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What is Gentest? The complete WIRED manual



With the spread of these clinical tests, scientists also tried to delve deeper into the DNA, whose chemical structure had not been decrypted until 1953 by James Watson, Francis Crick, and Rosalind Franklin. Over the next few decades, scientists recognized that its helical pattern of base pairs – adenine, thymine, cytosine, and guanine – acted like letters, spelling words that would break a cell into amino acids, the building blocks of proteins. You would also realize that most of the human genome – about 98 percent – does not code for proteins. In the 1970s, "junk DNA" became a popular term for these non-functional areas.

Not long after, a British geneticist named Alec Jeffreys in 1

984 came across the use of all this so-called junk DNA: Fighting Crime. In these regions of the genome, the DNA molecule tends to duplicate itself as if it were repeatedly stuttering over the same word. Scientists can record and count these stuttering known as short tandem repeats. Since the number of STRs a person has in different places is specific to them, they can be used to create a personally identifiable profile or DNA fingerprint.

] Glossary on Genetic Testing

Genotyping
Test technology, often based on chips, that produces an incomplete list of unique genetic differences.

Sequencing the Entire Genome
A Method Used Previously Identify the exact sequence of your entire genome, all 6.4 billion letters.

Sequencing throughout the exome
A method for determining the exact sequence of the protein-encoding part of your genome that comprises approximately 22,000 genes.

Circumference / Depth
A measure of how often a DNA sequence has been proofread. The 30x average overlap depth is the benchmark for a high-quality sequence.

Variant
A generic term that refers to sites in the human genome that differ from a reference genome.

Single nucleotide polymorphism (SNP)
Variant defined by a letter change

Polygenic Score (PGS)
An algorithm that adds the effects of multiple variants to the probability of a physical or behavioral trait based on your predict DNA.

Genetic Preimplantation Genetic Diagnosis (PGD)
Method for examining IVF embryos for genetic defects prior to the beginning of pregnancy.

Non-invasive prenatal testing
Method of screening a fetus for certain genetic disorders by blood testing the mother. Confirming a diagnosis requires more invasive procedures.

Carrier Screen
A test used to find out if you carry genes for disorders that you might pass on to your children.

Short Tandem Repeat (STR)
A pattern of repeating sequences in the noncoding portion of your genome used for forensic DNA testing.

CODIS
A national database of genetic profiles of criminals and crime scenes run by the US government.

In 1987, this technique was first used in a police investigation that led to the arrest and conviction of Colin Pitchfork for the rape and murder of two young women in the UK. In the same year, Tommie Lee Andrews, who raped and stabbed a woman in Florida, was the first person in the US to be convicted of DNA evidence. Since then, forensic DNA testing has left millions of criminals behind bars. In 1994, the Congress signed the DNA Identification Law, which mandated the US Federal Bureau of Investigation Authorities to maintain a national database of genetic profiles collected from criminals. By September 2019, this database known as CODIS contained DNA from nearly 14 million people convicted of crimes, as well as 3.7 million detainees and 973,000 samples collected from crime scenes.

During the '80s and' 90s, cops hurried to use DNA to catch rapists and killers, geneticists were slowly doing their own detective work. By linking medical records, family trees, disease registers, and STR positions and lengths, scientists began to accurately map features to chromosomes and finally identified the genes responsible for a number of hereditary diseases, including Huntington's disease, cystic fibrosis, and sickle cells Anemia. These diseases associated with single genes, the so-called monogenic states, are basically binary. If you have a genetic mutation, you can almost certainly develop the disease. And once the sequences for these faulty genes were revealed, it was not too difficult to test their presence. All you had to do was design a probe – a single strand of DNA bound to a signaling molecule that would trigger a fluorescent eruption or another chemical flare, if it found the appropriate sequence started such tests in various clinical settings Situations, ie on the order of a doctor to pilot. These included testing of the amniotic fluid during prenatal screening, testing the blood of potential parents (so-called carrier screening) and testing the cells of embryos prepared by in vitro fertilization. This is called pre-implantation diagnosis. These tests were expensive and targeted only at people with so-called family history of monogenic diseases. Developing tests to assess the risk of a healthy person developing more complex states, which are caused by the interaction of multiple genes – such as heart disease, diabetes, and cancer – would require a more detailed map of human DNA than the fragmented image that the Scientists had decrypted so far. Luckily that was just around the corner.

In 2000, a rough draft of the human genome sequence was made freely available online, followed three years later by a more complete, high-resolution version. This gave scientists and engineers enough information not to populate chips with one or two DNA probes, but with thousands or even hundreds of thousands. These microarrays enabled one person's genome to be scanned simultaneously for thousands of SNPs or single nucleotide polymorphisms-individual changes in the arrangement of DNA letters that make humans unique. These SNPs or variants, as they are alternatively called, can be counted to assess the susceptibility of a subject to various diseases.

And because this SNP snapshot technology, known as genotyping, could be made much cheaper than full sequencing in 2006, costing $ 1,000 compared to $ 1 million for a scan of the entire genome – it did not solve it just a new wave of research, but also a new industry: DNA testing directly to consumers.

From the mid-2000s onwards, dozens of companies conducted these investigations and began teaching people a new genetic experience that was not required in a doctor's office. They would take a sample of your DNA – a few laborious milliliters of drool sent through the mail – scan them, look into their ancestral past, and predict their genetic future. Previously, these tests could only provide a limited amount of information. And many companies went bankrupt as they waited for researchers to gain more knowledge about the relationships between particular genes and human traits. But a bagged Silicon Valley startup survived the creeping adoption curve (and spat on the US Food and Drug Administration) and became synonymous with the genomics business in retail: 23andMe makes the exchange of cheek cells against genetic insights almost smooth, 23Me has a lot of competition again. A recent study identified nearly 250 companies offering DNA tests that people can buy online. Most of them are susceptibility, descent and paternity tests. But others offer inheritance as infotainment – tests that provide matchmaking services, predicting children's talents, recommending proper diets, or even identifying wines that you genetically enjoy. Low-impact results – science is still too early to really predict the most complicated features. They may be fun, but do not take them too seriously. (And if you care about genetic privacy, do not take it at all!) Even medically-focused tests, such as 23andMe health reports, should be done with a grain of salt. For example, the breast cancer risk test formula is based on only three genetic variants of BRCA genes, which are common in Ashkenazi Jewish populations and associated with cancer. But there are thousands of other variants in these genes that can also increase your risk of breast cancer. It's just that 23andMe's DNA chip is not set up to capture it. In other words, a clean 23andMe health certificate should not be considered final. The company emphasizes that its tests are probability measurements that are not intended to be diagnostic. So, if something happens, you still need to see a doctor for a clinical confirmation.


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