OCR A2 Biology: The Lac Operon

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The Lac Operon

Key Words

Operon: A length of DNA, which is made up structural genes and control sites. The structural genes code for proteins, such as enzymes. The control sites are the operator and a promoter reigion.

Operater and Promoter: are both genes as they are lengths of DNA , but don't code for polypeptides.

Repressor protien: Binds to the operator region, and RNA polymerase binds to the promoter region  to transcribe the structural genes.

The process takes place inside bacteria.

Enzyme Induction: 

The bacteria E.coli can synthesise about 3000 differant polpetides. However, there is great variation in the numbers of differant polypeptides within the cell. Induced enzymes just mean that the enzymes are syntheised at varying rates, according to the cells circumstances. E.coli normally repires glucose but it can also use lactose as an respiratory substrate.

The Operon:

The structural genes: Z codes for the enzyme b-galactosidase, and Y codes for the enzyme lactose permerase. (Has the base pairs for transcribe of mRNA)

The operator region…

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