Examples and explanations of Genotype vs. Phenotype

Any living thing is a result of both its genes and its surroundings. Before we can get into the details of this, we need to understand some basic genetic terms and ideas. We will explain what gene and phenotype mean, talk about how they are related, and look at why and how we might choose to study them.

What is the difference between genotype and phenotype?

The set of alleles that a person has for a certain gene is called their genotype. A person’s phenotype is made up of all of their visible traits or characteristics. A living thing’s genotype comes from its parents, but its trait is only affected by its genotype. Phenotype can also be changed by things in the environment.

What does the word “genotype” mean?

A gene is a piece of DNA that tells the body how to make a trait. Different copies of the same gene may not have the same exact order of nucleotides, which are made up of a phosphate group, a sugar, and a base. As a result, a gene can live in more than one type of living thing. Alleles are the names for these different kinds of forms. Finding the exact spot on a chromosome where a gene is located is called a locus.

Either two copies of the same allele or one copy of two different alleles are passed down from parents to children. A person’s genotype is said to be homozygous at that site if they inherit two alleles that are the same.

They are called heterozygous for that gene, though, if they have two different alleles rather than one. The different forms of the same gene are either autosomal dominant or recessive. It is always more likely for an autosomal dominant allele to be produced than a recessive allele.

The final set of alleles that a person has for a certain gene is called their genotype.

Examples of genotypes

As an example, let’s look at eye colour.

• Eye colour is controlled by a gene.
• One gene is brown, which was passed down from the mother, and the other is blue, which was passed down from the father.
• There is one blue allele and one brown allele. The blue gene is recessive (b). The child will have dark eyes if they get two different alleles. This is called being heterozygous. The child must have both copies of the blue eye gene for them to have blue eyes.

Figure 1: An inheritance chart showing how a person can get blue or brown eyes based on the genes their parents carry. The brown eye colour allele is dominant, while the blue eye colour allele is recessive.

Here are some more examples of genotype:

• What colour hair
• How tall
• Size of shoes

What does the word “phenotype” mean?

The genotype of an organism is all of its traits that can be seen. One big difference between genotype and trait is that genotype is passed down from parents to offspring, but phenotype is not.

A genotype can change an appearance, but genotype does not mean phenotype. Besides the genome, the phenotype is affected by things like

• Changes to epigenetics
• Things in the environment and the way you live

Flamingos change colour and eat fish out of a box.
Figure 2: Flamingos are white by nature; the colours in the food they eat are what make them bright pink.

Examples of phenotypes

Food, temperature, humidity, and worry are all environmental factors that may affect the phenotype. Flamingos are a great example of how the phenotype can be changed by the surroundings. Even though they are known for being bright pink, they are actually white. The pigments in the food they eat give them the pink colour.

The colour of someone’s skin is a second example. The amount and type of melanin that we make is controlled by our genes. However, UV light in sunny places darkens the melanin that is already there and promotes more melanogenesis, which makes skin darker.

Genotype vs. phenotype: looking at

To observe the phenotypic, we just need to look at an organism’s outward traits and characteristics and draw our own conclusions about it. It’s a little trickier to look at the gene, though.

Biological tests are used to look for changes in a person’s genotype, which is called genotyping. After getting the data, it can be compared to either the sequence of a different person or a database of sequences.

Before genetics, it was only possible to get partial sequences. Now we have state-of-the-art whole genome sequencing, made possible by big steps forward in technology in the last few years.

A flowchart that shows the steps needed to sequence the whole genome

Figure 3: A flowchart showing the different steps in whole genome sequencing (WGS).

(WGS) makes it possible to get whole sets. WGS uses high-throughput sequencing methods like single-molecule real-time (SMRT) sequencing to find the raw sequence of nucleotides that make up an organism’s DNA. This is an effective and becoming more cheap method.

A lot of different methods can be used to look at an organism’s genome, not just WGS.

Type vs. phenotype: why is it important to study them?

It can be very helpful in many types of study to understand the connection between a genotype and a phenotype.

Pharmacogenomics is a very interesting field. Genetic differences can happen in CYP450 and other liver enzymes that are needed to break down drugs. So, a person’s phenotype, or how well they can break down a certain drug, may be different based on the type of enzyme-encoding gene they have. For drug makers and doctors, this information is very important for figuring out the right doses of drugs for different groups of people.

I think it’s better to use both genotyping and phenotyping methods together than just gene tests. The multiplexing method used in a comparative clinical pharmacogenomics study found more differences in drug metabolism ability than would have been expected from genotyping alone. This has important implications for personalised treatment and shows how careful you need to be when you only use genotyping.

What can we do to learn more about how genetics and phenotype are connected?

Scientists can genetically change an organism so that it doesn’t produce a certain gene by using mice as models. These animals are called “knockout mice.” The phenotype of this animal can be compared to the wild type phenotype, which is the phenotype that appears when the gene is not removed. This lets us study how some genes cause certain phenotypes.

The Mouse Genome Informatics (MGI) project has made a library with thousands of phenotypes that can be made and studied, along with the genes that need to be deleted in order to make each one.

Chart of genotype vs. phenotype: