GCSE Biology - Transgenic Animals

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What are the steps to produce a transgenic animal?

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An organism is transgenic if it has DNA that has been manipulated and had an insertion of a gene or genes as a result of genetic engineering. Now for GCSE, I don't know what depth of knowledge you need, but I'll try and make it simple for you to understand...

In order to manufacture insulin (for humans with Type 1 diabetes mellitus), instead of retrieving insulin from the pancreas of a slaughtered pig, E. Coli bacteria can be genetically modified to produce insulin.

First, the scientists will go to the pancreas of a human (where insulin is made) and find the mRNA that codes for insulin production. Remember that mRNA is single-stranded and is used during translation (at the ribosome) to make the protein. The scientists then use something called reverse transcriptase, which basically makes a complementary DNA strand to that mRNA molecule which is also single-stranded. This is cDNA.

Unlike DNA, cDNA is single-stranded. (This stuff may be higher-level for you, so just watch out and don't learn it unless you have to).

This cDNA (single-stranded molecule) is mixed with DNA nucleotides to make a 'proper' DNA strand that is double-stranded. Once the 'proper' DNA strand coding for insulin has been made, it is inserted into the plasmid (circular DNA of bacteria i.e. E. Coli).

Something called a restriction enzyme is used to 'cut' the plasmid of the bacteria to make room for the DNA coding for insulin, to fit into the plasmid. Restriction enzymes cut at specific sites and leave what are known as 'sticky ends'. It is the sticky ends that the DNA strand coding for insulin attaches to (by complementary base pairing - forming hydrogen bonds).

Then, another enzyme called DNA ligase is used to basically seal the new piece of DNA to the plasmid as DNA ligase catalyses the reaction to form the sugar-phosphate backbone of the DNA molecule.

Some of this stuff is most probably way too high for your exam, so if you don't understand some of it (some is quite tricky), check that its not on your specification. The specification for your exam can be found on the exam boards website.

I have tried to explain the process as simply as I can without it being too vague! But if its too complicated, tell me and I'll try and make it simpler and aimed more at your spec. as I have no idea what spec. your on.

If you have any more concerns with biology, contact me and I'll try and help you as best I can.

Good Luck

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