Allele frequency facts for kids

Allele frequency helps us understand the different versions of a gene found in a group of living things. Imagine a gene as a recipe for a specific trait, like eye color. An allele is one particular version of that recipe, like the recipe for blue eyes or brown eyes.

Allele frequency tells us how often a specific allele appears in a population compared to all the other alleles for that same gene. It's usually shown as a percentage. For example, if 70% of the eye color alleles in a group are for brown eyes, then the frequency of the brown eye allele is 70%.

Understanding Allele Frequency

Allele frequency is a key idea in genetics. It helps scientists study how traits are passed down and how populations change over time. Think of it as a way to measure the genetic variety within a group.

What is an Allele?

A gene is a section of DNA that carries instructions for a specific trait. For example, there's a gene for hair color. An allele is a different version of that gene. So, for the hair color gene, there might be an allele for brown hair, an allele for blonde hair, and so on. These alleles are found at a specific spot on a chromosome, which is like a long thread of DNA. This specific spot is called a locus.

How Allele Frequency is Used

Scientists use allele frequencies to understand the genetic diversity of a population. Genetic diversity means how many different kinds of genes and alleles are present in a group. A population with high genetic diversity is often healthier and can adapt better to changes in its environment.

For instance, if a certain allele is found in almost everyone in a population, its frequency would be very high, close to 100%. If another allele is very rare, its frequency would be very low, maybe less than 1%.

Allele Frequency and Natural Selection

When an allele's frequency is higher than about 1%, it often means that natural selection is helping to keep it common. Natural selection is a process where living things that are better suited to their environment tend to survive and reproduce more. This means they pass on their helpful alleles more often.

The natural rate at which new alleles appear through mutation (a random change in DNA) is usually much lower than 1%. So, if an allele is common, it's likely because it provides some advantage, and natural selection is favoring it.

What is a Fixed Allele?

A fixed allele is an allele that is the only version of a particular gene found in an entire population. This means that every single member of that population has two identical copies of that allele for that specific gene. When an allele becomes fixed, it means all other versions of that gene have disappeared from the population.

See also

In Spanish: Frecuencia alélica para niños