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

Healthy lungCancerous lung

Lung & Mouth Cancer

3. Skin cancer/sun exposure/ folic acid/vitamin D Some people are genetically more susceptible to skin cancer- light-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 regions- they’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 insulin- dependent 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 protein- rich foods (milk, eggs, meat, nuts, other high- protein foods, etc.) *Doctors test for this at birth, so parents know right away if their kid has it.

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