Available online at www.scholarsresearchlibrary.com Scholars Research Library Der Pharmacia Lettre, 2014, 6 (4):234-236 (http://scholarsresearchlibrary.com/archive.html) ISSN 0975-5071 USA CODEN: DPLEB4 234 Scholar Research Library Two extremely rare cases of homozygosity of INV (9) with down syndrome Mohit Kumar 1,2 , Atul Thatai 2 and Shilpa S. Chapadgaonkar 1* 1 Department of Biotechnology, Manav Rachna International University, Surajkund Road, Faridabad, India 2 Dr. Lal Pathlabs, India _____________________________________________________________________________________________ ABSTRACT We report here two cases describing extremely rare condition of homozygosity of pericentric inversion of chromosome 9 with trisomy of chromosome 21. One of the cases also carried a Robertsonian translocation involving chromosome 14 and 21. The other case carried homozygosity of pericentric inversion of chromosome 9 with trisomy of chromosome 21. These two cases may provide a valuable evidence to establish the association between pericentric inversion of chromosome 9 and Down syndrome which has been debated in the medical community. Key words: Homozygosity, INV (9), Chromosome 9, Pericentric inversion, Down syndrome, Trisomy 21, Non- disjunction _____________________________________________________________________________________________ INTRODUCTION The most common form of inversion found in human chromosomes is a pericentric inversion of chromosome 9 (inv 9), that occurs in 1%-1.65% of the general population (1). In some of the previous reports, pericentric inversion 9 has been associated with primary infertility, secondary infertility, birth defects, abnormal pregnancies like intrauterine growth retardation (2, 3, 4, 5, 6, 7, 8). In our previous study we have established the association of pericentric inversion of chromosome 9 with infertility (9). Homozygosity for pericentric inversion in chromosome 9 is an extremely rare phenomenon with only seven reported cases out of which five were presented with infertility. It has been hypothesized that inversion 9 may be responsible for production of abnormal gametes leading to formation of unbalanced offspring in 1-10% of cases. It has been conjectured that presence of inv (9) leads to formation of a loop during meiosis I. Although recombination is somewhat suppressed within inversion loops, when it occurs it can lead to production of unbalanced gametes (10). Pericentric inversion 9 has also been implicated as a possible predisposing factor for non-disjunction and inter-chromosomal effect (11, 12). We are studying the association of pericentric inversion of chromosome 9 with various abnormalities in the Indian subcontinent. These two extremely rare cases of homozygosity of chromosome 9 with Down syndrome which have been discussed in the present paper have proven to be invaluable as evidence. MATERIALS AND METHODS The karyotyping investigations were carried out on the cultures of the peripheral blood lymphocytes by using standard cytogenetics techniques. Short-term cultures of peripheral blood or were established and they were arrested in the metaphase stage. The metaphase spreads were analyzed by the standard GTG-banding technique.