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Biomedical subjects

M Y Yip

Publications and source records attributed to M Y Yip.

26 records · Page 2Linked to original sources
PubMed1981

Variation in pattern and frequency of acrocentric association in normal and trisomy-21 individuals.

Chromosomally normal and trisomy-21 individuals were studied for the ability of their nucleolus-organising chromosomes to form satellite associations in G-banded lymphocyte metaphases. Two types of parameter, absolute association frequency and relative association frequency, were used. There was no significant difference between females and males or between Caucasoids and Mongoloids for either type of association parameter in the controls, nor was there significant correlation between age (17-40 years) and either type of parameter in the controls. The pattern of two chromosome associations is accounted for by two related models in both normal and trisomic individuals. These models imply that there is an extensive polymorphism for associating ability and that this ability may be zero in individual chromosomes. Homologous do not associate preferentially with each other. The absolute frequency of acrocentric association is lower in trisomy 21 individuals than disomic controls, but the relative involvement of chromosome 21 (after correction for the trisomic state) is higher than in the controls.

Adolescent↗
PubMed1981

Correlations between relatives for acrocentric association frequency.

Acrocentric association was investigated in peripheral blood lymphocytes of twins (10 female monozygotic and 11 females dizygotic pairs), newborns and both parents (30 families), and spouses (51 pairs). Seventy two hour cultures were G-banded and scored for both absolute and relative acrocentric association frequency, except in the case of the spouse pairs where only the absolute frequency was measured. Both relative and absolute parameters of acrocentric association show positive correlations between relatives with the values being highest and most consistent in monozygotic twins, intermediate in parent and offspring, and most variable in dizygotic twins. Husband and wife pairs from our family collections show a positive correlation for the absolute parameter but not for relative parameters. The environmental factors responsible have not been identified. A rough estimate of broad sense heritability (0.81) has been made for the relative parameters. It probably contains a large component due to genetic dominance. Heritability of the absolute parameters is probably lower than for the relative parameters though estimation of its value is complicated by inconsistent results. A model is proposed to account for the variation in satellite association frequency which contains two elements: (i) The genotype determines the ratio of one chromosome type to another in the population of associated chromosomes (ii) All other environmental factors influence the absolute frequency of association without altering this basic ratio.

Adult↗
PubMed1979

Some enzyme polymorphisms in Malaysian mothers and their newborn.

Four red cell enzyme systems were studied in Malaysian mothers and their newborn belonging to three racial groups, the Malays, Indians and Chinese. No significant heterogeneity was observed in the distribution of phosphoglucomutase (PGM1), adenosine deaminase (ADA), 6-phosphogluconate dehydrogenase (6PGD) and acid phosphatase (AP) phenotypes between mothers and their newborn of the three groups. Pooled mother and child acid phosphatase data show a significant heterogeneity between the Malays and Chinese, and between the Malays and Indians. This is comparable to previous studies conducted. For the placental phosphoglucomutase (PGM3) system, a significant heterogeneity was observed between the Chinese and Malays only. No significant heterogeneity was detected in the distribution of PGM1, ADA and 6PGD phenotypes among Malays, Chinese and Indians.

Acid Phosphatase↗
PubMedDate not supplied

A new syndrome with mental retardation, short stature and an Xq duplication.

We describe a new X-linked syndrome of marked short stature, severe intellectual handicap and an unusual facial appearance. High resolution prometaphase banding showed affected males to have an X chromosome tandem duplication; their karyotypes were designated 46,dup(X) (q13.1-q21.1)Y. In carrier females the abnormal X chromosome was late replicating. To verify the duplication, gene dosage studies were performed using an enzyme assay and DNA techniques. Prenatal diagnosis is available for carrier females using chromosome analysis of amniocytes or chorionic villi.

Child↗
PubMedDate not supplied

Reassignment of human renin gene to chromosome 1q32 in studies of a (1;4)(q42;p16) translocation.

The human renin gene (REN) has been assigned to chromosome 1q42. Linkage studies are, however, inconsistent with this localization. We therefore reexamined the question of the location of REN using a patient whose distal chromosome 1q arm was translocated to chromosome 4 [(1;4)(q42;p16)]. In situ hybridization using a 3H-labelled REN probe demonstrated hybridization signals confined to the q32 band of chromosome 1, with radioactivity in the translocated 1q42 region being similar to the low levels along all other chromosomes.

Chromosome Mapping↗