Genotype-Environment Interaction and Phenotypic Plasticity

Lesson Transcript
Instructor: Kristin Klucevsek

Kristin has taught college Biology courses and has her doctorate in Biology.

It's not just what's in your genes. In this lesson, we'll begin to explore how some phenotypes are influenced by the interaction between a genotype and the environment. Further, some organisms rely on phenotypic plasticity to change in response to the environmental changes.

Genotype-Environment Interaction

You may have heard that your genes govern who you become. You may have even blamed or thanked your genes for a few things. Your height, your personality, your dimples - these are all a reflection of your genetic makeup. That's true, to a point, but it's not the whole story. After all, a set of identical twins aren't necessarily identical. Let's take for example a set of identical twins, who have identical DNA, and one of the twins enjoys sunbathing and tanning beds and the other does not. The twin who takes a liking to harmful UV rays has this orangey glow, some extra wrinkles, and a higher risk of skin cancer. The other identical twin does not. Even with the same genetics, these two individuals are individuals at the end of the day. They like different things. They will look a little different. This is due to the fact that the environment, in addition to genetics, also plays a major role in many phenotypes.

Any phenotype that is affected by more than one factor is known as multifactorial. Multifactorial, describes a trait affected by two or more factors, either environmental or genetic. A multifactorial trait could be polygenic, meaning that two or more genes influence the trait. However, it doesn't have to be. The environment can play a role in a multifactorial trait just like multiple genes can play a role in a multifactorial trait.

Here, the environment can mean a lot of things. It doesn't just literally mean the Earth that surrounds us. The environment that influences a phenotype or trait can mean things like climate and location, but it can also mean the food we eat, the drugs we take, or toxins that are around us. The environment, as it applies to multifactorial traits, is really any non-genetic contribution. The Gene-Environment Interaction describes how the genotype and the environmental conditions surrounding an individual can influence a phenotype. This can also be called the Gene-by-Environment interaction.

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Phenotypic Plasticity

So how much does the environment influence a phenotype and how much of it is actually due to genotype? The answer isn't so simple. Not all traits are multifactorial and not all traits are influenced by the environment. But, you've likely thought about this before. Yes, your genetics do play a role in your metabolism, but it also matters if you exercise and what kind of dinners you typically eat.

The main point here is that one genotype can actually have this range of phenotypes because the environment contributes to the phenotype, making the trait multifactorial. This point has a specific name. Phenotypic Plasticity is the change in a phenotype as the result of environmental conditions.

Phenotypic plasticity exists in lots of organisms, but it is a common and easy thing to observe in plants, so they are typically the best example. After all, plants are stuck in the ground, in one place, and they have little control over their environment. Unlike us, they really can't choose what to eat and they can't get up and walk away if they don't like their environmental conditions. If you don't like the freezing cold weather in northern Maine, you can just jump on a plane and head to Cancun (well, at least theoretically). But plants don't have it that easy. Therefore, the environment really is going to play a large, obvious, and scientifically observable role in many plant phenotypes.

Additionally, phenotypic plasticity means that the phenotype of a genotype changes due to the environment. That's easiest to study if the genotype is exactly the same. It's hard, and somewhat impossible, to get a bunch of identical humans, and I'm not sure you wouldn't want to do that anyways. It's not as hard to obtain a set of almost genetically identical plants. That makes it easier to study how the environment can influence a phenotype when a genotype remains constant.

Here's a simple example of how phenotypic plasticity might work in a field full of genetically identical flowers. Now, these pretty flowers grow best in the sunshine; however, some are growing under the shade of trees while others are growing in the middle of the field. Understandably, the ones growing in the sunshine are taller while the ones under shade are shorter. In fact, there is a wide range of height in these flowers if you survey the whole field. If you want to plot the heights of these flowers, you'd find a continuous variation in height. How would you know if this was due to phenotypic plasticity, or if this was just an example of polygenic inheritance - a type of inheritance that produces a similar-looking bell curve?

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