DNA Profiling and Use in Forensic

Investigations and Paternity

Testsby J.C. Hall and Eli

Rosenthal

What are DNA profiles?

In 1985, the English geneticist Alec Jeffrey discovered that certain regions of DNA contained DNA sequences that were constantly repeated contiguously. He also discovered that the lengths of these sections differed from person to person, and developed a method to test for the differences in length. By comparing these sections, he developed a human identity test, known as the DNA profile.

Professor Sir Alec Jeffreys

How does DNA profiling work?DNA profiling compares the sections of DNA repeated, called variable numbers of tandem repeats, or VNTRs, of the samples from the crime scene, and compares them to samples taken from suspects. Because every person has an individual set of VNTRs, if the compiled set of VNTRs of the DNA at the crime scene matches with that of a suspect, then that person’s DNA was definitely at the crime scene. In the photo at left, the DNA profile taken from a bloodstain at the crime scene matches the DNA profile of the suspect third from the left.

DNA Profiling in the FieldCurrently, DNA profiling is only done in the lab, at a rate of up to three samples per hour, due to the process used to create the profile. However, some Australian forensics laboratories have developed or purchased analysing equipment that simultaneously runs analysis of different VNTRs, greatly improving the processing rate. Also, the U.S. Department of Justice is funding a number of research projects designed to create a DNA analyser on microchip, which would allow for quick, on-the-spot creation and storage of DNA profiles.

DNA Profiling as a Paternity TestBesides as a useful tool in forensic investigation, DNA profiling can be used to determine a person’s lineage. Different companies, such as Family Tree DNA, use DNA profiling to determine either paternal or maternal lineage. Maternal lineage is determined through testing for mitochondrial DNA, or mtDNA, which is passed down only through the mother. Paternal lineage is determined most often through a Y-STR test, which tests for very specific repeats (STRs) on the Y-chromosome, which is only passed down from males. A perfect match indicates a very close male ancestor.

Social ImplicationsThere are a variety of social implications that stem from the use of DNA profiling. These include relief for wrongly convicted persons who are freed, problems within a family when the father learns he is not the father of his child, and self-esteem issues for a child who learns of his true father. In addition, there are organisations such as the UK-based Liberty that believe keeping DNA profiles on file is a violation of the right to a private life.

TOK AspectsWhile DNA profiling is a very accurate form of identifying paternity, testing for blood groups is a simple manner to test for absence of relationships between two people. This can be considered as a less personal or less intrusive but less accurate form of determination. In addition, the importance of DNA profiling as a forensics tool can be assessed by discussing several recent high-profile legal cases, such as that of O.J. Simpson or of Kirk Bloodsworth.

Aim 7 - BioinformaticsBioinformatics is the process of applying statistics and computer science to molecular biology, and is intended to increase scientists’ knowledge of biological processes. The most common activities in bioinformatics are mapping, analysing, and comparing DNA and protein sequences, and creating three-dimensional renderings of the sequences. In keeping with its purpose of applying computationally-intence methods to statistics, bioinformaticists have developed online simulations that can be used for anything from automatically generating the products of RNA translation for an input set to calculating the amino acid composition and molecular weight of a given protein sequence. The human X chromosome, mapped by the HGP.

Human Genome Project: Background• Began in earliest stages in 1984 in the US

Department of Energy• HGP became official in 1990• Aimed to catalog the ~3 Billion base pairs in the

Human Genome• 1987 USDE report says:

– "The ultimate goal of this initiative is to understand the human genome" and "knowledge of the human as necessary to the continuing progress of medicine and other health sciences as knowledge of human anatomy has been for the present state of medicine."

• Gave rise to a multinational collaborative effort carried on university campuses to accomplish the huge task of sequencing the entirety of the human genome.

State of Sequencing process• Depending on which metric is used, the human

genome is either completely sequenced or not entirely sequenced

• Based solely on numbers, 92.3% of the genome has been sequenced– Certain aspects of the genome (centromeres, telomeres,

some loci, and various other regions) have yet to be sequenced, mostly because they are heterochromatic and are almost inaccessible with current methods

– New methods such as nanopore technology are making a full-genome sequence a more realistic and cost-effective goal

• What we have now is essentially a working reference genome

Outcomes: Knowledge Gained

• There are ~20,500 genes in humans – A little over 1 percent of this is made for

sequencing proteins.

• Specific proteins– Kinases, 2% of all human genes, are

enzymes that modify other proteins through phosphorylation,

– Ex: the CaM kinases which are instrumental in smooth muscle contraction (phosphorylates myosin) have the genes CaMK I, CAMK1, CAMK1D, and CAMK1G

Evolutionary Relationships

Analysis of various polymorphic loci in worldwide populations has given rise to analysis of the genetic relationships between different nationalities. They are also helping to answer the question of whether humans originated from 1 source or from multiple, a 2007 study concluded that all humans came out of Africa through an index of skull measurements and genetic databases.

Aim 8Aim 8

• We’re all different, but we’re all equal

• There are different genetic phenotypes in different cultures, but these are– Small differences– And should be celebrated, as a diverse

population means that the species will be able to respond to more environmental changes, and will be able to ensure continued biodiversity and variety in the gene pool.

Connection: TOK(things to note)

• In the international effort (which was unprecedented) to sequence the human genome, there were private and public efforts.– If the private endeavors succeeded, then the genome would have

been patented and used solely for profit – luckily it did not win and everyone has access to it.

• There are different ways in which this can be viewed from a philosophical standpoint– A complete account of what it means to be human, a reductionist

view that asserts we are products of a biological determinism that stems from the human genome

– A chemical grounding for something that allows different holistic traits to present themselves that are independent of the biological essentialist views.

• DISCUSSION OF THE NATURE OF LIFE?!?!?!?!? – This can be a good place to debate essentialism vs. existentialism,

as well as psychoanalysis and modern iterations of vitalism.