General features: Includes variable mental retardation, speech impairment, hypoplasia and dysplasia of terminal phalanges, single palmar crease, cyanosed hands and feet and dysplastic, claw-like nails.Ĭraniofacial features: Includes high, broad forehead, mild micro-brachycephaly, flat occiput large fontanelle and open metopic suture in childhood, small eyes, deep set in their sockets, horizontal or down-slanted palpebral fissures, mild hypertelorism, large, full nose with a globular tip and downturned nares. The phenotypic features of the syndrome varies depending upon the partial or complete trisomy of the short arm of chromosome number 9. in 1970 and since then, more than 125 cases have been studied and reported in the medical literature. Individuals with trisomy 9p syndrome have well-defined phenotype with a female predilection. The nomenclature includes arm, region, band and sub-band in order as seen in the Figure 1. Karyotypes and structural alterations of chromosomes are described as short hand notations. Karyotyping is the basic tool of cytogenetic studies and most commonly involves G banding staining technique. 5 To understand the location of mutated genes in a chromosome locus, it is essential to understand the commonly used karyotyping terminologies. The basic elements of a chromosome includes a centromere, the chromosomal arms (short and long), telomeres and replication origins. 3 The accurate prediction of the human diploid chromosome number as 46 (i.e., males have 44 + XY and females have 44 + XX), was achieved by Tjio and Levan, which marked the beginning of a new era of human cytogenetics with its immense clinical applications with relation to chromosomal abnormalities. The origin of the word chromosome is from the Greek words “chromos” and “soma,” meaning color and body respectively.
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