How nice would it be if you could get to know you?
All of you? Genetic testing can tell you what makes you you.
But more importantly, it can tell you what diseases you have increased susceptibility
for. How, well it all began with the Human Genome Project.
The Human Genome Project, which operated from 1990 to 2003, was one of the great feats of
exploration in history.
The project, led by an international team of researchers, looked at sequences and maps of
all the genes of humans.
It provided researchers with basic information about the sequences of the 3
billion chemical base pairs adenine, thymine, guanine and cytosine.
These base pairs make up human genomic DNA deoxyribonucleic acid, which is a complex
molecule that contains all the information necessary to build and maintain a human
being. The Human Genome Project revealed that there are approximately 25,000 human
genes. The completed human sequence can now identify the location of each gene.
During the project, researchers deciphered the human genome in three major ways,
determining the order or sequence of all the bases in our genomes.
Dna making maps that show the locations of genes on our chromosomes, which are
structures that carry our genetic information, which is passed on to children.
And finally, by producing what are called linkage maps, through which inherited traits,
genes that you get from your parents can be tracked over generations.
There are various ways that the Human Genome Project has allowed for genetic testing.
These include sequencing, other model organisms, development of high throughput
sequencing techniques, and examination of ethical concerns associated with each issue.
As of 2016, more than 7000 completed genome sequencing projects have been reported.
The Human Genome Project allowed for sophisticated computational and mathematical
approaches to data, which brought many fields close with biology.
These include computer science, mathematics, engineering and theoretical physics.
Together, these created a cross-disciplinary culture and made data available in databases
such as GenBank and USC and gave rise to the field of bioinformatics where computer tools
are used for processing of large biological data.
This allows scientists to simultaneously scan a person's genome for thousands of
single nucleotide polymorphisms or snips.
Snips are single nucleotide differences between different people and occur almost
once per every 1000 nucleotides, meaning that there are 4 to 5 million snips in a
person's genome.
SNPs are highly beneficial in genetic testing as they serve as biological markers
for monitoring, disease emergence and drug efficacy.
Genetic testing looks at changes in the DNA referred to as mutations.
Mutations in the DNA are also termed genetic variants.
Mutations and genetic variants are the underlying reason behind many diseases and
medical conditions.
Mutations can be categorized based on where they occur and how they occur.
For instance, cystic fibrosis occurs due to a single point mutation in a gene on
chromosome number seven.
A point mutation means that a single nucleotide changes, which changes the protein
sequence as a result.
Also, the fact that the mutation occurs on chromosome seven suggests that the genetic
disease is autosomal and not sex linked.
Sex linked disorders only occur in sex chromosomes, which are the 23rd pair of
chromosomes in every human.
Advances in Human Genome Project has allowed scientists to determine the ancestry of human
populations. However, 99.9% of DNA is similar among all human species, suggesting
that only a small portion of our DNA is used to derive information about our ancestry.
Taking a saliva sample from one person allow scientists to compare it to reference snips
in the database.
These reference snips are more common in certain populations in the world, which
allows researchers to deduce an estimate of your ancestry.
However, this method still has its limitations because multiple snips can be
found in multiple populations, making it difficult to deduce accurate results.
Similarly, SNPs can also help with tracking disease hesitance in a family because SNPs
occur in a gene or in a regulatory region near the gene.
These diseases with family inheritance include diabetes, cardiovascular diseases,
hypertension and Alzheimer's disease.
The Ethical, Legal and Social Concerns of Human Genome Project, known as ELSI are
important because the impact of genetic information can be extreme.
The positive impact of using genetic testing for disease diagnosis can have negative
psychological impacts on the individuals.
These individuals have been reported to feel fear and helpless.
There is also a problem with privacy and confidentiality of genetic information.
Who should have access to this information?
Is it right for someone else to have access to this information other than the patient?
There are several different ways for genetic testing to be done, depending on the goal.
Molecular tests look for changes in one or more genes.
These types of tests determine the order of DNA nucleotides in an individual's genetic.
A process called DNA sequencing.
The first type of molecular test is a targeted single variant test that looks for a
specific variant in one gene.
This variant is known to cause a disorder.
