## Historical DNA profiling

As already mentioned, in some cases nuclear DNA can be degraded and it is challenging to use it for polymorphism analysis. One way to solve this problem is to use mitochondrial DNA for analysis. Mitochondrial DNA analysis played an important role in identifying the remains of the Romanov dynasty. The Romanovs were a Russian imperial dynasty whose members, headed by Tsar Nicholas II. were murdered by the Bolsheviks in Yekaterinburg in 1918. Their bodies were thrown into a mass grave that was discovered in the late 1970s. However, the remains of two bodies, Tsarevich Alexei and one of his sisters, probably Anastasia, were not found among the remains. This created a space for speculators who claimed to be the so-called tsarinas. It wasn't until several decades later that another grave was discovered nearby, where additional skeletal remains were found that suggested they might be members of the family. Based on mitochondrial DNA analysis, it was confirmed that they are descendants of the Romanov dynasty. The DNA of Prince Philip, Duke of Edinburgh (husband of Queen Elizabeth II, British Royal family), who was a relative of the Romanov family on his mother's lineage, was used for the analysis (Figure 15.5).

Polymorphisms have been described on the Y chromosome, the association of which has been linked with the geographical origin of a person. Based on the presence of a certain haplotype (grouping of polymorphism markers) on the Y chromosome, we can identify whether a given man is African or Central American, for example. In the investigation of a crime, when the DNA profile of some trace at the crime scene is not matched in the first phase with the DNA profiles in the database, any approximation of the possible appearance of the person is of great benefit to the investigation process. The trend today is to sequence the entire genome (the entire genetic information of an organism) using second-generation sequencing methods, so-called forensic genomics. However, by analysing several SNP polymorphisms, even without additional information, it is possible to estimate some phenotypic features of a person, with the most accurate results achieved when determining pigmentation - the colour of eyes, hair, and skin. In addition to DNA analysis, RNA analysis is also used in some cases. Although the cells of a given individual contain DNA with the same sequence, they differ in what RNA molecules are present and in differing amounts. Thus, we can use RNA analysis to identify the type of tissue and sometimes also to determine the time when the trace was left at the crime scene. The disadvantage of RNA molecules is that they are less stable than DNA molecules and degrade faster.

The DNA molecule undergoes several modifications, the most famous of which is methylation (adding a methyl group) to cytosine. Such modification on certain known areas of DNA can be related to age and lifestyle (see Chapter 7 - From Epigenetics to human diseases) and consequently advances in epigenetic analysis have suggested that DNA methylation markers provide more information to forensic analysis. The ability to gain detail on the age of the unknown sample and their lifestyle, such as smoking or drinking habits, can better guide police investigations when the suspect is not known.