Genetics (the study of genes) is becoming increasingly important in ME/CFS research, especially considering the ongoing work of the DecodeME study and release of their pre-print results. Therefore, to help understand genetics research, we have provided simple explanations of key terms.
What is DNA?
Most cells in the human body contain DNA – molecules that act as instruction manuals for the body’s development and function.
DNA is mostly found in the nucleus of cells in tightly wound up structures called chromosomes, but it should be noted that mitochondria also have DNA. Humans have 23 pairs of chromosomes in almost every cell (chromosomes are passed on from both parents, with each person getting half their chromosomes from their mother and half from their father). Each chromosome contains hundreds to thousands of genes.
What are genes?
A gene is a segment of DNA that contains instructions usually for making a protein. Proteins are molecules essential for the body’s functions, from building tissues to fighting infections.
Genes can also contain instructions to make RNA – a molecule that can help make protein or work indirectly to control cell functions.
Gene expression is the process by which a gene’s instructions are used to make a protein or RNA.
Genes can also help control how cells work by turning other genes on or off.
A locus (plural = loci) is the specific location of a gene or DNA sequence on a chromosome. If the DNA of a chromosome is like a street, a locus is like an address – each gene has it’s own address i.e. locus.
An allele is a different version of the same gene.
How are genes linked to disease?
Disease may arise when genetic changes or gene variants (versions) produce faulty proteins, incorrectly regulate other genes, or disturb cell pathways (chains of interactions within cells). Nevertheless, it is often not a straightforward fact that a gene (or genes) causes disease, because disease usually occurs in combination with other factors e.g. environmental factors. ME/CFS is broadly considered to be a multifactorial disease, whereby multiple factors/mechanisms could be contributing to the manifestation of symptoms.
What is a genome?
A genome is the complete set of DNA within a cell, like a library containing all the instructions (genes) needed to keep the body functioning.
What is a genome-wide association study (GWAS)?
A genome wide association study (GWAS) is a research approach, typically including thousands of participants, that involves scanning genomes to find genetic variations linked to a disease or characteristic. DecodeME is a GWAS and the world’s largest genetic study of ME/CFS.
An advantage of a GWAS is that it looks at the entire genome without needing to know in advance which genes to investigate, thus it is possible to discover new or unexpected links to a disease. Hence, a GWAS helps reduce the risk of confirmation bias, which is a greater risk in smaller scale genetic research that does not involve the entire genome. Nevertheless, there is still value to other genetic study types e.g. for testing specific genes and hypotheses.
