An individual typically has two alleles per gene.
Understanding Alleles
When we talk about genes, we often encounter the term "alleles." Alleles are simply different versions of the same gene. These variations arise from slight differences in the DNA sequence of a gene. Because humans are diploid organisms, they inherit two copies of each gene – one from each parent. As such, at any specific location of a gene, an individual can have two alleles. This information was highlighted in the provided reference: "a given gene may have multiple different alleles, though only two alleles are present at the gene's locus in any individual."
Allele Diversity in Populations
Although an individual carries only two alleles for each gene, there can be many more alleles for that gene in a population. This is because mutations over time can create new versions of genes. For example, the gene for eye color may have alleles for brown, blue, green, and hazel, but a single individual can only possess two of those at a time.
Example
Let's consider a gene that controls plant height.
- A plant could have two alleles for tallness.
- A plant could have two alleles for shortness.
- A plant could have one allele for tallness and one allele for shortness.
In each of these cases, the plant only has two alleles for that gene, even though multiple height variants can exist within the species.
Key Points
- Individual vs. Population: An individual possesses two alleles for any given gene, while a population may exhibit many different alleles for that same gene.
- Inheritance: One allele is inherited from each parent.
- Location: The two alleles exist at the same location (locus) on homologous chromosomes.
