Consanguine marriages reduce genetic diversity, pose challenge in forensic DNA analysis: Study

The study titled “Consanguine Marriage leads to Hierarchical Imbalance of ABO and STR Frequency and affects the Genetic Diversity” has been published in the journal, Current Forensic Science on January 25

A recent study conducted by a scientist from the Central Forensic Science Laboratory, Pune, highlighted that consanguine marriages lead to hierarchical imbalance of ABO blood group and Short Tandem Repeat (STR) frequency and affect the genetic diversity among people. The study also underscored the challenges in forensic DNA analysis due to reduced genetic diversity.

A pic during wedding rituals. (REPRESENTATIVE PIC)

The study titled “Consanguine Marriage leads to Hierarchical Imbalance of ABO and STR Frequency and affects the Genetic Diversity” has been published in the journal, Current Forensic Science on January 25. Consanguineous marriage is defined as a union between two individuals who are related as second cousins or closer, with an inbreeding coefficient (F) equal to or greater than 0.0156, according to genetic law. Consanguineous marriages have for long been a controversial subject, with significant attention focused on their adverse health outcomes. Such marriages are remarkably prevalent, with an estimated 10% of the global population having consanguineous parentage despite the considerable risk of genetic diseases among the offspring. Apart from genetic disorders, consanguineous marriages significantly contribute to the prevalence of depression.

Inbreeding has substantial biological implications for the genetic diversity of a population. In forensic DNA analysis, STRs are commonly used markers for generating genetic profiles that facilitate individual identification. STR loci, characterised by repetitive DNA sequences, exhibit variability among individuals, enhancing their utility in human identification. However, in populations with high incidence of inbreeding, the genetic diversity of these loci may diminish, posing potential challenges for forensic analysis.

Highlighting these challenges, Suneel Prajapati, the lead researcher of the study and scientist, department of biology and DNA division, Central Forensic Science Laboratory, Pune, said, “The primary challenge in forensic DNA analysis when working with inbred populations is the diminished discriminatory power of STR markers. A typical forensic DNA profile relies on comparing multiple STR loci to generate a unique identifier for an individual. In an inbred population, where individuals may possess fewer unique alleles, the likelihood of two unrelated individuals sharing identical STR profiles increases. This phenomenon reduces the effectiveness of DNA profiling in distinguishing between individuals and may complicate criminal investigations or identification processes. In cases involving close familial relationships, such as paternity testing or kinship analysis, inbreeding can complicate interpretations and consequently increase the risk of misidentification.”

The research paper highlighted the need for further research with large sample size to explore the additional genetic markers, and advanced statistical methods which can help mitigate the impact of inbreeding on forensic analysis.

About this, Prajapati said, “In such cases, the population-specific DNA database may be one of the most effective ways to mitigate the impact of inbreeding on forensic DNA analysis. By including a diverse range of samples from populations with varying levels of inbreeding, forensic laboratories can better account for allele frequencies that are specific to that group. This approach would enhance the accuracy of DNA profiling and reduce the risk of false positives or misidentifications. Apart from that, the use of additional genetic markers beyond STRs such as single nucleotide polymorphisms (SNPs) or mitochondrial DNA may also help overcome the limitations posed by inbreeding. SNPs in particular offer a higher level of resolution and can provide more robust genetic differentiation even in populations with low STR diversity.”

“Similarly, mitochondrial DNA which is maternally inherited and highly variable, can be a valuable tool in kinship analysis, especially when STR markers fail to provide sufficient differentiation. The development of more advanced statistical models that account for population structure and inbreeding could also improve the accuracy of forensic DNA analysis. These models could incorporate knowledge of allele frequency distributions and inbreeding coefficients to provide more reliable estimates of identity and relatedness in inbred populations,” Prajapati said.