Final answer:
Proteins are vital for cell function and influence organismal phenotypes through gene expression. Alleles, which are gene variations, contribute to traits like butterfly wing pigmentation, and an organism's genotype, composed of different allele combinations, determines which proteins are made.
Step-by-step explanation:
Proteins and Genotypes Influence Phenotypes
Proteins are essential for various cellular functions and, as such, are central to determining the phenotypes of organisms. The genotype, which is the genetic makeup of an organism, provides the instructions for making proteins. Different alleles, or variations of a gene, can lead to different proteins being produced, ultimately resulting in diverse traits, such as wing pigmentation in butterflies.
Alleles are inherited during sexual reproduction, where each parent contributes one allele for each gene. The combination of these alleles (homozygous or heterozygous) makes up an individual's genotype. On the cellular level, even though the genotype is constant, different cells may express different genes at different times, leading to a wide range of phenotypes. This is why various cell types within the same organism may look and function differently.
Mendelian genetics provides the basic principles for understanding how alleles are passed down and expressed in progeny. This includes the concepts of dominant and recessive alleles and independent assortment during meiosis, all of which are pivotal in determining an individual's traits based on their genotype.