Genomics · BEGINNER LESSON
Locus
A locus is a physical site or location within a genome, such as the position of a gene or another DNA segment of interest. Its plural form is loci.
What a locus is
In genomics, a locus is the physical site where a gene or another DNA segment of interest is found in a genome. A genome is the full DNA content of an organism, and a chromosome is one DNA-containing structure within it. The idea is like a street address: it names where something is located, not what the DNA does. The plural of locus is loci.
[1] Locus [3] www.genome.gov · NHGRI-Talking-GlossaryTalking Glossary of Genomic and Genetic Terms
How location helps genetics
Scientists use a locus to talk about where a specific gene or sequence sits on a chromosome. This matters because DNA segments that are closer together on a chromosome are more likely to be inherited together. That is why a locus can help connect a gene, a variant, or another sequence of interest to inheritance patterns.
[1] Locus [3] www.genome.gov · NHGRI-Talking-GlossaryTalking Glossary of Genomic and Genetic Terms
Mechanistic context
A locus is not itself a mechanism. In science, a mechanism is the organized interaction of parts that produces a phenomenon. The locus is part of the description of where the relevant DNA is found, while the mechanism would explain how the DNA, gene product, or other parts contribute to an outcome. Mechanistic explanations focus on relevant parts, their activities, and their organization.
[2] Mechanisms in Science - Stanford Encyclopedia of Philosophy
Limits of the idea
A locus gives a position, but by itself it does not explain function, cause, or effect. It is also not the same as a correlation pattern or a statistical score. For example, an LOD score, which means logarithm of the odds, is a statistical estimate about whether two loci are likely to be near each other on a chromosome and inherited together.
[2] Mechanisms in Science - Stanford Encyclopedia of Philosophy [3] www.genome.gov · NHGRI-Talking-GlossaryTalking Glossary of Genomic and Genetic Terms
SEE THE IDEA
From DNA location to inheritance questions
The DNA framework where positions are mapped
The physical site of a gene or DNA segment
Nearby positions can be inherited together more often
A statistical estimate about whether two loci are near each other
A locus marks a location on DNA; proximity between loci can support inheritance questions, and statistical tools can estimate that proximity.
The diagram shows that a locus is a location first, while inheritance and statistics are separate ideas built around that location.
TRY IT YOURSELF
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PUT IT TOGETHER
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Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.