Normal Chromosome Karyotype Research Articles

Specific recognition and differential affinity of meiotic X-Y pairing sites in Lucilia cuprina males (Diptera: Calliphoridae)

Meiotic pairing of X and Y chromosomes in male Lucilia cuprina was studied by cytological observation of normal, rearranged and deficient sex chromosome karyotypes in spermatogenesis. Two X-Y pairing regions located distally in each arm of the X and Y chromosomes were defined. Contrasting with findings in Drosophila melanogaster, these pairing regions show specific recognition of their partners. By studying rearranged sex chromosomes short arm pairing was localised to their distal ends, closely associated with secondary constrictions containing nucleolar organisers in both sex chromosomes. Short arm pairing is very tight and not greatly disrupted by chromosome rearrangement, deficiency for the Y chromosome long arm or the presence of supernumerary X chromosomes. The pairing region of the long arms could not be precisely localised but probably also occurs at their distal ends. Pairing between the long arm sites is much weaker and is easily disrupted by chromosome rearrangement, failing completely in flies deficient for the Y chromosome short arm. No cytologically visible pairing was seen between X chromosomes and the remainder of the Y. In males with an extra X chromosome, the ends of both X chromosomes pair to form multivalents with normal and rearranged Y chromosomes provided the Y short arm is present, otherwise an independent X chromosome bivalent is formed. The mechanism of pairing in male Lucilia sex chromosomes thus seems to depend on specific loci of distinctive structure within the X and Y heterochromatin. Comparison of cytological and genetic data shows that increasing cytological pairing failure is matched by higher genetic X-Y nondisjunction but that the former occurs at much higher levels. In some karyotypes cytologically observed X-Y pairing failure is not matched by high frequencies of nondisjunction presumably because weak pairing associations are disrupted during slide preparation.

ARHINENCEPHALY WITH NORMAL KARYOTYPE ASSOCIATED WITH HYPOCALCEMIC CONVULSION

The patient was a male infant who was born at the 39th week of gestation. He had cleft lips and palate, low set ears, myogenic torticollis in the left neck, clubhand in both 5th fingers, dysplasia of the penis, and cryptorchism. Although he had convulsion due to hypocalcemia 9 days after birth, this improved 25 days after birth by the administration of a calcium agent. Five months after birth, cleft lip plastics were performed. Six months after birth, an apnea attack occurred and cyanosis was observed during examination of the optic fundi. Two days later, he died. Chromosomal analyses has revealed a normal chromosome karyotype 17 days and again 4th months after birth. Autopsy findings showed the brain to be normally separated into two cerebral hemispheres but lacking in olfactory bulbi and tracts. Also observed were an atrio‐septal cardiac defect, Meckel's diverticulum in the lower small intestine, and enlarged renal pelves. Retinal and choroid defects were seen at the sites where giant papillae were found in examination of the optic fundi.

Testicular feminization syndrome: A review and report of 6 cases

Testicular feminization is a hereditary variant of male pseudo hermaphroditism manifested in a phenotypically normal female with sparse or absent pubic and axillary hair, the absence of the uterus, and the presence of gonads that are histologically like undescended testes. These patients have a normal male chromosomal karyotype and negative sex chromatin. This disorder appears to be inherited on the basis of either a sex-linked recessive or a sex-limited autosomal dominant gene. In these patients, the testicular Miillerian inhibitor factor may be present normally, whereas the testicular Wolfan duct stimulator may be totally lacking. The failure of masculine development in utero, plus the failure to virilize at puberty, is currently believed to be due to an inherent inability of the end organ to respond to androgen. Six cases of testicular feminization are summarized.

Possible Oral-Facial-Digital Syndrome in a Surviving Male

In the May issue of Pediatrics (37:812, 1966), Dr. Jacob Wahrman and his colleagues reported a male child with the oral-facial-digital syndrome whose chromosome karyotype revealed that in actual fact he was also an example of a Klinefelter's Syndrome 47 (XXY). Since the majority of these cases have been female, the authors reviewed previous published male cases and came to the conclusion that the gene for the OFD Syndrome would be lethal in a male with a normal male chromosome karyotype.

Holoprosencephaly: A case report with no extracranial abnormalities and normal chromosome count and karyotype

A case of holoprosencephaly with no extracranial abnormalities, normal chromosome count and karyotype, and interesting laboratory findings is presented. It is suggested that when extracranial abnormalities, such as polydactyly or cardiac defects are also present, chromosomal trisomy 13–15 is found, but when only a few extracranial abnormalities are associated with holoprosencephaly, a normal chromosomal karyotype is often found. This suggestion supports the findings of other investigators. This case presented some unusual laboratory findings which are described.