Indian Journal of Genetics and Molecular Research

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Keywords: Nijmegen Breakage Syndrome; Chromosome Instability; Recurrent Infections. 

Keywords: Karyotyping; Cytogenetics; Molecular Biology. 

 Gene expression is the conversion of DNA into messenger RNA (mRNA), which are translated into proteins that perform critical functions of the cells. Microarray is a high-throughput technique for studying global gene expression profiling.  Microarray mainly works based on the principle of hybridization. Two major types of microarray chips are cDNA arrays and Oligonucleotide arrays. The principle, methodology, types and applications of microarrays are discussed in this review.  Apart  from studying  gene expression, microarrays are also used in studying Single Nucleotide Polymorphisms (SNPs), DNA methylation, micro RNA, copy number variations, etc. in the genome. Though there is a recent boom and excitement in genomic analysis using Next Generation Sequencing (NGS) methods and studying the whole genome expression profiling using RNAseq, it is difficult to substitute the microarrays in terms of diverse applications and cost effectiveness of the latter. 

 Mental retardation (MR), defined by the World Health Organization(WHO) as an intelligence quotient (IQ) <70, is characterized by significantly limited cognitive functioning, coupled with limitations in adaptive skills. Down syndrome is the most common genetic cause of intellectual disability in the population and is due to a gene dosage effect of the presence of an additional chromosome 21(Vundinti etal., 2011) or a partial trisomy, mainly in the 21q22 region (Frias etal., 2002). The main aim of this study is to evaluate the Cytogenetic causes for the occurrence of the mental retardation. The present study was carried out with 100 MR cases and 100 age and sex matched healthy controls from North Coastal Andhra Pradesh. With prior informed consent, 5 ml of blood was collected into sterile heparinized tubes from 100MR cases and 100 healthy controls for evaluation of the chromosomal abnormalities by using Leukocyte Blood Culture and G-banding techniques. Out of 100 mentally retarded people analyzed, 76(76%) had normal karyotype and remaining 24(24%) were Down syndrome. Among them regular free trisomy constituted 18(18%) cases, Robertsonian translocations in 4(4%) cases and mosaicism was recorded in 2(2%) cases. The study confirmed the findings of earlier studies carried out in India and other countries. It emphasizes free trisomy 21 was found to the most  frequent  autosomal aberration  of  Down syndrome when compared with Robertsonian translocations and mosaics.

 The distributions of ABO blood groups & Rh (D) factor have been reported among the Bhotia (Jad) of Uttarkashi district, Uttarakhand. The frequencies of blood groups among Bhotia (Jad) were as follows B(41.6)%, O(26.3)%, A(20.5)%, AB(11.6)% . The gene frequencies were found to be p= 0.1756, q= 0.3152,      r= 0.50925 and the Rh (D) negative blood groups was recorded 3.68% among this community. Further the results were compared with the other tribal populations of North India for the incidences of ABO & Rh (D) blood groups. However, these frequencies of blood groups had shown the affinity with North India tribal populations except the Hindu of Agra & Oudh and Hindu Soldier of U.P.