Evolutionary genetics · BEGINNER LESSON
Deleterious
Deleterious means reducing reproductive fitness in an evolutionary sense. In genetics, a deleterious variant is one that lowers the chance that its carriers leave offspring, even if that variant does not by itself prove disease causation.
What it is
In these sources, deleterious is used in an evolutionary sense: it describes something that reduces the reproductive fitness of carriers, so natural selection is expected to remove it over time. Fitness here means reproductive success, not health in a general sense. A deleterious variant can also be called damaging to biology, but those are not identical ideas.
[1] Guidelines for investigating causality of sequence variants in human disease - Nature [3] www.ncbi.nlm.nih.gov › pmc › articlesAn Upper Limit on the Functional Fraction of the Human Genome
How scientists use the word
For DNA sequence variants, researchers often ask whether a change is likely to be deleterious by looking at evidence such as sequence conservation, comparative genomics, computational predictions, and experimental assays. Conservation means that a DNA site or protein region has stayed similar across species, which can suggest that changes there are selected against. These methods help prioritize candidates, but they do not by themselves show that the variant causes a particular disease.
[1] Guidelines for investigating causality of sequence variants in human disease - Nature
Mechanisms behind deleterious effects
A deleterious effect can arise because a change alters gene function, protein function, or biological regulation. The source on aging also uses the word more broadly for cumulative harmful changes that build up with time, including molecular damage and imperfect control of biological processes. In that context, deleterious effects are described as cumulative rather than simply late acting.
[1] Guidelines for investigating causality of sequence variants in human disease - Nature [2] Aging: progressive decline in fitness due to the rising ...
Limitations and evidence levels
The same variant may be labeled potentially deleterious in many people, so that label must be interpreted in context. Strong evidence that a variant is deleterious is not enough to say it is causal for a disease trait, because causality also requires evidence that the affected DNA region has a role in the disease process. Prediction methods are limited by statistical and biological factors, and even multiple algorithms should not be treated as independent proof.
[1] Guidelines for investigating causality of sequence variants in human disease - Nature [3] www.ncbi.nlm.nih.gov › pmc › articlesAn Upper Limit on the Functional Fraction of the Human Genome
SEE THE IDEA
How deleterious evidence is interpreted
A sequence change that may affect function or fitness
Computational methods and conservation patterns suggest possible deleteriousness
The change may alter gene or protein function, or lower fitness
Requires extra evidence that the DNA region participates in the disease process
Evidence can suggest that a variant is deleterious, but that is a separate step from proving it causes disease.
A deleterious signal is a clue, not a final conclusion.
TRY IT YOURSELF
Test your understanding
Choose an answer, then check the explanation.
PUT IT TOGETHER
Match each concept to its meaning
Drag a label onto its description, or select a label and then select a description. This also works with a keyboard.
4 pairs to match
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.