Part III: Murder Most Brutal! Q7

Evidences we have collected at the crime scene

Evidence 1 : human skull with large jaw bearing five teeth

Evidence 2 : jaw bearing three back teeth

Evidence 3 : jaw with some teeth still in eruption

The DNA profile showed evidence for a father and son, and DNA profiling pattern that matched one living twin (Tanya Rosilawati).

List of missing person : Herman Hartono and his son, Adi Hartono who lived a few blocks away from here. Also, Anya Suriati and Tanya Rosilawati, a pair of 9-year old twin girls, whose father filed a missing person’s report of Anya four months ago


Before we analyse the evidences, let’s talk about the DNA profiling techniques and also the extraction of DNA from then bones and teeth.

There are 2 DNA profiling techniques. The techniques are Restriction Fragment Polymorphis(RFLP) and Polymerase Chain Reaction(PCR).

• Restriction Fragment Polymorphis

Restriction fragment length polymorphism or RFLP analysis is used to identify a change in the genetic sequence that occurs at a site where a restriction enzyme cuts. It is usually used to trace inheritance patterns, identify specific mutations, and for other molecular genetic techniques.

Figure 1 : Steps for RFLP analysis

•  Polymerase chain reaction

PCR (polymerase chain reaction) analysis is usually the first step in the creation of a DNA profile today. PCR can replicate a small amount of DNA to create a larger sample for analysis. It does this using a repeating process that takes about five minutes.

Steps for PCR analysis :

1. Add a heat-stable DNA polymerase into the DNA sample to bind to the DNA and allows it to replicate.
2. Heat the DNA sample to 200 degrees F (93 degrees C) to separate the threads.
3. Let the sample to cool after heating then reheat it again. This is because reheating will double the number       of copies.
4. Repeat this process about 30 times, so that there is enough DNA

Figure 2 : How PCR works

PCR is the first step in analysing Short Tandem Repeats(STRs- very small, specific alleles in a variable number tandem repeat). Apparently, analysing STRs is more accurate than the RFLP technique because their small size makes them easier to separate. Y-STR is a variation on STR analysis and it is the only STRs found on the Y-chromosome (which only males have) is analysed.

Figure 3 : Y-STR profile

Steps for DNA extraction from ancient teeth and bones.

Figure 4

Now, we shall start analysing our evidences. We will start off with evidence 3, which is a jaw with some teeth still in eruption. Matching the DNA profile and also the list of missing person, we can believe that the victim is Anya Suriati. Firstly, Anya Suriati is 9-year old girl, not all teeth will be erupted at that age, and this point has fulfilled the evidence 3. To double confirm this, DNA extracted from the tooth attached to the jaw(evidence 3) matches with Tanya Rosilawati’s DNA, which is Anya Suriati’s twin. Identical twins have the exact same DNA because they came from the same fertilized egg as shown in Figure 6. Thus, with all these evidence, we can conclude that evidence 3 belongs to Anya Suriati.

Figure 5 : DNA profile of identical twins

 

Figure 6: Fertilisation of one ovum by one sperm resulting in identical twins as shown.

Now there are 2 unidentified evidences left, evidence 1 which is the human skull with a large jaw bearing 5 teeth and also evidence 2 which is a jaw bearing 3 back teeth. Both evidences were from 2 different individuals. According to the DNA profile, it showed evidence of a father and son. To confirm the relationship of a father and son, DNA extracted from both evidence 1 and 2 are compared. The two DNA profile pattern matches half of it or by analysing both their Y-STR(as mentioned above) will confirm their father and son relationship.

Again, by matching the DNA profile with the list of missing person, we can believe that these 2 evidences from 2 different victims were belong to Herman Hartono and his son, Adi Hartono.

We can also conclude that both these jaws are belong to victims 17 years and above because both jaws have their 3rd molar(wisdom tooth) erupted already. We cannot differentiate between the evidences if it belongs to the father or the son unless the DNA of the victim Adi Hartono’s mother is collected also. Whichever tooth(from either evidence 1 or 2) has its DNA profile pattern matches half of the DNA profile pattern of the victim Adi Hartonno’s mother will show that that particular evidence belongs to the son and the other one belongs to the father. This is because the mother and father does not share the same DNA. Refer to Figure 7.

Figure 7 : The DNA profile pattern of child and parents.