Changing an individual’s future behavior even before they’re born

This 2015 Harvard fruit fly research was a companion of the Is what’s true for a population what’s true for an individual? study.

The researchers began with the question:

“If we could rear genetically identical individuals from a variety of genetic backgrounds and rear them in the same environment, how much phenotypic variation between individuals of the same genotype would we see?”

They answered with:

“We show that different genotypes vary dramatically in their propensity for variability, that phenotypic variability itself, as a trait, can be heritable, and that loci affecting variability can be mapped.”

The specific problem that probably prompted this study was that the methodology of genome-wide association studies (GWAS) usually:

“Focuses on the average effect of alternative alleles averaged in a population.”

What this methodology often missed was:

“When phenotypic variation results from alleles that modify phenotypic variance rather than the mean, this link between genotype and phenotype will not be detected.”

The researchers altered the environment during a critical period of fruit flies’ development in order to induce epigenetic changes in the fruit fly pupae brains:

“Disruption of Ten-a [the synaptic target recognition gene Tenascin accessory] expression in midpupa affects behavioral variance [the standard statistical dispersion parameter].

In all cases, disrupting Ten-a increased the variability [the median of the absolute deviation from each observation’s median] in turning bias with no effect on the mean.”

I fully expect researchers to demonstrate that this finding has general applicability for humans, especially during womb-life. Research such as:

are steps in this direction just for one factor in the human fetal environment – stress. The effects of stressing a human fetus should be at least as significant as the effects produced on the study’s subjects with increased temperature during pupation. “Behavioral idiosyncrasy reveals genetic control of phenotypic variability”


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