Why is phenotype caused by an autosomal gene?

Phenotype is influenced by autosomal genes because these genes are located on non-sex chromosomes (autosomes) and can determine traits regardless of an individual's sex. Each individual inherits two copies of each autosomal gene, one from each parent, and the combination of alleles can result in dominant or recessive expressions that manifest as specific traits. Additionally, the interactions between multiple genes and environmental factors can further shape the phenotype. Thus, the genetic information encoded in autosomal genes plays a crucial role in the observable characteristics of an organism.