Phenotype

Phenotype

In genetics, a phenotype is what we can see and observe in a living thing. This includes its shape, size, color, and behavior. Phenotypes cover everything from the look of an organism to how it grows and acts, like a peacock's display.

An organism's phenotype comes from two places: its genes and the world around it. Genes are like instructions inside the organism. The environment can change how these genes appear, leading to different traits. For example, Labrador Retriever coloring can be yellow, black, or brown, depending on both genes and conditions.

The idea of separating what is inside an organism (its genes) from what we see (its phenotype) was suggested by Wilhelm Johannsen in 1911. This helps us understand the difference between what is passed down through generations and what we can observe in living things.

Definition

The term phenotype describes what we can see or measure in a living thing. This includes its shape, how it grows, and its actions. For example, human blood groups are part of a person’s phenotype.

The idea of a phenotype comes from how genes work with the environment. What we see in an organism isn’t just from its genes, but also from the world around it. This mix shapes a creature’s looks and behaviors.

Phenotypic variation

Phenotypic variation is very important for evolution by natural selection. Not all changes in what an organism looks like or how it acts come from differences in their genes. Living things can change based on their environment. This means that the whole organism, not just its genes, works with the world around it to shape its traits.

Genes and the environment work together in a more complex way than just adding them up. Sometimes, an organism's looks can change a lot depending on where it lives. For example, a plant called Hieracium umbellatum grows differently on rocky cliffs compared to sandy dunes along the coast of Sweden. Even with the same genes, the plant changes its shape and leaves based on its surroundings.

Small random changes can also happen in how an organism develops. In Drosophila flies, the number of tiny parts in their eyes can differ between the two eyes of the same fly.

What an organism shows can also affect others around it. For example, a beaver builds dams, changing its environment. This is part of what scientists call the "extended phenotype."

Genes and phenotypes

Phenotypes come from how genes and the environment work together. For example, an albino look can happen when a gene linked to melanin changes. Even then, things like UV radiation can change how much melanin is made.

How much certain genes are active can change what traits an organism shows. If a gene that makes an enzyme is very active, the organism might show one trait; if it’s not very active, it might show another. Many things, like what an organism eats or stresses it faces, can change how genes act and affect its traits.

Phenome and phenomics

Not to be confused with Phoneme or Phonology.

A phenotype is everything we can see in a living thing, like its shape or how it behaves. The word phenome is sometimes used to describe all of these traits together. Studying this group is called phenomics. This helps scientists learn how genes influence these traits and can explain things like health or how well a living thing can survive.

Phenomics is also useful in farming. It can help find genes that make plants strong against dry or hot weather. In the future, phenomics might help doctors choose the best medicine for each person based on their own traits.

Large-scale phenotyping and genetic screens

See also: Genetic screen and Essential gene

Scientists use special tests to study how changes in genes affect an organism's traits. These tests help us learn what genes do. Many of these studies use tiny living things like bacteria, such as E. coli, because it's easier to change their genes.

Recently, scientists have also used these tests with animals, like mice, to study behaviors and other traits that are not fully understood. For example, they looked at how changes in genes affect learning, memory, daily rhythms, vision, and how animals handle stress.

These experiments involve mice that have changes in their DNA. The mice are then watched closely to see any changes in their behavior. These changes help scientists find new genes and understand how they work.

These studies have shown that changes in a specific gene can affect vision and even cause problems in the eyes of mice. Interestingly, the same change in a similar gene can cause vision problems in people, showing how studying animals can help us understand and possibly treat human health issues.

Evolutionary origin of phenotype

The RNA world is an idea about how life might have started on Earth. It says that tiny molecules called RNA existed before cells did. These RNA molecules could make copies of themselves.

The shape of the first RNA molecule that could help make more RNA would have been the first phenotype. The order of building blocks in that RNA molecule would have been the original genotype.