Phenotypic Frequencies

As you may already know, the Genes found in an organism make up its Genotype. The genotypes organisms are inherited from their parents. Genes can help determine the physical attributes of an organism, and these visible physical attributes are known as a Phenotype. These attributes include traits such as hair color, eye color, height, and wing length. These phenotypes that makeup populations are able to be broken up into fractions. Each fraction represents a different physical feature and how common it is in the population. This is known as phenotypic frequency.

Phenotypic frequencies definition

Phenotypic frequencies are the number of organisms in a population with a certain observable trait. This does not take into account Alleles that are recessive and are not physically visible.

Phenotypic frequencies properties

Remember, phenotypes are the visible traits seen in an organism, so there are numerous examples of phenotypes. Alongside visible traits like height, eye color, and hair color, there are also behavioral phenotypes.

Behavioral phenotypes consist of cognitive, personality, and behavioral patterns. Examples of these can be self-injury, screaming, and aggression. However, there is much debate between scientists on whether or not a disorder falls into a behavioral Phenotype.

A more well-known form of behavioral phenotypes is displayed in dogs.

Phenotypic frequencies examples

Using an example of a fly's wings for our phenotype, we can clearly see how phenotypes and genotypes work together. Figure 1 below shows that flies that have ww alleles will be homozygous recessive and have clearly wrinkled wings. Any other fly will have visibly normal wings due to either having the dominant W allele.

Figure 1. Flies wing appearance and their genotypes. Source: National Human Genome Research Institute via commons.wikimedia.org

Phenotypic frequencies formula

There is a formula that can be used to assess the phenotypic frequencies of a population.

The formula is: \[\frac{\text{number of copies of allele A in population}}{\text{total number of copies of gene in population}}\]

Phenotypic frequencies formula examples

Let's say that we have an assortment of twenty roses that come in various colors. We have five red roses, eight white roses, and seven pink roses. What is the phenotypic frequency for each color of rose?

We can begin by finding the phenotypic frequency for the red roses.

• \(\frac{5 \text{ red roses}}{20 \text{ roses }}\) = \(\frac{1}{4}\)
• This shows that a quarter of this rose population is red.

Next, let's solve for the phenotypic frequencies of white roses.

• \(\frac{8 \text{ white roses}}{20 \text{ roses }}\) = \(\frac{2}{5}\)
• This shows that two-fifths of the population is white.

Finally, let's look at the phenotypic frequency of pink roses.

• \(\frac{7 \text{ pink roses}}{20 \text{ roses }}\) = \(\frac{7}{20}\)
• This shows that seven-twentieths of the rose population is pink.

Remember, your answers for each phenotypic frequency should be able to be added together to equal one. This is a good way to check your work! Also, if you ever need your phenotypic frequencies in the form of a percentage, you can just multiply them by 100.

That gives us:

• 25% red
• 40% white
• 35% pink

Let's try another example! This time we have frogs, and there is 456 total. 180 are solid green, 100 are green with spots, 150 are yellow, and 26 are yellow with spots. What are the phenotypic frequencies of each frog coloration?

Let's start by finding the frequency for the solid green frogs.

• \(\frac{180 \text{ solid green frogs}}{456 \text{ frogs }}\) = \(\frac{15}{38}\)
• The phenotypic frequency is fifteen-thirty-eighths or around 39%. This will be our largest phenotypic frequency for this example.

Next, let's find the frequency for green frogs with spots.

• \(\frac{100 \text{ green frogs with spots}}{456 \text{ roses }}\) = \(\frac{25}{114}\)
• The phenotypic frequency is around 22%.

Now, let's find the phenotypic frequency for yellow frogs that do not have spots.

• \(\frac{ \text{ yellow frogs}}{456 \text{ frogs }}\) = \(\frac{25}{76}\)
• The phenotypic frequency is around 33%.

Finally, we can solve for the number of frogs that are yellow with spots.

• \(\frac{26 \text{ yellow with spots}}{456 \text{ frogs }}\) = \(\frac{13}{228}\)
• The phenotypic frequency is around 6%.

Once we finish finding all of the phenotypic frequencies, we can add them all together to make sure they add up to 100%.

• 39% solid green frogs + 22% green frogs with spots + 33% yellow frogs + 6% yellow frogs with spots = 100%.

What is the difference between phenotypic frequencies and allele frequencies?

There are many differences between phenotypic and allele frequencies, and these mainly come from alleles and phenotypes being somewhat related, but still very different things. Phenotypes are the visible traits of an organism, while alleles are forms of a gene that determine the visible traits of an organism. Alleles will count each form of a gene, while phenotypes count only the visible qualities.

Phenotypes can also be known as traits, while alleles can also be known as genotypes. Alleles can only be found in the loci of Chromosomes.

Differences between genotypes and phenotypes

Genotypes are an organism's entire genetic code, while phenotypes are just the expressed traits from this genetic code. As mentioned previously, phenotypes can be altered by the environment, but genotypes cannot because it is inherited information from an organism's parents.

Why do we want to study phenotypic frequencies?

Scientists like to study phenotypic frequencies to see the prevalence of traits within a population over time. For example, they can see if potential Gene Mutations or Genetic Drift have occurred over time, and they can also assess the Genetic Diversity within a population. Also, they can try and predict what traits future generations will have. Recent studies have also shown that phenotypic frequencies can aid in adapting to new or fluctuating environments. Phenotypic frequencies can also aid in the agricultural industry by speeding up the harvesting of crops with similar size, ripeness, and shape phenotypes.