Biomedical subjects
Publications and source records attributed to M Fraccaro.
A healthy, 10-year-old male born in Milano to a family from Southern Italy (Puglia) was found to be a homozygote for an albumin variant of the fast type. His parents are half-first cousins. Their common grandfather, the parents, one sister, and three brothers of the child were all heterozygotes for the same albumin variant. This seems to be the first case of a homozygote for a fast albumin variant described in Europe.
Gene dosage effect for the enzyme peptidase A was studied in the red cells of subjects trisomic (seven cases) or monosomic (five cases) for the segment of chromosome 18 carrying the gene. The individual levels of enzyme activity in both groups were differen from those of the controls, but with a wide overlap. The use of the ratio of the activity of each subject to the midparent activity eliminated the overlapping. The mean ratio was 0.94 for the controls, 2.36 for the trisomics, and 0.41 for the monosomics. The trisomic ratio is higher than expected on the assumption of a linear effect. Correlation with the cytogenetic data in four cases of ring 18 and one of 18q- firmly places the gene for peptidase A on band 18q23.
The restriction endonuclease BSu, an isoschizomer of the enzyme HaeIII, cleaves human DNA to yield classes of fragments that are characteristic of the DNA of individuals having a Y chromosome. The fragments concerned are therefore diagnostic of the presence of Y-chromosome DNA and have been studied here with the intention of confirming the origin of various translocations thought, on other grounds, to involve the Y. The absence of the fragments from DNA of a case exhibiting absence of the fluorecent region of Yq suggests that the DNA concerned maps predominantly to Yq. Normal gender in the absence of the BSu fragments indicates that they do not function in sex determination.
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A woman balanced carrier of a X/15 translocation gave birth to a balanced infertile son and three unbalanced Xp--fertile daughters. This family and the other eleven cases of Xp--fertile women found in the literature demonstrate that loss of the p21 leads to pter region of the X chromosome is compatible with fertility, probably because it leaves on Xp the region which is never inactivated.
A child with female hypospadia complicated by bilateral hydronephrosis, hydroureter, and hydrocolpos was heterozygous for a pericentric inversion of chromosome 18, 46,XX,inv(18)(p11q21). The normal mother and her father had the same inversion. The abnormal phenotype of the girl could be due to undetectable recombination or to a position effect. She had a low level of the enzyme peptidase-A whose locus is on 18q, while her mother and grandfather had normal levels. The two other cases of familial inversions for chromosomes 18 in the literature both involve the same (p11 leads to q21) region. These three families give a tentative figure of at least 10% as the risk for a normal carrier of this pericentric inversion to have an affected offspring due to recombination.
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Two further cases (one previously published as D/D translocation) of 15/15 translocation in Prader-Willi syndrome are reported, which brings the total cases of this specific chromosomal anomaly in connection with this specific syndrome up to three or possibly four. It is suggested that Prader-Willi syndrome might be caused by loss of short arm material of chromosome 15.
A 16 years old girl with Turner syndrome was found to have a 45,X/46,X,t(XqXq)?(q27q23) constitution. The two X chromosomes are attached by their long arms with loss of chromosome material and have one active and one inactive centromere. Analysis of replication patterns with autoradiography and BrdU treatment showed that the abnormal X is always the late replicating one and that the short arm of the second X which is adjacent to the inactive centromere maintains a degree of replication autonomy from the rest of the long arm.
Anopheles atroparvus has two pairs of autosomes similar in length and morphology and two sex chromosomes with equal, heterochromatic, late replicating long arms with homologous C-, G-, and Q-bands. The short arm of the Y is shorter than that of the X and both are euchromatic. The mean number of chiasmata per cell in the male is 3.2. During mitosis there is a high grade of somatic pairing but X and Y, which form a heteropycnotic mass in the interphase nucleus, have a differential behaviour. The chronology of DNA replication was studied in spermatogonia and brain cells by autoradiography. It is hypothesized that the present sex chromosomes of A. atroparvus evolved by accumulation of sex determining factors and gene deterioration resulting in heterochromatinization of the long arms, followed by structural rearrangements.--The homology of the two sex chromosomes requires limited dosage compensation which is achieved either as in Drosophila by modifier genes or by accumulation on the short arm of the X, only of female determining factors which do not require dosage compensation.
A woman from the Trento district of Northern Italy was found to have albumin of a variant type only. Her parents were first cousins and she had two daughters who were both alloalbuminemic. This is probably the first case of a homozygote for a slow albumin variant and it indicates that individuals with only electrophoretically unusual albumin are physiologically normal.
The long arms of the X and Y chromosomes of the mosquito Anopheles atroparvus (2n equals 6) are equal in length, synchronous in their late DNA replication and have homologous G AND Q bands. This indicates that differentiation of the two sex chromosomes was the consequence of a single deletion of an autosome to give the Y chromosome, not followed by the acquisition of differential heterochromatic blocks.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.