The phenotype are the characteristics that we can observe in an organism, that is, its physical characteristics. In humans, examples of phenotypes are skin tone, eye color, height and weight. The phenotype is influenced by the genetics of the individual (also called genotype) but also by environmental factors and lifestyle. The relationship between genotype and phenotype has several steps of complexity. On one side, the environment and lifestyle greatly influence some characteristics. Some phenotypes are more determined by genotype such as the development of certain diseases such as Huntington, while phenotypes such as weight are strongly dependent on the environment and lifestyle. On the other hand, the effect of genotypes may not be as intuitive, as when the variants are recessive or dominant. The father of genetics Gregorio Mendel studied these characteristics in the nineteenth century and explains why some phenotypes skip generations. That is, some genetic variants (called recessive) are inherited to children without manifesting, making them carriers. This is the case of the causative variant of blue eyes and blood type O.
Some phenotypes are usually linked to the ancestry of an individual by the general population, such as having light skin tones and presenting a greater European ancestry or having curly hair with African ancestry. However, some of these phenotypes are determined by a small number of genes such as blue eyes. Therefore a Mestizo individual by chance can count on a large percentage of indigenous ancestry and blue eyes of European origin, since the few European variants of the individual fell into the particular gene that defines that phenotype. Or on the contrary, that an individual with a considerable European percentage has a darker skin tone. This may result in alleged disagreements between the percentages of the individual's ancestry and their phenotype. Another aspect to consider is that some of these characteristics, such as light skin tones, they are not as associated with ancestry as one usually thinks. For example, it has been observed that the alleles responsible for having lighter skin are not exclusive to European populations. Among some indigenous groups in America there are also variants that generate this phenotype and date thousands of years before the arrival of the Spaniards.
The phenotype depends on many factors, although there is a relationship with the genotypeSometimes inheritance patterns are not as obvious due to the random process that inheritance represents. The relationship between the appearance of the individual and their ancestors is not so direct. Not counting the many factors that play an important role in the phenotype, such as the effect of the environment and lifestyle.
Juan Esteban Rodríguez R.
Sources: Adhikari, K., Mendoza-Revilla, J., Sohail, A., Fuentes-Guajardo, M., Lampert, J., Chacón-Duque, JC,… & Jaramillo, C. (2019). A GWAS in Latin Americans highlights the convergent evolution of lighter skin pigmentation in Eurasia. Nature communications, 10 (1), 358.