Transcript Document

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:
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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
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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