Environment and Phenotype

Upper SixthBiology

Aims

• To understand• The effect of the environment on the

phenotype• Specific examples• The function of the lac operon in E

coli

Phenotype

• Phenotype = Genotype + environment

• Height in humans• Fur colour in the Himalayan rabbit• Many characteristics are determined

by the information help in the genes and also the environment

The lac Operon in E coli

• E coli is a bacteria normally found in the gut• It needs enzymes to carry out the breakdown

of nutrients• Lactose permease, Β galactosidase• The expression of these genes depends on

the environment• If the bacteria is grown in glucose, it doesn’t

produce either• If grown in lactose, both genes are expressed

Some work

• SAQ 4.22 please, in your books

• Why waste the resources to make enzymes that you don’t need?

The lac operon

• What is an operon?

• A length of DNA that holds the base pairs of a structural gene (one that makes a protein) and another base sequence which determines whether or not the mRNA to make the structural genes are transcribed or not.

Lac operon Lactose present

The lac Operon in E coli- no lactose present

Lac operon Animation

• Lac operon