the paracentromeric region of chromosome 6, is missing in CHW-1102, although even this material may be represented by a small marker chromosome M2. Both cell lines show characteristics that are of value for the study of mammalian cell genetics, and CHW-1102 represents a useful addition to the stock of mutant mammalian cell lines.

Possible association of rare autosomal folate sensitive fragile sites and idiopathic mental retardation: a blind controlled population study

The expression of folate sensitive fragile sites (FS) was assessed in cord blood lymphocyte cultures obtained from 790 newborns (NB) and in peripheral blood lymphocyte cultures from 326 institutionalized mentally retarded residents (MR). The mean rate of expression of common FS and the occurrence of rare FS was significantly higher in the MR population. Age, sex and history of chronic medication use did not appear to influence common FS expression in the MR population. 3/790 (0.38%) NB and 5/326 (1.53%) MR exhibited rare autosomal folate sensitive FS, a 4‐fold difference in incidence (P = 0.009, Poisson test). Four of the five MR who expressed rare FS were considered to have idiopathic MR (4/179 or 2.2%). The occurrence of rare FS in 1/147 (0.68%) MR with known etiology is not significantly different from the frequency of occurrence in the NB population (P = 0.428, Poisson test). In this population, rare FS appear to be overrepresented in the idiopathic etiology MR group.

A 48,XXXX female

A four-year-old mildly retarded girl with a 48,XXXX karyotype is described. Her phenotype is compared to previously reported cases.