Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: matthewh on 07/06/2019 10:57:30
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Sera has two questions for us today:
First, in cases where a trait is influenced by multiple different genes, is it possible for the trait to be expressed when the person only has some of these gene variants?
Second, if a trait is caused both by genetics and environmental factors, is it possible for someone who doesn't have the gene variant in question to express the trait just from the environmental factors?
Let's see if someone can factor in their answers to these questions!
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Many traits are not "all or nothing"; traits like height are influence by many environmental and genetic factors, and produce a continuum of heights.
- The very fact that height forms a bell-shaped distribution (if you select individuals of a similar age) is an indication that it is produced by many factors.
- It doesn't make sense to say that someone doesn't "have" a height. If they have matured normally, they will express a height.
- And it is quite possible for someone with short parents to be taller than their parents, if they have better nutrition, less disease, etc.
A long term question in genetics has been the estimate of genetic vs environmental influence (as determined from twin studies, for example) has not be borne out by gene sequencing studies.
- There are many potential reasons
- Some say that there are many small contributions from different genes (or epigenetic markers); the frequency of these small contributions is too small to show up in DNA sequencing surveys
- Conversely, others have suggested that there are some large contributions from rare genetic variants; the frequency of these rare contributions is too small to show up in DNA sequencing surveys
- The question is still to be resolved
See: https://en.wikipedia.org/wiki/Missing_heritability_problem