What are alternative forms of the same gene called?

Alternative forms of the same gene are called alleles. These alleles can be found at the same locus (position) on homologous chromosomes and are responsible for the variation in phenotypic (observable) traits among individuals within a population.

To understand this concept further, let's consider a simple example involving the gene that determines flower color in a plant species. Suppose there is a gene that controls the color of a flower, and it exists in two forms: one allele codes for red flowers, while the other codes for white flowers.

The allele for red flowers can be represented as \( R \), and the allele for white flowers can be represented as \( r \). These two alleles, \( R \) and \( r \), are alternative forms of the same gene. The combination of these alleles, which an individual inherits from its parents, will determine the flower color of the plant.

If an individual plant inherits two copies of the red allele (\( RR \)), it will have red flowers. If it inherits two copies of the white allele (\( rr \)), it will have white flowers. If it inherits one copy of each allele (\( Rr \)), the resulting flower color will depend on the dominance relationship between the two alleles. If the red allele \( R \) is dominant over the white allele \( r \), the plant will have red flowers. If the alleles show incomplete dominance, the plant may have pink flowers, which is a blend of red and white.

In summary, alleles are different versions of the same gene that can lead to variation in the physical appearance or function of an organism's traits. The specific combination of alleles that an organism has is known as its genotype, and the resulting physical trait is its phenotype.