Genetic sequencing determines the exact order of an individual’s DNA building blocks. This genetic code holds information about a person, from physical characteristics to health predispositions. Sequencing reports translate this scientific information into understandable insights, helping you interpret your results.
The Building Blocks of Sequencing Results
DNA, or deoxyribonucleic acid, serves as the instruction manual for all living organisms. Its structure is a double helix, resembling a twisted ladder. The “rungs” of this ladder are formed by specific pairings of four chemical bases: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). Adenine always pairs with Thymine, and Cytosine always pairs with Guanine.
The sequence, or order, of these A, T, C, and G bases along the DNA strands carries the genetic information. This is similar to how letters in an alphabet combine to form words and sentences, conveying meaning. In DNA, these sequences encode instructions for building and maintaining an organism.
Scientists essentially “read” these strings of A’s, T’s, C’s, and G’s. These reads are then aligned and compared to a reference genome, which is a representative example of a species’ genetic code.
Identifying Genetic Differences
While human DNA is largely similar from person to person, small differences in the sequence of A, T, C, and G bases exist. These variations, often called “variants,” contribute to the unique traits and characteristics of each individual. Scientists focus on these specific differences when analyzing sequencing data.
One common type of genetic difference is a Single Nucleotide Polymorphism, or SNP. A SNP occurs when a single base in the DNA sequence is changed to a different base. For example, at a specific position in the DNA, one person might have an ‘A’ while another person has a ‘G’. SNPs are the most frequent type of genetic variation among people, occurring on average about once every 1,000 bases in a person’s DNA.
Another type of variant is a small insertion or deletion, often referred to as an “indel.” Indels involve the addition (insertion) or removal (deletion) of a few DNA bases within a sequence. These differences can range from one to several thousand bases in length. Both SNPs and indels are key areas of focus for genetic analysis, as they can influence various biological functions.
Decoding the Meaning of Your Results
Once genetic variants are identified, the next step involves interpreting their biological meaning. Scientists and genetic counselors utilize extensive databases, published scientific literature, and computational tools to understand the significance of these variants. These resources contain information on variants that have been studied and associated with various conditions or traits.
Genetic sequencing can offer health insights by identifying variants associated with susceptibility or risk for certain health conditions. For example, some variants might indicate an increased likelihood of developing a specific disease or influence how an individual responds to certain medications. It is important to remember that these insights often indicate a predisposition or risk, not a definitive diagnosis, as many factors contribute to health.
Ancestry information is another common outcome. By comparing patterns of variants in your genome to those found in reference populations, genetic tests can reveal geographical origins and ethnic backgrounds. Specific DNA markers, like those on the Y-chromosome for paternal lines or mitochondrial DNA for maternal lines, are analyzed to trace ancestral connections. The accuracy of these ancestry estimates depends on the comprehensiveness of the reference databases.
Trait prediction, such as eye color, hair texture, or even certain metabolic responses, can also be inferred from genetic variants. While some traits are influenced by a few specific variants, many complex characteristics are shaped by the interaction of numerous genes and environmental factors. The field of genetic interpretation is continually advancing, and new associations between variants and traits are regularly discovered.
What to Look For in a Sequencing Report
Sequencing reports are designed to present complex genetic information in an accessible format. While report layouts may vary between providers, several key sections are commonly included to help you understand your results. Understanding these sections provides practical guidance for interpreting your personal genetic data.
A “Summary” or “Key Findings” section typically highlights the most significant or actionable discoveries from your sequencing data. This section often provides a high-level overview of the most relevant information without delving into excessive technical detail. It serves as a starting point for understanding the main takeaways from your report.
Many reports include a “Variant List” or “Gene List,” which is a table detailing the identified genetic variants and the genes where they are located. This list might include information such as the specific change in the DNA sequence and its classification (e.g., benign, uncertain significance, pathogenic). While the technical specifics can be overwhelming, the report should provide clear explanations of what each variant means.
The “Interpretation” or “Significance Section” explains the implications of the identified variants. This part often describes how a particular variant might influence health, traits, or ancestry, often referencing supporting research or databases. This section translates the raw genetic data into meaningful insights about your biology.
Reports also include “Limitations” or “Disclaimers.” These important caveats clarify what the results do and do not indicate. They might state that the results are not diagnostic, that interpretation is based on current scientific knowledge which can evolve, or that not all possible genetic variations were analyzed. Finally, a “Recommendations” or “Next Steps” section provides guidance on how to use the information, such as consulting a healthcare provider or genetic counselor for personalized advice.