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Interaction of phenotype and genotype: nature and nurture go hand-in-hand for life

31 Mar

“[…] When a sperm and an ovum combine into a zygote, they establish the genotype: all the genes that the developing person has. Creation of a person from one cell involves several complex processes to form the phenotype – the person’s appearance, behavior, and brain and body functions. Nothing is totally genetic, not even such obvious traits as height or hair color, but nothing is untouched by genes, not even behavior such as voting Republican or Democrat, working overtime or not at all, wanting or refusing a divorce (Plomin et al, 2013).

The genotype instigates body and brain formation, but the phenotype depends on many genes and on the environment, influenced from the moment of conception until the moment of death through “the organism’s encounters with its prenatal and postnatal environments” (Gilbert, 2010, p26). Most traits are polygenic (affected by many genes) and multifactorial (influenced by many factors).”
The Developing Person Through the Lifespan, 9th Ed., Berger

 

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ABT puppy from our 2016 litter (might be Rory?)

 

This passage came from the textbook for the Lifespan Psychology course I’m taking at the local community college. It got me thinking about the relationship between nature and nurture: gene expression is affected by the environment and the dog’s response to their environment is affected by their genes. You can’t have one without the other and you can’t change one without changing the other.

This is was a reminder for me to think globally in terms of both behavior and physical development on a lifetime scale. As a breeder I choose the genes to some extent and I also have a lot of influence over phenotype (behavioral and physical development) during the first 8-9 weeks of my puppies’ lives. Puppy owners have even more control over phenotype since they have the puppy from 8 weeks until death and as a result can influence gene expression over the lifetime. Interesting thought, isn’t it?

Epigenetics (changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself) is a fascinating topic and I suspect it’s going to have a large influence on both dog breeding and dog training in the future. There is evidence that a learned response may alter gene expression and that those altered genes may in turn be inherited by offspring who will exhibit a similar response. Another study showed that something as simple as a diet change in the pregnant mother could alter gene expression in offspring to eliminate the deleterious effects of a gene. You may not be able to change the gene itself but you can change its expression – which is just as good.

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Tig, from ABT’s 2016 litter

 

What does this mean to me? There is a great deal more plasticity in both the brain and in our genetics than we have traditionally thought. As a breeder this encourages the application of genetic preservation principles. Over the decades there’s been a trend toward breeding very few and very specific individuals but as Dr. Carol Beuchat points out this leads to inevitable inbreeding and loss of genetic diversity. Some breeds, terriers in particular, are in danger of going extinct due to miniscule breeding populations with very little genetic diversity. Would our breeds benefit from broadening the gene pool? How can we avoid extinction and improve the genetic diversity of our breeding population? These questions will need to be addressed at some point in the near future and I don’t think the answers will be popular or easy.

It also leads me to reconsider the idea that “you’re stuck with what you got” when it comes to the genetics of a puppy. The power of epigenetics means that phenotype has the potential to change as the effects of the environment alter gene expression (i.e. training, care, chronic stress). This has limited applied use since we don’t know which genes will be altered but it can be a powerful boost for folks working with difficult dogs. Rehabilitation is often primarily about behavior (phenotype), but it could have an effect on gene expression which in turn will effect behavior. It also highlights the importance of thinking holistically about the care and keeping of your dog for their mental and physiological health.

In the end breeders, owners, and trainers are in the same fluid relationship with gene expression as the organism is with nature-nurture. We can influence behavior and gene expression through breeding and training knowing the consequences can be multi-generational genetically and global phenotypically. There is a sense of freedom and exploration here that pushes the boundaries of what we think we know.

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