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Genes, Populations, and the Environment Biology Basics 3 BB3.1 Genes and the Environment Interact More than genomes affects traits and diseases Environmental factors include • Prenatal environment • What we eat, breathe • Where we live Multifactorial traits, affected by both genetics and environment BB3.2 Genetics Affect Perception of and Response to Environment People’s senses react differently Some people cannot taste a chemical called phenylthiocarbamide (PTC) Genetic basis: • • aa: AA or Aa: Nontasters Tasters Population Distribution of Tasting Impact of Genetics on Food Choices Two groups of tasters: tasters and supertasters ~25% of people are nontasters, ~50% are tasters, and ~25% are supertasters May correlate with the aa, Aa, and AA genotypes Supertasters can have > 10X taste buds as nontasters and have intense tastes Supertasters High-sugar foods too sweet, coffee is bitter, and hot peppers and spices more intense, unpleasant Less likely to include certain foods and beverages in diet BB3.3 Variations in Responses to Drugs and Medicines Range of reactions to drugs and medications, may be genetically influenced Example: Rate metabolized affects dosage Some capsules delay the release of the drug Others drugs produced in variety of dosages BB3.4 Relationship between Cancer and Environment Indirect and direct evidence that environment plays important role in cancer Some environmental factors implicated in cancer • • • • Natural radiation Occupational exposure to chemicals Virus infections Personal choices: exposure to UV, smoking, and diet Viral Infections: ~15% of Cancers Viral infection alone is not enough to cause cancer, other factors involved BB3.5 Genetics and Cancer Therapy > 70% breast cancer cases: estrogen sensitive Tamoxifen treats estrogen-sensitive cancer In body, inactive form converted to endoxifen Conversion of tamoxifen to endoxifen controlled by CYP2D6 Conversion of Tamoxifen to Endoxifen CYP2D6 Gene Several alleles, four phenotypes One phenotype group metabolizes tamoxifen poorly, higher risk of recurrence Genetics important in designing or specifying drug therapy BB3.6 Behavior, Genes, and Environment 5-HTT gene controls nerve impulses in the brain Variation may cause changes in stress-response behavior Two alleles: one long and one short Study of individuals ages 21–26 with ≥ 4 stress events, increased risk of depression for those with two copies of short allele BB3.7 Environmental Factors, Genes, and Immune System Autoimmune diseases: third most common form of disease in U.S. • 15–80 diseases, affect 5–8% of population • Include: diabetes, multiple sclerosis, and rheumatoid arthritis • > 75% of affected are women Distribution of Autoimmune Diseases Autoimmune Diseases Body’s immune system produces antibodies that attack specific cells and tissues Almost all tissues and organs can be affected ID environmental agents that might cause disorder Both genetic and environmental factors involved in triggering disease Autoimmune Diseases and Infections BB3.8 Environment and Distribution and Frequency of a Genetic Disorder Populations and environment play a part in genetics Geneticists often look to environment for factors that may be responsible In some cases, relationship between a gene and the environment is clearly established In others cases, link is elusive and still unknown