Heredity & The Environment

Unit 2-3 NotesMr. Hefti – Pulaski Biology

BackgroundGene expression often influenced by an organism’s surroundings

“Epigenetics”

InteractionCertain environmental factors “alter” how genes are read

Examples:TemperaturepHSunlightAir quality

Temperature

Siamese cat: fur on extremities grows in darker

Arctic fox: white coat in winterHimalayan rabbit: cold temperatures cause fur to darken

Reptiles: sex determination

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

Sunlight

Triggers chlorophyll production

Absence of sunlight – leaves turn yellow

In humans, sunlight triggers the production of melanin

Air quality

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

In conclusion…Gene expression depends upon:The genetic code inherited

Environmental influences

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

environment.

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

environment.

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

environment.

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

environment.