4.4. Genetic Engineering and Biotechnology

4.4.7 to 4.4.8 Part 2

4.4.7 State that, when genes are transferred between species, the amino acid sequence of polypeptides translated from them is

unchanged because the genetic code is universal

• Genetic engineering refers to the deliberate manipulation

• It is possible to move genetic material between species because the genetic code is universal. This means that, for every organism, the same RNA codon codes for the same amino acid in an mRNA strand.

• UUU and UUC both code for the amino acid phenylalanine while CUU, CUC, CUA, and CUG all code for leucine, regardless of the species.

Genetic code is Universal

• Since the genetic code is universal, it is possible to transfer genetic material from one species to another. Because the code is universal, it is possible to introduce a human gene for making insulin into a bacterium.

• The bacterium will then produce the human protein hormone insulin, which is responsible for making cells take up more glucose and convert it to glycogen.

Gene Transfer

• The technique of taking a gene out of one organism ( the donor organism, e.g. a fish) and placing it in another organism ( the host organism, e.g. a tomato) is a genetic engineering procedure called gene transfer.

• Such a transfer was done to make tomatoes more resistant to cold and frost.

Gene Transfer

• It is possible to put one species’ gene into another’s genetic make up because DNA is universal. In the example of tomatoes, proteins used by fish to resist the icy temperatures of arctic waters are now produced by the modified tomatoes to make them more resistant to cold.

• Another example of gene transfer is found in Bt-corn, which has been genetically engineered to produce toxins that kill the bugs which attack it.

Bt-Corn

• The gene, as well as the name come from a soil bacterium, Bacillus thuringiensis, which has the ability to produce a protein that is fatal to the larvae of certain crop-eating pests.

Questions to Ponder• Is it ethically acceptable to alter an organism’s genetic integrity?• If the organism did not have the gene in the first place, could there

be a good reason for its absence?• Why are people so worried about this new technology? In selective

breeding, thousands of genes are mixed and matched. With GMOs only one gene is changed. Is that not less risky and dangerous than artificial selection?

• Would strict vegetarians be able to eat a tomato which has a fish gene in it?

• Does research involving GM animals add a whole new level to animal cruelty and suffering in laboratories?

• If Bt—crops kill insects, what happens to the local ecosystem which relies on the insects for food for pollination?

4.4.8 Outline a basic technique used for gene transfer involving plasmids, a host cell (bacterium, yeast or other cell), restriction

enzymes (endonucleases) and DNA ligase

• Gene transfer involves the following elements:• A vector• A host cell• Restriction enzymes• DNA ligase• The vector is what is needed to carry the gene into the host cell.

Plasmids are often used as vectors.• Bacteria carry all the required genetic information on one large

circular DNA. However, most bacteria also possess extra DNA in the form of plasmids. Plasmids are bits of genetic material carrying 2-30 genes. Plasmids my replicate at the time the chromose replicates or at toehr times.

Steps in cloning a gene

• http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120078/micro10.swf::Steps%20in%20Cloning%20a%20Gene

• http://www.youtube.com/watch?v=d_YJZn-ft_Q

• Gene therapy video

Gene transfer in insulin production from abpi schools

• http://www.abpischools.org.uk/res/coResourceImport/modules/hormones/en-flash/geneticeng.cfm

The general technique of gene transfer

Technique of gene transfer

• Plasmids are used to clone a desired gene.• First you splice or introduce a desired gene into a

plasmid and transfer it into a bacterial cell.• Then, culture these bacteria; many of them will have the

plasmid with the desired gene.• Use a section of nucleotides, complementary to the

desired gene, but also attached to a (radioactive) label to find out which plasmids have the gene and which do not.

• Use restriction enzymes to cut the desired gene out of the plasmids and purify the gen using gel electrophoesis.

• The host cell is the cell which is to receive the genetic material. A bacterium may be the host cell and produce a protein desired by humans.

• Restriction enzymes (endonucelases) are used to cut a desired section of the DNA. Bacteria produce these enzymes naturally as a defense against invading viruses.

-• One commonly used restriction enzymes recognizes sequence

GATTC and cuts both strands of the DNA between G and A.• When preparing to transfer DNA, the same restriction enzyme is

used for the host and the donor so the cuts are made in the same way.

• This way, the same ‘sticky ends’ are created so that the donor DNA can fit in between the host DNA.

• The result is the uneven cut in the DNA and the ends of the DNA are referred to as “sticky ends”. If the same sequence is found on another section of DNA and is cut in the same way, the two strands can be combined.

• To attach the two cut sections of DNA, the enzyme DNA ligase is used to create the required covalent bonds.

Recombinant DNA