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M K McCormick

Publications and source records attributed to M K McCormick.

26 records · Page 2Linked to original sources
PubMed1990

Clinical, cytogenetic, and molecular genetic characterization of two unrelated patients with different duplications of 21q.

We present 2 patients with dup(21q). Patient MP01 had mild mental retardation, facial findings characteristic of Down syndrome (DS), and a terminal duplication of chromosome 21. His karyotype was 46,XY,dup(21) (q22.1-qter). Patient MP03 had mild mental retardation, minor anomalies not characteristic of DS, and a duplication of the proximal long arm of chromosome 21, karyotype 46,XX,dup(21) (q11.2-q21.2). The patients were studied with single-copy DNA sequences from 20 loci on chromosome 21 to characterize the extent of the duplicated regions at the DNA level. DNA loci from D21S55 to COL6A1 were triplicated in patient MP01 while loci from D21S13 to D21S8 were triplicated in patient MP03. Our results support the hypothesis of a critical region of chromosome 21, which in triplicate is responsible for many of the facial changes associated with DS. Other genes outside this region may also contribute to other abnormalities observed in DS.

Adult↗
PubMed1990

Clinical, cytogenetic, and molecular evaluation of a patient with partial trisomy 21 (21q11-q22) lacking the classical Down syndrome phenotype.

The clinical, cytogenetic, and molecular studies of an individual are presented here for the purpose of further characterizing what regions of chromosome 21q are essential for expression of the typical Down syndrome phenotype. This individual had a de novo, unbalanced translocation chromosome interpreted as: 45,XX,t(18;dup[21q]). Physical examination revealed mild manifestations, but not the typical phenotype of Down syndrome. The patient was studied using 20 single copy probes known to map to the 21q region. DNA polymorphism and dosage analyses showed triplication of loci D21S13 through D21S58 involving 21q11 to 21q22.1, and possibly involving the 21q22.2 region. Her clinical presentation, which did not include the classical findings of Down syndrome, suggests that regions distal to 21q22.1, when present in triplicate dose, account for the major manifestations of the classical phenotype. However, duplication of the area between the centromere and 21q22.1 may contribute to some of the other abnormalities in Down syndrome.

Adult↗
PubMed1990

YAC cloning of DNA embedded in an agarose matrix.

Yeast artificial chromosome (YAC) cloning of DNA in agarose is an alternative method to cloning from aqueous solutions. It minimizes any shearing that may result from handling of high molecular weight DNA and can be done with nanogram to microgram amounts of material, which facilitates construction of YACs from sources of DNA other than genomic DNA isolated from cells. The average size of the YACs recovered (200-1000 kb) and efficiency of transformation of ligation products (200-1000 cfu/micrograms) are similar to those reported using aqueous protocols. This method has been used to construct chromosome specific YACs, and it should be possible to apply the technique to the construction of chromosome specific libraries using flow sorted chromosomes as source material, and the cloning of restriction fragments isolated by preparative pulsed field gel electrophoresis.

Animals↗
PubMed1989

Molecular genetic approach to the characterization of the "Down syndrome region" of chromosome 21.

The cytogenetically defined "Down syndrome region" of chromosome 21 has been characterized by DNA analysis in patients with partial trisomy 21 with or without Down syndrome features. Single-copy DNA sequences mapped on chromosome 21 were used to determine copy number by polymorphism and/or dosage analysis in the patients. Given our results, which in some patients were in disagreement with their cytogenetic descriptions, trisomy for locus D21S13 through locus D21S58 is excluded from significant contribution to many Down syndrome features. The minimal chromosome region necessary in triplicate to result in the Down syndrome phenotypes in the patients characterized includes the area from locus D21S55 to locus COL6A1. We could not analyze the region between loci D21S58 and D21S55 and between COL6A1 and 21qter at the molecular level due to a lack of DNA probes and, consequently, the contribution of these areas to a Down syndrome phenotype when present in three copies is unknown. The molecular cloning and mapping of chromosome 21 and the expansion of the patient population studied will likely result in a more precise molecular definition of the Down syndrome region.

Blotting, Southern↗
PubMed1989

Construction of human chromosome 21-specific yeast artificial chromosomes.

Chromosome 21-specific yeast artificial chromosomes (YACs) have been constructed by a method that performs all steps in agarose, allowing size selection by pulsed-field gel electrophoresis and the use of nanogram to microgram quantities of DNA. The DNA sources used were hybrid cell line WAV-17, containing chromosome 21 as the only human chromosome and flow-sorted chromosome 21. The transformation efficiency of ligation products was similar to that obtained in aqueous transformations and yielded YACs with sizes ranging from 100 kilobases (kb) to greater than 1 megabase when polyamines were included in the transformation procedure. Twenty-five YACs containing human DNA have been obtained from a mouse-human hybrid, ranging in size from 200 to greater than 1000 kb, with an average size of 410 kb. Ten of these YACs were localized to subregions of chromosome 21 by hybridization of RNA probes (corresponding to the YAC ends recovered in Escherichia coli) to a panel of somatic cell hybrid DNA. Twenty-one human YACs, ranging in size from 100 to 500 kb, with an average size of 150 kb, were obtained from approximately equal to 50 ng of flow-sorted chromosome 21 DNA. Three were localized to subregions of chromosome 21. YACs will aid the construction of a physical map of human chromosome 21 and the study of disorders associated with chromosome 21 such as Alzheimer disease and Down syndrome.

Cell Line↗
PubMed1984

A method for coping with overall productivity when making between-group category comparisons.

A straightforward method for dealing with the effect of response productivity when comparing individual scoring categories between groups was presented along with an example. It was contended that percentage comparisons based on group data can circumvent the reliability problems associated with percentage scores derived from single protocols. Other problems connected with ratio and percentage scores were discussed.

Journal Article↗
PubMed1983

Validity of the hand test for diagnosing organicity in a clinical setting.

When validated against a clinical sample, the Hand Test was able to differentiate between 50 brain-damaged and 50 functionally disturbed individuals with 69% accuracy. Significant variables were Description, Withdrawal, Pathology, Automatic Phrasing, Gross, Hiding, and Demonstration. The Hand Test seems to have some value for diagnosing organicity, but it should be used with caution and preferably as part of a test battery.

Adult↗