Link to the lesson

Determining paternity

Around 30% of men in the US who are ordered to undergo genetic testing for paternity have no common genes with the child whose father they are suspected to be. Based on this data, over one million of Americans are estimated to raise a child not of their own without knowing it. This, along with the decreasing cost of the procedure, paternity tests are becoming increasingly common, not only in the US.

R1I95GYAiYVPL

Zdjęcie przedstawia pobieranie materiału z jamy ustnej do badań genetycznych. Laborantka pobiera próbkę śliny z wnętrza policzków pacjentki. Próbka pobierana jest za pomocą długiego patyczka zakończonego wacikiem.

The test requires taking a sample of genetic material of the child and of the suspected father. The process is usually painless; the sample is saliva with exfoliated epidermis cells, taken as a swab from the inside of the cheek. Some analytical laboratories draw blood for testing.

Currently, thanks to the Human Genome Project for the most part, several million DNA markersgenetic markerDNA markers are known: genetic sequences that are short, unique, and very variable within a human population. The presence of such unique sequences in two persons proves they are related.

With the genetic material of the alleged father and child, their genetic profiles are created and compared. If only one or two markers are identical in both, paternity is ruled out. If all the markers of the man and of the child are the same, a statistical analysis of their frequency in the given population must be carried out, which factors into the paternity probability assessment. The biological father of the child could be a relative of the tested man, or even someone unrelated to him who has a similar set of genes, although this is a very rare occurrence.

It is possible to identify the father even before the child is born. This type of test involves amniocentesis: sampling the amniotic fluid that surrounds the fetus. The fluid contains exfoliated fetal cells which can be used to isolate DNA for paternity tests. However, due to its invasiveness, amniocentesis is not a routine procedure. DNA tests have a credibility rate of 99.9995%.

Biological microtraces at the crime scene

DNA tests are a common method of identifying suspects provided they leave their genetic material at the crime scene; just saliva in chewing gum or traces on a glass or a cigarette end is enough. Forensic investigators have to collect and secure a sample so as not to contaminate it with other DNA (such as their own).

Biological materials used for DNA testing in the judiciary include:

• hair,

• traces of tissue from underneath the victim’s nails (collected at the time of the abuser),

• blood,

• sweat and mucus,

• saliva,

• semen.

It is only possible to identify a person based on biological material if their data has already been entered into DNA databases, which have been built by law enforcement authorities in many countries for many years. The FBI database contains around 7 million DNA profiles, while the database of the Central Forensic Laboratory of the Police in Warsaw, around 15,000 profiles.

DNA profilesDNA profileDNA profiles are created based on patterns with selected characteristic DNA sequences combined with markers (fluorescent labels). The sample to be identified is applied to the pattern. If both the pattern and the sample contain the same genetic material fragments, they complement each other, and the marker emits light. The result is observed under a fluorescence microscope and recorded as a graph.

Identifying missing people

DNA tests are standard procedure when an unidentified person or a dead body is found, especially if fingerprints cannot be taken or there is no record of the given person’s fingerprints in available databases. From among missing persons, those of the same gender and age are selected, and biological material, e.g. from a comb or a tissue used by this person, is acquired from their family. By examining the DNA from the unidentified person and DNA provided by the missing person’s family, laboratory workers can confirm or deny the identity of this person.

Other applications of genetic tests include the identification of victims from mass graves or disasters, or victims of accidents such as mining disasters. Genetic testing are also used to identify several dozen or even several hundred years old remains. Genetic material is isolated from the bone and compared with the DNA of living relatives. This is the method of examining the degree of kinship of people buried in family graves.

Summary

• Genetic tests for paternity have a 99.9995% reliability rate.

• Genetic testing is useful for determining paternity and for identifying crime suspects, missing persons, and dead bodies.

Rf096XihQJvA4

Grafika przedstawiająca tablicę szkolną, na której znajdują się zdania do dokończenia. Finish selected sentences. 1 It was easy for me (uzupełnij). 2 It was difficult for me (uzupełnij). 3 Today I learned (uzupełnij). 4 I understood that (uzupełnij). 5 It surprised me (uzupełnij).

Grafika przedstawiająca tablicę szkolną, na której znajdują się zdania do dokończenia. Finish selected sentences. 1 It was easy for me (uzupełnij). 2 It was difficult for me (uzupełnij). 3 Today I learned (uzupełnij). 4 I understood that (uzupełnij). 5 It surprised me (uzupełnij).

How was this lesson? Did you like it? Finish selected sentences.

Keywords

DNA marker, establishing paternity, DNA profile

Glossary