4.4.7 & 4.4.8: Gene TransferAnthony Almazan & Sandhya Jetty

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.

4.4.7

The Genetic Code

•Genetic code: Determines how genetic material is translated into proteins.

•The genetic code consists of 64 triplets of nucleotides.

•Codon: An mRNA base triplet that encodes for a specific amino acid.

•Redundancy: Multiple codons can code for the same amino acid

•No ambiguity: Each codon can only specify one amino acid.

Universality of the Genetic Code

The genetic code is nearly universal

• In almost all organisms, every codon will be translated as the same amino acid.

• Exceptions: There are variations in the genetic codon in certain unicellular eukaryotes and organelle genes.

Significance

• The near universality of the genetic code allows for gene transfer and transplantation between different species.

Applications and Ethics of Gene Transplantation

Purpose of Genetically Modifying Animals

To identify, isolate, and characterize genes in order to understand their function.

To provide research models of human genetic diseases and help develop new strategies for gene therapy.

To provide organs and tissues for use in human transplant surgery.

To alter composition of food to improve its nutritional value.

To enhance livestock improvement programs.

Ethical Concerns

Animal sentiency

Affecting animal welfare

Outline a basic technique used for gene transfer involving plasmids, a host cell (bacterium, yeast or other cell), restriction enzymes (endonucleases) and DNA ligase.

4.4.8

Terminology

• Gene transfer• Horizontal gene transfer: process in which an

organism incorporates genetic material from another organism without being the offspring of that organism

• Vertical gene transfer: process in which an organism receives genetic material from its ancestor

• Plasmid: Small, circular DNA molecule used to transfer genes from one organism to another comprised of 2-30 genes of bacterial DNA• Found mostly in bacteria• Act as vectors, the medium to transfer foreign

genetic material into the host cell• Host cell: A cell that has been infected with a virus

• Restriction enzyme: A protein isolated from bacteria that recognizes specific DNA sequences and cuts the DNA at those sites

• DNA Ligase: Enzyme that catalyzes the reconnection of the 2 fragments of DNA by creating covalent bonds

General Method of Gene Transfer

1. The plasmid is removed from the host cell.

2. The plasmid is cleaved by endonuclease, producing “sticky ends, short sequences of unpaired bases at the end of the DNA.

3. The genes and DNA fragments from another organism are cleaved by the same endonuclease, producing complementary sticky ends.

4. DNA ligase catalyzes the reconnection of the 2 different fragments of DNA.

5. The recombinant plasmid is inserted into the host cell.

6. The desired gene product is attained.

Gene Transfer Example: Harvesting Insulin

1. Messenger RNA coded for insulin is extracted from the human pancreas cell.

2. Reverse transcriptase, an enzyme, makes copies of messenger RNA.

3. Plasmids are cut open using endonuclease.

4. DNA ligase joins the insulin gene and the plasmid together, as their sticky ends are complementary.

5. The insulin gene and plasmid form a recombinant plasmid.

6. The recombinant plasmid is mixed with a strain of E. coli.

7. The E. coli begin producing insulin which is later extracted and purified so it can be used for patients suffering from diabetes.

Works Cited

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Hurlbert. "Ligase Animation." Washington State University. Web. 26 Feb. 2011. <http://www.slic2.wsu.edu:82/hurlbert/micro101/images/LigaseAnimation6.gif>.

Kimball, John W. Biology. Reading, MA: Addison Wesley Pub., 1983. Print.Sobey, B. "Recombinant DNA (rDNA): Technology, Plasmids, and Resources." The

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<http://www.thefreeresource.com/recombinant-dna- rdna-technology-plasmids-and-resources>.

Straughan, R. "Ethics, Morality and Animal Biotechnology." University of Worcester. Web. <www.worc.ac.uk/graduateschool/documents/BBSRC_animal_ethics.pdf>.