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:Nontasters AA or Aa: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