Module 29 Lecture Slides

• LG 29.1 Phenotypes are the product of an organism’s genes and its environment. • LG 29.2 Genes and the environment affect human health and disease. • Most phenotypes are influenced by a large number of genes. • The environment can have a major impact on phenotypes. • The ability of a single genotype to produce different phenotypes in different environments is known as phenotypic plasticity. • Some animals, like grey treefrog tadpoles, can change phenotypes in response to predators. • Phenotypic plasticity is pervasive in nature. • Some animals change phenotype in response to changes in the environment • The fur color of snowshoe hares changes as the seasons–and the outside temperature–change. • In most alligators and lizards, temperature can determine the sex of offspring. • Embryos incubated at lower temperatures develop into females, and those incubated at higher temperatures develop into males. • Phenotypic plasticity is common in plants. • Plants can respond rapidly to changes in the environment, such as in jewelweed, which grows taller in response to shade from neighboring plants. • The effects of genes and the environment can interact in a variety of ways, with some genotypes exhibiting no response to environmental change while others exhibit a large response to environmental change. • Many environmentally-induced changes in phenotypes are the result of evolution. • Pythons increase the size of their digestive organs when the organs are needed, and shrink them when not eating. • Many phenotypically plastic traits have evolved due to phenotypic tradeoffs. • Genes and environments affect human health and disease. • Most diseases are determined by a large number of genes along with a substantial contribution from the environments to which a person is exposed. • A useful approach to examine the role of genetics versus the environment on human diseases is examining twins. • Monozygotic twins develop from one fertilized egg that has split in two, and dizygotic twins develop from two eggs fertilized by two different sperm. • Any differences in phenotypes between identical twins cannot be due to differences in their genetics; it can only be due to differences in their environments. • Any differences in phenotypes between nonidentical twins can be due to differences in the genotypes and differences in their environments.