How many alleles are typically present for a gene in an organism?

For most diploid organisms, which include humans and many plants and animals, there are typically two alleles present for each gene—one inherited from each parent. This characteristic stems from the diploid nature of these organisms, meaning they have two sets of chromosomes. Each chromosome pair carries one allele from each parent, resulting in the standard pair of alleles for each gene.

Even though there are exceptions, such as organisms that may exhibit more complex inheritance patterns, the typical and most straightforward scenario involves two alleles per gene. This two-allele system is foundational in understanding concepts like dominance, recessiveness, and the basics of Mendelian inheritance.