Table 1.

Tools for assessment of radiation injury using cytogenetic biomarkers

Cytogenetic biomarkers	Particulars	References
Conventional cytogenetic biomarkers
Total number of aberrations	The radiation damage is quantified by scoring different types of chromosomal aberrations, and is considered to be one of the accurate technique among cytogenetic tools used as biological dosimeter. This technique is used to estimate the dose–response curves and is also popular in radiation biology for radioprotective studies.	82–89,160
Dicentrics and ring chromosomes	For assessment of radiation exposure, biological dosimetry utilizing dicentric chromosomes analysis in human lymphocytes is a well-known method practiced since long ago, along with physical dosimetry for radiation dose assessment in potentially overexposed people as well as for suspected exposures to estimate risk of health effects.	11,90–101
Micronuclei assay/cytokinesis-block micronucleus assay	Micronuclei, small satellite structures, are the chromosomal fragments lacking centromeres. The frequency of micronuclei is variously used as cytogenetic biomarker. The cytokinesis-block micronucleus assay is simple in terms of scoring criteria and is a reliable and sensitive cytogenetic biomarker.	102–117
Sister chromatid exchanges	Many authors have documented that cells exposed to radiation had significant increase in sister chromatid exchanges.	87,88, 118,119
Translocations	Irradiation causes various types of DNA damage that lead to stable chromosomal aberration. Translocation chromosomal aberration is stable and can be used as biological dosimetry for dose assessment.	120–127
Premature chromosome condensation	The premature chromosome condensations assay is being used for biological dosimetry following radiation exposures. The main advantage of the premature chromosome condensations assay is that there is no need for cells to divide for evaluation of cytogenetic damage.	128–140
Molecular cytogenetic biomarkers
FISH/chromosome painting/mBAND analysis	A relatively newly developed technique, FISH has revealed unique endpoints related to radiation quality. It has now become possible to detect inter-chromosomal and intra-chromosomal exchanges as well as distribution of the breakpoints of aberrations with the help of mBAND technique.	121,122, 141,142
DNA-PK	Double-strand break repair pathways are responsible for maintaining genomic integrity, genetic instability, and neoplastic transformation. It has been speculated that DNA-PK plays an essential role in DNA double-strand break repair and maintaining genomic integrity.	143–147
hTERT (telomerase reverse transcriptase) and genomic instability	The hTERT-immortalized cells have been found to be useful for determining the effects of radiation.	148–151, 159
Cytokinesis-block micronucleus cytome assay	Development of microarray formats analysis of the chromosomal damage of human peripheral lymphocytes is done with the modern technology of integration of techniques. The cytokinesis-block micronucleus cytome assay is being utilized as radiation biological dosimetry specifically developed to assess various forms of chromosomal damage.	10,152–155
The single cell gel electrophoresis assay/comet assay	The single cell gel electrophoresis or comet assay, developed for the evaluation of DNA single-strand breaks utilizes DNA migration as a measure of the DNA damage, however, the DNA double-strand breaks can be measured by neutral comet assay.	13,15,156, 157

Abbreviations: FISH, fluorescence in situ hybridization; mBAND, high resolution multicolor chromosome banding.