Genes vs. Environment
(Nature vs. Nurture)
Is everything determined by genetics?
• Your characteristics (phenotype) are often
a combination of your genotype (genetics)
and your environment.
• Both play an interactive role in determining
your health.
• Examples…
1. Sickle Cell Anemia
SCA is a serious (sometimes deadly) genetic
disease, but having SCA or being a carrier for
SCA is an advantage against malaria (a
communicable disease).
*Recall that a single base change in the gene
(DNA sequence) that codes for hemoglobin
causes this. Hemoglobin will clump together
inside red blood cells, giving them a sickle
shape, which is more likely to clot.
Sickle Cell Anemia
• Sickle Cell is more
common among African
Americans.
• Prognosis: patient can
live normal life if treated
• Sickle Cell is most
common in parts of
Africa, South and Central
America. Why?
– Higher incidence of malaria
due to greater number of
mosquitos carrying malaria
parasite
– Malaria parasite cannot live
inside sickle cells.
Malaria
• Caused by a parasite passed into the
blood by mosquitoes
• Symptoms:
– Flu-like symptoms
– Elevated temp., mild jaundice, enlarged
spleen
– Severe form of disease: organ distress and
failure, which can lead to death (It’s an
example of pleiotropy- where one gene
affects more than one trait.)
2. Lung & Mouth Cancer
There are mutant genes that make you more
likely to get certain cancers, but…
Lung/mouth cancer is most likely caused by
prolonged exposure to tobacco products.
These products damage DNA to cause
uncontrolled cell growth.
Lung & Mouth Cancer
Lung & Mouth Cancer
Healthy lung
Cancerous lung
Lung & Mouth Cancer
Lung & Mouth Cancer
3. Skin cancer/sun exposure/
folic acid/vitamin D
Some people are genetically more
susceptible to skin cancerlight-skinned.
Environmentally, increased sun
exposure increases the risk of
skin cancer.
*UV radiation from tanning beds
also increases the risk! New
FDA regulations may be
introduced soon for tanning
teens! (WHO found skin
cancer 75% more likely in
people who use tanning beds
in teens and 20s!)
Skin Cancer & Sun Exposure
Consuming folic acid (dark green leafy vegetables,
dried beans and peas, vitamins) reduces your
sensitivity to sun.
Sun exposure causes the skin to produce Vitamin
D. Vitamin D can prevent or treat many types of
cancer, including skin cancer. So, 15 min. of
mild sun exposure a few times each week may
be good for you!
Sun Exposure & Vitamin D
Darker skinned people have
an advantage in
equatorial regionsthey’re more resistant to
UV rays. But…
Dark skinned people who
live in cloudier regions
north of the equator need
to make sure they also
get enough Vitamin D to
make up for the lack of it
due to less sun exposure
or they will get Rickets!
One way to supplement it is
by buying Vitamin D milk!
4. Diabetes/Diet/Exercise
Diabetes Types 1 and 2
are both genetic
disorders.
Type 1 is called
juvenvile or insulindependent diabetes.
The lack of insulin
production has very
little to do with
environment.
Diabetes
Type 2 usually occurs after
age 40 and its onset is
usually brought on by
obesity. It can be
controlled by proper diet
and exercise.
Uncontrolled diabetes can
result in:
Blindness, heart disease,
circulation problems,
slowness to heal, and
amputation of limbs.
Diabetes
• Symptoms of type 2
include frequent
urination, thirst,
hunger, and weight
loss.
• Type 2 is
PREVENTABLE! Eat
healthy, exercise, and
maintain a healthy
weight.
Atherosclerosis (heart disease)
5. PKU and diet
PKU is a recessive genetic
disorder that can cause
mental retardation.
However, symptoms of
PKU can be controlled or
eliminated by giving the
baby a diet low in proteinrich foods (milk, eggs,
meat, nuts, other highprotein foods, etc.)
*Doctors test for this at birth,
so parents know right
away if their kid has it.
PKU
patients
must avoid
these
PKU
patients
may
have
these