Phenotype and other Helpful Definitions

Phentoype

This is a term in biology that means a “type” or “group” which is defined by similar observable characteristics.  If you find it uncomfortable to think in terms of “phenotypes”, you can substitute in your mind words like “profile” or “group”.

Based on how important the characteristics actually are to the defined phenotype and how accurately and reliably subjects can be gathered according to those characteristics, the purported phenotype will or will not be helpful to promote an understanding of the group.  It is possible that the characteristics which define a phenotype may belong together observationally, but do not provide clarity as to the underlying biology of what you are trying to discover.

Subtype

You will also come across the word sub-type.  This is a more specific group of a phenotype.  For instance, you could say that all dogs with pronounced snouts and long hair represent a phenotype.  A subtype of that phenotype would be dogs with medium long snouts and curly long hair.

Biomarker

A biomarker is an objective, measurable indicator of a specific biological condition. This is what all medical diagnostic tests look for…the presence of a biomarker that is known to be present when there is a particular illness or condition.  This is why we get blood tests, x-rays or other imaging tests, urinalysis etc.  If the biomarker is present, one can make the diagnosis with confidence.

Endophenotype

This is a construct in the field of psychology that steps up the reliability of a phenotype but falls short of the confidence that a biomarker would provide.  A phenotype based on a heritable trait (as one example) would elevate that phenotype into an endophenotype.

Genotype

A “genotype” provides much more assurance that the group is biologically related in some manner.  Since a gene, and its effects, are real and evidence based, subjects with similar genes can confidently be studied together to improve knowledge related to that gene.  Testing for the presence of that gene would guarantee whether a subject should or should not be considered part of that group.

Pathological

The description of when something is not in a healthy or normal state and could be considered dysfunctional or diseased.