Induction of b-galactosidase

Induction of β-galactosidase.

Background knowledge.

DNA is reproduced by cells for each copy of cells that are made. The cell however, doesn’t need the entire DNA; and is able to turn certain bits that aren’t needed on and off. This is useful, as the cell doesn’t use up lots of energy making things that aren’t needed. For example, the enzyme amylase, which breaks down starch, doesn’t need to be made in the big toe.

The cell does this in a number of ways, one way is by ‘super coiling’, where the unwanted DNA gets coiled up into an unreadable ball or coil. This coil can’t be unwound and so the mRNA cannot read it to make the protein.

Another way of not using unwanted DNA is by adding a repressor molecule to the DNA strand, so the RNA polymerase cannot attach to it to make the protein. When the protein is present, e.g. Lactose, one molecule of lactose attaches to the repressor molecule, taking it off the DNA. The RNA polymerase can now attach to the DNA and make the gene, in this case, for β-galactosidase. When the lactose is all broken down, the repressor molecule attaches itself back onto the DNA, which stops the protein being produced.

Aim.

We can test to see if the protein is produced, by using an ONPG solution.

If lactose is present in the E. Coli nutrient broth the E. Coli may produce β-galactosidase .The β-galactosidase breaks down the colourless solution of ONPG and turn it yellow. The deeper the yellow, the more ONPG is broken down. I aim to see if β-galactosidase is made, and if it breaks down ONPG.

Hypothesis.

I believe that the E. Coli with lactose will break down the ONPG, and the β-galactosidase will break it down as well. The others won’t change colour.

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