PART 3 QUESTION 6

Question 6 

The DNA profile showed evidence for a father and son. In addition there was DNA profiling pattern that matched one living twin (Tanya Rosilawati). With this, match the evidence to these victims who were earlier filed for missing persons. Explain your rationale.

 

DNA profiling is also called DNA testing, DNA typing, or genetic fingerprinting. It is a technique  employed by forensic scientists to assist in the identification of individuals by their respective DNA profiles. DNA profiles are encrypted sets of numbers that reflect a person's DNA makeup, which can also be used as the person's identifier. "Wikipedia"

Methods used for DNA testing are:

1.    ABO blood group typing

2.    Analysis of various proteins and enzymes

3.    Human leucocytes antigen

Current technique is using polymerase chain reaction (PCR) and restriction fragment length polymorphism by electrophoresis.

The procedure for creating a DNA fingerprint:

1.       A sample of cells containing DNA from each skulls and jaw structures in the crime scene are taken. If only a small amount of DNA is available for fingerprinting, a polymerase chain reaction (PCR) may be used to create thousands of copies of a DNA segment.

Watch the video here :

http://www.britannica.com/EBchecked/media/16680/Specific-segments-of-DNA-are-amplified-in-a-laboratory-using

 

2.       The DNA extracted are then purified.

3.       The DNA is cut at specific points along the strand with restriction enzymes. This produces fragments of varying lengths that are sorted by placing them on a gel and then subjecting the gel to an electric current (electrophoresis).The shorter the fragment the more quickly it will move toward the positive pole (anode).

4.       The sorted, double-stranded DNA fragments are then subjected to a blotting technique in which they are split into single strands and transferred to a nylon sheet.

5.       The fragments undergo autoradiography in which they are exposed to DNA probes—pieces of synthetic DNA that have been made radioactive and that bind to the minisatellites.

6.       A piece of X-ray film is then exposed to the fragments, and a dark mark is produced at any point where a radioactive probe has become attached.

7.        The resultant pattern of these marks are analysed.

Watch the video here :

Each chromosome contains many sections of non-coding DNA. These do not code for a protein, but contains areas called short tandem repeats (STRs). The STRs are used in DNA profiling. In a pair of chromosome, the individual will carry one STR from his mother and one STR from his father. 

 

 

When the DNA profile of a child is compared to the profiles of the child's genetic parents, it is possible to match one line in each STR area.

In a DNA parentage test, the result obtained is known as the probability of parentage. If the alleged parent is not biologically related to the child, the probability of parentage calculated will be 0%. However, the probability of parentage is typically 99.99% if the alleged parent is biologically related to the child.

In testing the paternity of a male child, comparison of the Y chromosome can be also used. The Y chromosome inherit from his father will undergoes little or no change. Males who are biologically related in this way will have practically identical Y-STR profiles, while males who are not related will have unique Y-STR profiles. While Y-chromosome comparative analysis can determine whether males are paternally related, it cannot determine the nature of the relationship—whether they are father/son, uncle/nephew or grandfather/grandson.

By taking samples from the skulls and jaw structures, we did DNA profiling for 3 of the victims and compare each of their results. The DNA result taken from the female child’s jaw is different from the other 2 victims. Besides, we have determined that the other 2 victims in the crime scene are biologically related.

So, we came out with a second hypothesis that picture 1 and 2 are male skulls.  With the evidence provided, our forensic dentistry team matched the DNA analysis results with the list of reported missing people. According to the list, there is only one case where Herman Hartono and his son, Adi Hartono were reported missing. We did parenting testing and Y-chromosome comparison test for both of the male adult skulls to determine whether both individuals are biologically related.

 

Picture above shows one STR area taken from a DNA fingerprinting results. The DNA banding in male skull picture 1 is very similar to the DNA banding in male skull picture 2.

The probability of parenting in both male individuals is 99% and the Y-chromosome comparison testing shows identical Y-STR profiles. This concludes that they are both father and son. From this point of view, we believe that the two male skulls fragments were belong to them.

While for the child’s jaw structure, we suspected it belongs to one of the twin name, Anya who was reported missing few months ago. Tanya who is suspected to be twin sister of the deceased was called over and her DNA specimen is taken to be compared with the DNA from the young child’s jaw structure. After DNA testing, it has clearly shown that both specimens share exactly the same DNA profile. As we know, no two people have the same DNA sequence except identical twin. Our team is very confident that both of them are identical twins. So we can conclude that Anya is one of the victim in the crime scene.

Previously in part 2, we had made a hypothesis that there is one adult male, one adult female and one child 
male victims by looking at the skulls and jaw structures. Unfortunately the assumption made was incorrect. DNA 
fingerprinting state that the child’s jaw turn out to be belongs to a female and the other two 
skulls were belong to male adult. It might be due to examining pictures in different angles which make us can hardly 
identify the skulls and jaw structures among adult and children, male and female. 
DNA analysis shows a more accurate result.

Reports of missing people

                             

Results of DNA profiling from the skull and jaw structures

 

Matching of evidences to the victims 

References :

•  Encyclopædia Britannica, Inc  http://www.britannica.com/EBchecked/media/16680/Specific-segments-of-DNA-are-amplified-in-a-laboratory-using
• DNA profiling http://en.wikipedia.org/wiki/DNA_profiling 
• Y Chromosome comparison test http://www.dna-bioscience.co.uk/service_ychromosome_test.php