1. Heredity & The Environment Unit 2-3 Notes Mr. Hefti – Pulaski Biology

2. Background  Gene expression often influenced by an organism’s surroundings  “Epigenetics”

3. Interaction  Certain environmental factors “alter” how genes are read  Examples:  Temperature  pH  Sunlight  Air quality

4. Temperature  Siamese cat: fur on extremities grows in darker  Arctic fox: white coat in winter  Himalayan rabbit: cold temperatures cause fur to darken  Reptiles: sex determination

5. Soil pH  Acidic: spruce trees turn blue  Neutral and basic: spruce trees stay green  Acidic: hydrangea flowers blue  Neutral and basic: hydrangea pink or white

6. Sunlight  Triggers chlorophyll production  Absence of sunlight – leaves turn yellow  In humans, sunlight triggers the production of melanin

7. Air quality  Identical twins with family history of respiratory disease raised in places with different air quality not equally likely to suffer ailments

8. In conclusion…  Gene expression depends upon:  The genetic code inherited  Environmental influences

9. Gene expression in an organism can be modified by interactions with the environment.