The Silverfish

I immensely enjoyed archiving A P Krishnaja’s material, primarily because as a Biology graduate with molecular biology research experience, sifting through her laboratory data felt like looking through a window to the past. Various laboratory methods have evolved over time to accommodate the growing needs of the researcher, but certain routines have been preserved from the past, albeit not the most convenient method of data presentation. The cut-and-paste method to present the chromosomes in a grid is one such protocol.

Born in Calicut, Kerala, in 1951, Krishnaja did her BSc. in Zoology (with chemistry and botany subsidiaries) at Malabar Christian College, Calicut. She worked as a telegraphist in Calicut for almost two years before resuming her academic journey.

She pursued an MSc. in Zoology by research at the Central Institute of Fisheries Education, Mumbai (CIFE) during which period she was the recipient of the Indian Council of Agricultural Science (ICAR) Junior Fellowship. After a stint studying drosophila mutagenicity at Punjab Agricultural University, Ludhiana,she earned a PhD from the Institute of Science in 1980. She worked at the Genetic Clinic and Pediatric Research Laboratory at KEM Hospital before joining the Bhabha Atomic Research Centre’s biomedical group, where she worked from 1982 to 2008. She was part of several landmark research projects at BARC such as a cytogenetic monitoring programme on human newborns carried out from 1983-1987 to find out the incidence of constitutional chromosome anomalies, as well as the international collaboration HUman Micro Nucleus Project. She also conducted an in vitro cytogenetic study in human lymphocytes exposed to quinacrine dihydrochloride (QDCL has been used as a crude chemosterilant in developing countries in recent years).

Krishnaja’s early research consisted of characterising commonly consumed fish species. She conducted enumeration of the chromosome numbers, along with physiological features of the members of the genus Labeo, which includes Rohu or the rui mach.

The methodology adopted to report the chromosome numbers was a routine procedure followed to identify and characterise species – preparing a karyotype. A karyotype is an array representation of chromosomes of an organism, much like a barcode. It serves to give us an overview of chromosome numbers of an organism, as well as characteristics of individual chromosomes. Giemsa staining, developed in 1902 by Gustav Giemsa, has been the go-to protocol to mark chromosomes in a cell, and works by conferring it unique banding patterns. Once made visible, chromosomes are observed under a microscope and “sorted out”, based on its size and the band features, to render a chart, known as a karyotype or an idiogram.

Krishnaja’s collection consists of karyotypes of fish, and patients from KEM hospital, where she worked in the latter years of her career. These karyotypes consist of cut-outs from photographs of metaphase chromosomes, pasted, with the chromosomes numbered and labelled. As tedious as this might sound, the manual cut-paste is still a go to method for idiograms because of its simplicity. With the advent of newer staining and digital sorting techniques, karyotyping has accommodated new developments. Instead of identification by banding patterns of metaphase chromosomes, staining techniques such as Fluorescent In-Situ Hybridization, or FISH, has enabled researchers to target and stain individual chromosomes using complementary nucleic acid strands.

This, combined with modern confocal microscopy, gives much higher precision and resolution to the identification process. The advent of image editing softwares such as Adobe Photoshop enables the researcher to digitally cut and paste the individual chromosomes to make the karyotype. Computer software, improved protocols and modern microscopes are integral to molecular biology research and communication now; but Krishnaja’s karyotypes and photographs of chromosomes give us a glimpse to the fundamental and rigorous methods scientists in the ‘70s adopted to supplement their paradigm-shifting research work.