This type of test is often used to test family members of someone who is known to
have a particular variant to determine whether they have a familial condition.
For example, there's a specific variant in the HBB gene that causes sickle cell disease.
A second molecular test is a single gene test.
Single gene test?
Look for any genetic changes in one gene.
These tests are typically used to confirm or rule out a specific diagnosis, particularly
when there are many variants in the gene that can cause the suspected condition.
Gene Panel testing is a third type of molecular test.
This test looks for variants in more than one gene and is often used to pinpoint a
diagnosis. When a person has symptoms that may fit a wide array of conditions, or when a
suspected condition can be caused by variants in many genes.
The final type of molecular test is large scale genetic testing, which analyzes the
bulk of an individual's DNA to find genetic variations.
It is typically used when single gene or gene panel testing has not provided a diagnosis or
when the suspected condition or genetic cause is unclear.
There are two different kinds of large scale genetic tests whole exome sequencing, which
looks at all the genes in the DNA and whole genome sequencing, which looks at all of a
person's DNA, not just the genes.
These tests are ordered for people with complex medical histories and are used in
research to learn more about the genetic causes of certain conditions.
Large scale genetic tests can have findings unrelated to why the test was ordered in the
first place, such as finding genes associated with a rare heart condition when
you're looking for a genetic diagnosis to explain a child's developmental disabilities.
Apart from molecular tests, there are also chromosomal tests and gene expression tests.
Chromosome tests analyze whole chromosomes to try and identify large scale changes,
including an extra or missing chromosome.
A large piece of a chromosome that is added or missing or rearrangements of parts of the
chromosome. Finally, gene expression tests look at which genes are expressed in
different types of cells.
Over-expression or other expression of certain genes can be suggestive of particular
genetic disorders, such as many types of cancer.
Although you and I share 99.9% of our DNA, the expression patterns are what make each of
us unique.
How is genetic testing done on patients?
Step one is going to the doctor's office.
Their your doctor or genetic counselor will talk to you about the test.
They inform you why you might need it, what to expect, and what the test will tell you.
Then your doctor or nurse will get a sample from you.
Samples are usually blood samples, but sometimes they can be saliva samples from the
inside of your cheek. They can also be hair samples or fluid samples, which are usually
taken from the amniotic fluid during pregnancy.
Step two is sending the sample to the lab where your DNA is prepared to find the cause
of a disease. The lab can use different ways to look at all or part of your DNA.
The way the lab looks at your DNA will depend on the type of genetic tests your
doctor ordered. The sample is then sent to the lab, where the lab technicians look for
specific changes in the DNA.
Depending on the suspected disorder, step three is called sequencing your DNA
sequencing test.
Read your DNA and look for variants or mutations in the DNA that are specific for a
certain disease. The human genome is made up of DNA and contains all of a person's genetic
information. It's like a collection of books that entail all the details of who you are.
The lab may choose to read all your DNA or books, or choose to read a part of your DNA,
which is like reading a page from one of your books.
This is all done on a machine called a DNA Sequencer.
Step four Following sequencing, the lab will begin analyzing your DNA using the computer.
All the pages of your books are put together in the right order, meaning the specific
sequences analyzed are put together.
And then, compared to DNA in the human body or the reference genome, which was discovered
through the Human Genome Project.
Step five is to analyze the variants.
The computer lists any variants in your DNA, which would be like spelling errors in your
book. Some changes are not a big deal, like spelling the word theta two different ways,
but others are more serious, like misspelling a whole word.
These changes are usually the ones that cause diseases after the variants have been
distinguished. A team of experts analyze your results.
Doctors, scientists, genetic counselors and computer experts are all on that team.
They discuss which variants may cause the disease.
They may discuss your family history and take into account your symptoms before
confirming a diagnosis and may order more tests if needed.
Step six is when the laboratory reports the results in writing to a person's doctor or
genetic counselor or directly to the patient if requested.
Despite certain caveats, there's no doubt genetic testing is an incredible medical
procedure that can inform you a lot about who you are and what your life will look like
in the future. Genetic testing is not required for everyone, and it is important to
talk to your health care professional.
Before ordering tests on your own from private companies.