Human female germ cells has two X chromosomes and human male has one x and one Y chromosome. If the fertilization occurs via X-bearing sperm results in female offspring and fertilization by Y-bearing or X-deficient sperm results in make offspring. This ability of male gamete to determine the sex of the offspring and the presence of unique Y chromosomes in male gamete lead to the foundation of the paternal testing (Bachtrog 2013). Parental testing via Y chromosome is done with the help of the DNA fingerprinting or DNA profiling.
The parental testing is indeed helpful for a woman to scientifically pinpoint the father of a child who is refusing to take the financial responsibility of the child. On contrary, a woman may also seek to avoid sharing the custody of child with her former husband who she knows is not the actual biological father of the said child takes the help of DNA profiling in parental testing. At times, a adopted child may vouch for the information of his or her actual biological father/mother and then again the importance of DNA profiling in paternal testing comes into consideration (Buckleton et al. 2016).
The majority of the violent crimes are committed by the male and in majority of the cases; there are sexual offences where the female victims become pregnant. Therefore in order to ascertain the prime culprit, the only sample which is being left behind is the sperm. Since Y chromosome is the determinant of maleness, Y chromosome is used as the basic pillar behind the paternal testing via the process of DNA fingerprinting or DNA profiling (Toom 2012).
About Y chromosome
Unlike the X chromosome, human Y chromosome has long been ascertained to be genetically blank. However, later it was proved that Y chromosomes contains few genes than that of the x chromosome. The pseudoautosomal regions (PARs) of Y chromosome (located at two of the extreme ends) share the homology with the X-chromosome and the remaining 95% of the Y chromosome does not share homology with the X-chromosome and is known as non-recombining region of Y chromosome (NRY) or male specific region of the Y (MSY). The MSY is divided into euchromatic regions (gene rich) and heterochromatic regions (lacking genes). Within the euchromatic region, adjacent to the PAR, there lies sex determining region of Y (SRY). This euchromatin region or the gene rich region of the Y chromosome is the principal target for DNA profiling in the paternal testing (Jangravi et al 2012).
The intergenic portion of the DNA which makes up most of the gene is a mixture of unique and repetitive sequences which are arranged in tandem and are known as satellite. These satellite provides a valuable tool for genetic engineering. In case of paternity testing, Variable Number of Tandem Repeats VNTRs) is used. VNTRs are associated with the alterations in the degree of repetition of the microsatellites and this gives the basics of the DNA fingerprinting in paternal testing (Poznik et al. 2012). DNA fingerprinting technique was discovered by Alec Jeffreys et al. in the year of 1985 and first DNA fingerprinting application occurred in Bristol, UK (1987) in order to investigate a case which have link in between burglary and rape. DNA fingerprinting can be generated via simultaneous use of random probes or site specific probes. Jeffrey used multi locus probes which are repeated in tandem within the intron of myoglobin gene (Roewer 2013).
Method used by Scientists
The most common methods which are being sued by the scientist parental testing is DNA fingerprinting. In this case, the researchers use the micro-satellites or short tandem repeats (STRs) as probes.
The DNA is isolated from the gene rich region of the Y-chromosome.
The isolated DNA was then amplified in PCRs via the use of STRs as probes which are specific to the gene rich or the euchromatin region of the Y-chromosome
The amplified DNA is then subjected to restriction digestion, (a process known as Restriction fragment length polymorphism or RFLP).
The digested DNA fragments are them subjected to agarose gel electrophoresis. In this process the DNa gets separated on the basis of their charge/mass. Here the smallest DNA migrates faster under the response of the charged electric field.
This isolated DNA is then subjected to Southern blot hybridization. Here the DNA is samples are sieved out of the agarose gel using a nylon membrane and that too under the application of the charged electric field. In the running buffer certain chemicals are used which separates the double stranded DNA samples as single stranded DNA. The single stranded DNA gets cross linked under the influence of the uv light.
The radio labelled probe (microsatellite) is then allowed to bound with this single stranded amplified DNA and then an X-ray film is placed over the nylon gel in order to detect the pattern of radio activity.
The visible pattern of the radio band is what known as DNA fingerprinting. This pattern of band is then compared with the father in order to detect the similarity.
However, in recent times, the after the product of the PCR is subjected to restriction digestion and this digested DNA fragments is then subjected to sequencing. The sequencing pattern between the son and the suspected father is compared in order to detect the homology (Dolf 2013).
Relevant Social Issues
There several social issues associated with the parental DNA profiling.
