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