Learn about genetics and DNA
Genes are the physical and functional inheritance units responsible for carrying the information that produces our traits. All physical characteristics we have received from generation to generation are passed down through our genes.
Genes are made up of sequences of DNA. They contain information for making specific proteins that lead to the expression of a particular physical characteristic or trait, such as hair colour or eye colour, or a specific function in a cell.
DNA sequencing is a process of determining the exact sequence of nucleotides, or bases, in a DNA molecule. The sequence of the bases (often referred to as A, T, C, and G) encodes the biological information that cells use to develop and operate. Knowing the sequence of DNA is key to understanding many properties of the genes, for instance, changes in genes that associate with any diseases.
There are now several different methods available for DNA sequencing, each with its own characteristics, and the development of additional methods represents an active area of genomics research. Next-Generation Sequencing (NGS) is currently the most widely used technique.
A gene variant is a change in the DNA sequence. It can be inherited or non-inherited. Inherited variants are inherited from parents’ reproductive cells and are present throughout a person’s life in virtually every cell in the body. Non-inherited variants occur during a person’s life and are present only in certain cells. Sometimes a child is born with de-novo variants that are not present in either of the parents.
Variants are responsible for genetic variation (such as different eye colours or blood types), which makes us unique. While most variants are harmless and do not impact a person’s health, a small percentage of them can directly cause genetic disorders or increase or decrease the predisposition to developing those disorders. The latter are called pathogenic variants.
In Eiira genetic profiles, the information on germline variants that increase the predisposition to develop cancers is used in the overall hereditary risk analysis.
Types of genetic tests
Molecular genetic tests are medical tests used to examine a person’s DNA and reveal variations in its specific parts. Those variations, termed variants or mutations, are sometimes associated with genetic disorders. Thus genetic tests can be used to diagnose a genetic disorder or to determine the risk of a person developing or passing a genetic condition down to their children.
Depending on which part of DNA or amount of DNA is profiled, molecular genetic tests can be categorised into:
- whole genome sequencing,
- whole exome sequencing, and
- targeted genotyping.
Whole genome sequencing (WGS)
WGS is the most comprehensive tool: it obtains information about the entire genome and reveals variations in any part of the genome. It is important to have information on the entire genome since variants that can lead to a genetic disorder can happen in different regions of the genome.
Although WGS is the most powerful in locating any pathogenic variants, it produces large amounts of data. In addition, it requires more sophisticated analysis, resulting in a significantly increased cost and time.
At Eiira, we offer hereditary genetic risk/predisposition profiles. Therefore we only look at germline genetics that is inherited from parents’ reproduction cells at the time of conception. The unique advantage of taking a WGS test at Eiira is that with a single test, you can enjoy lifetime updates of continuous discoveries from science.
Whole exome sequencing (WES)
WES only looks at the human exome. The exome is a collection of all exons in the genome. The exome makes up approximately 1% of the human genome but contains the majority (85%) of the disease-related variants. Whole exome sequencing is an efficient method of identifying disease-causing variants.
Compared to targeted genotyping, WES is superior as it is not limited by the number of genes (as far as it’s within the exome) and the number of diseases. However, the drawback is that if a pathogenic variant is outside the exon region, it will not be identified.
One advantage of taking a WES test at Eiira is that, with a single test, within the scope of exome and its association with hereditary risks, you can enjoy lifetime updates of continuous discoveries from science.
In targeted genotyping, often called gene panel testing, one or a subset of genomic regions (typically less than 0.5% of the genome) are isolated and analysed. There are different ways to perform genotyping, for example, by microarrays or sequencing.
This type of test is typically faster and more cost-effective and is often used when a person has symptoms, and their healthcare provider has reasons to suspect specific variants in one (or more) gene. Moreover, it is commonly used for direct-to-consumer tests to profile selected variants of specific genomic regions (but not all the possible variants in those regions).
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