Wednesday, 4 April 2012

Nurturing Nature: Genes and Behaviour

Nurturing Nature: Genes and Behaviour

The complex relationship between genes, personality and the environment was recently explored in an article written by David Dobbs[1]. Within the article, Dobbs focuses on what it is that makes some children more likely to participate in sharing behaviour than others.  Specifically, a so called ‘vulnerability gene’ was investigated- a gene can prove either detrimental or beneficial in later life depending upon environmental factors.

In a test titled, “The Bamba Test”, a friendly woman plays games with a 3-year-old child for an hour. Following this, ‘snack time’ is scheduled and the woman collects two packets of Bambas- each supposedly containing 24 corn puffs- and gives one to a 3-year-old child and the other to herself. In her packet however, there are only three corn puffs. Whether or not the child shares their Bambas is the subject of this test and according to statistics, nearly all children will not. Of the minority that shared, it was found that most children carried the “7R” variant of gene DRD4 that influences dopamine response[1]

A variant of the MAOA gene has been
researched to increase agression
This is not the first time genes, hereditary units of information passed on to children from parents[2], have been researched to cause certain behaviour. A variant of the gene SERT, responsible for decreasing serotonin levels, is linked with depression and anxiety. Similarly, a variant of MAOA is researched to increase aggression (left image). The DRD4 protein-coder, defined as dopamine receptor D4, is commonly referred to as the ‘thrill-seeking’ gene. Encoded on the eleventh chromosome pair, the 7R variant of DRD4 has been linked with diminished dopamine response[3]. This is believed to cause sensation-seeking behaviours such as ADHD[4].

Not all children with the gene variant end up with the disorder however- so, what other factors are at play?

The answer, it seems, can be found in nurture. Gene variants known to cause behavioural issues, such as “7R”, ‘only caused problems when combined with a difficult childhood’1. Hence, the “7R” version of the DRD4 gene is considered a “vulnerability gene” as there is no guarantee certain behaviour will ensue. These genes are applicable to orchid children who ‘wilt under poor care but flourish if carefully tended’1 but less so for dandelion children, who do the same regardless of their environment. Oddly, orchid children affected by these gene variants but exposed to a better upbringing seemed to generate ‘extra resilience…and a more attuned responsiveness to [their] environment’1. Thus, vulnerability genes cannot be considered flatly detrimental.

In conclusion, the question posed by the author, Dobbs, ‘Why are some children better at sharing than others?’ goes beyond purely Nature vs. Nurture and the ability to share Bambas. Combining the ‘7R’ sharing variant of DRD4 and a difficult childhood, issues such as ADHD or thrill-seeking traits can arise in later life but there is no guarantee of such behaviour. An evolving field, there is little doubt that the notion of the ‘vulnerability gene’ will gain strength in genetics of the future.

By George Hempenstall

[1] Dobbs, D 2012, ‘Orchid Children: How bad-news genes came good’, New Scientist, Magazine Issue 2849, pp42-45 

[2] Reece, J, Meyers, N, Urry, L, Cain, M, Wasserman, S, Minorsky, P, Jackson, R & Cooke, B 2012, Campbell Biology, Pearson Education, Canberra

[3] Garcia JR, MacKillop J, Aller EL, Merriwether AM, Wilson DS & Lum JK 2010, ‘Associations between Dopamine D4 Receptor Gene Variation with Both Infidelity and Sexual Promiscuity’, Binghamton University, New York, USA p2

[4] Volkow ND, Wang GD, Newcorn J, Fowler JS, Telang F, Solanto MV, Logan J, Wong C, Ma Y, Swanson JM, Schulz K & Pradhan K  2006, ‘Brain dopamine transporter levels in treatment and drug naïve adults with ADHD’, Multiple Locations, New York, USA

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