There are several risk associated with the DNA profiling in parental testing like emotional, social and financial consequences. People at times may feel insulted, angry or anxious about the results. Genetic testing creates tension in the family as the result may reveal uncomfortable information about the other family members. Moreover, it may also invite in the possibility of genetic discrimination in the sectors of employment and insurance. According to the lawyers who specializes in the family law are of the opinion that the, test ostensibly offers clarity but the results creates unchartered emotional terrain.
In case of parents who have adopted a child, the demand of paternity test affects them badly. The legal parents who have given their heart and soul to raise the child may get hurt by the child’s demand to hunt their biological father. On the other hand, a man may tend to generate disgust and avoid taking financial responsibility of a child and discovering that the child whom he is nurturing is not his biological counterpart (Milunsky 2012).
Moreover, the paternity test done via DNA profiling may tend to generate false positive results. The STR (small tandem repeat) or small nuclear polymorphism (SNP) is unique in every individual and hence when random STRs are used as probe, it may lead to the generation of the false positive results (Pena 2013; Lu et al. 2012).
The DNA profiling for paternal testing is proved to be extremely helpful for the women who are fighting for the financial rights of their children with their biological fathers. In most of the caes, these women are rape victims. The person found guilt often denies to take the responsibility of his children claiming that the boy or a girl is does not bear his share of chromosome. However, with the advent of the paternal testing via DNA profiling or DNA fingerprinting, it has become easier in the judicial grounds to detect the actual biological father of the children and claim their deserved rights in the society. Moreover, the DNA profiling also found to be extremely useful to detect the convicts of the rape case (Alrc.gov.au 2017).
On the other hand, the orphan children who are leaving in an orphanage may use the process of DNA fingerprinting to detect their biological father and claim their family rights in the society. The same theory holds true for the children born as a result of the artificial reproduction or in-vitro fertilization (Ravelingien and Pennings 2013).
Other supporting views include
Men have right’s to test or claim their paternity
Children have rights to know their biological parents
Bachtrog, D., 2013. Y chromosome evolution: emerging insights into processes of Y chromosome degeneration. Nature reviews. Genetics, 14(2), p.113.
Buckleton, J.S., Bright, J.A. and Taylor, D. eds., 2016. Forensic DNA evidence interpretation. CRC press.
Toom, V., 2012. Bodies of science and law: forensic DNA profiling, biological bodies, and biopower. Journal of Law and Society, 39(1), pp.150-166.
Jangravi, Z., Alikhani, M., Arefnezhad, B., Sharifi Tabar, M., Taleahmad, S., Karamzadeh, R., Jadaliha, M., Mousavi, S.A., Ahmadi Rastegar, D., Parsamatin, P. and Vakilian, H., 2012. A fresh look at the male-specific region of the human Y chromosome. Journal of proteome research, 12(1), pp.6-22.
Poznik, G.D., Henn, B.M., Yee, M.C., Sliwerska, E., Euskirchen, G.M., Lin, A.A., Snyder, M., Quintana-Murci, L., Kidd, J.M., Underhill, P.A. and Bustamante, C.D., 2013. Sequencing Y chromosomes resolves discrepancy in time to common ancestor of males versus females. Science, 341(6145), pp.562-565.
Roewer, L., 2013. DNA fingerprinting in forensics: past, present, future. Investigative genetics, 4(1), p.22.
Dolf, G., 2013. DNA fingerprinting: approaches and applications (Vol. 58). Birkhäuser.
Milunsky, A., 2012. Genetics and the Law. Springer Science & Business Media.
Pena, S.D. ed., 2013. DNA fingerprinting: state of the science. Springer.
Lu, D., Liu, Q., Wu, W. and Zhao, H., 2012. Mutation analysis of 24 short tandem repeats in Chinese Han population. International journal of legal medicine, 126(2), pp.331-335.
Ravelingien, A. and Pennings, G., 2013. The right to know your genetic parents: From open-identity gamete donation to routine paternity testing. The American Journal of Bioethics, 13(5), pp.33-41.
Alrc.gov.au. (2017). Social consequences of parentage testing | ALRC. [online] Available at: https://www.alrc.gov.au/publications/35-parentage-testing/social-consequences-parentage-testing [Accessed 12 Sep. 2017].Lu, D., Liu, Q., Wu, W. and Zhao, H., 2012. Mutation analysis of 24 short tandem repeats in Chinese Han population. International journal of legal medicine, 126(2), pp.331-335.