How Does the Genotype Determine the Phenotype?
Genes control the phenotype, the structural and functional properties of an organism. Since it is clear that phenotypes have evolved and diversified over the history of life, it stands to reason that genes controlling the phenotype have evolved as well. How do genes evolve? The ultimate cause of evolution is the accumulation of mutations in the DNA of an organism. Mutations can be caused by a number of factors, including errors made by DNA polymerase during replication of the genome, by reactive molecules in the cell, and by external factors such as x-rays. Eukaryotes utilize many mechanisms, including repair enzymes, to fix mutations when they occur, but inevitably some mutations are not corrected and are then passed on to future generations. The overwhelming majority of mutations are harmful or neutral with respect to the fitness of the organism possessing them. However, when advantageous mutations occur, natural selection tends to increase their frequency in a population.
