You registered with EDGI UK, completed our questionnaire, and sent back your saliva kit. You might wonder, “What happens to my saliva sample?” 

The answer: DNA extraction, genotyping and genomic analysis. 

Before we start, here’s what you should know:

DNA (deoxyribonucleic acid) holds the instructions an organism needs to grow, develop, and function (Bates, 2024). It can be extracted from saliva, though saliva also contains bacteria and food particles (cue the ‘ew’ factor) that may affect DNA quality. Careful DNA extraction ensures accurate analysis.

DNA Extraction from Saliva Samples

Research Assistants Anastasia and Maria, working in the King’s Genomics lab, took the time to give us a breakdown of the DNA extraction process. 

After receiving your saliva sample, enzymes break down the cells in the saliva to release DNA. It's then warmed in an incubator before a machine automatically pulls DNA from the sample (this is known as DNA extraction). 

After extraction, DNA quality and concentration are checked with a NanoDrop. This small device uses light to analyse a tiny drop (1-1.2 microliters) of DNA and identify any impurities.

High-quality DNA extraction starts with you! Brushing your teeth, not eating for 30 minutes before, and filling the tube to the 2ml line helps our scientists get the best results.

Lab staff use Personal Protective Equipment (PPE), DNA/RNA sprays, and filter-tip pipettes to prevent contamination. Fortunately, EDGI UK samples are low-risk, so stricter protocols are unnecessary.

During DNA extraction, process details are securely stored in a lab-only database. This ensures data is available for future genomic analysis.

Genotyping: How your DNA Sample is Processed

Genotyping is a lab process examining a person’s DNA to see if certain genetic differences exist. The main difference researchers look for is single nucleotide polymorphisms (SNPs).

SNPs (pronounced as snips) are tiny DNA differences, like a typo in a book. If most people have an "A", but you have a "T", that's a SNP. If you’re interested, you can learn more about DNA structure. 

SNPs are the most common type of genetic variation - over 600 million SNPs have been found in the world’s human population (Bethesda, 2024). In research, if a group with a specific genomic variation is more affected by a disease, SNPs in the gene may indicate or lead to a higher risk of this disease. For example, studies have found variations in the NR3C1 gene strongly linked with Binge Eating Disorder (Donato et al., 2022). Visit this page to learn more about how genes contribute to disease. 

Genotyping usually starts with a polymerase chain reaction (PCR), a process which quickly produces millions of copies of a specific part of DNA.

We’ll skip the details, but here’s a nice diagram showing the PCR process!

A microarray, a tiny chip the size of a fingernail clipping (1.6834 cm2), is then used to detect SNPs in DNA. 

It contains thousands to millions of DNA spots with probes for target SNPs. PCR-amplified DNA, labelled with fluorescent dyes, is added. If the target SNP is present, it binds to the probe. After washing, a laser scans for fluorescence - if there is a fluorescent glow, the SNP is present.

Genomic Analysis & Interpreting Your DNA Sample

Our data analysis team carries out genomic analysis. We interviewed post-doctoral researchers Jared and Rujia to understand the process of performing genomic analysis. 

The data team first runs a Quality Control pipeline, checking sex mismatch, SNP missing rate, minor allele frequency (MAF), and ancestry.

The result can then be used to run GWAS and generate polygenic risk scores. Genome-wide association studies (GWAS) compare genetic differences between those with and without a trait or disease to find links. A polygenic risk score estimates the genetic risk for a trait or disease by combining multiple SNP effects. 

Often (literally 90% of the time), software is used to prepare files with information about the participants' physical characteristics for GWAS. The analysis of the files is pattern-finding mathematics at a much grander scale. A 2019 GWAS on Anorexia Nervosa, conducted by the Eating Disorders Working Group of the Psychiatric Genomics Consortium (PGC-ED), found eight specific DNA areas significantly linked to the disorder (Watson et al., 2019). GWAS results are typically visualised using a Manhattan plot.

(Yes, it’s actually called the Manhattan plot, and yes, it’s because it looks like the Manhattan skyline)

The x-axis shows SNPs, and the y-axis shows statistical significance. Each point is a SNP - the higher it is, the more significant. SNPs above the red-dotted line are considered statistically significant.

A key challenge in genetic research is having enough samples (at least 10,000) for reliable results. That’s our EDGI UK recruitment goal! 

To answer your questions about privacy, do not fret! The lab and data teams only see anonymised barcodes or encrypted IDs without personal information. Strict controls ensure only approved researchers access the data for health studies.

That was a lot to take in, but we hope it gave you a glimpse behind the scenes! If you haven’t joined EDGI UK yet, learn more and sign up on our website!