LECTURE 1: INTRODUCTION
Genetic engineering, recombinant DNA technology, genetic modification/manipulation (GM) and gene splicing are terms that apply to the direct manipulation of an organism's genes. It uses the techniques of molecular cloning and transformation to alter the structure and characteristics of genes directly.
Differences between DNA and RNA:
- Withthe exception of a few viruses, RNA is a single-stranded molecule while DNA is double-stranded.
- Both contain a sugar, phosphate groups and 4 different nitrogenous base pairs, 3 of which are the same for both RNA and DNA: guanine, adenine and cytosine. Thymine, the fourth base pair found in DNA, is replaced by uracil in RNA. Of the nitrogenous bases: adenine, and guanine are both purines, whichare bicyclic, while cytosine, thyamine and uracil are pyrimidines, which are cyclic rather than bicyclic.
- DNA has deoxyribose sugar while RNA has ribose sugar < This means that the Deoxyribose sugar is less in one oxygen atom than the Ribose sugar.
Differences between eukaryotic and prokaryotic cell:
1. Eukaryotic cells have a true nucleus, bound by a double membrane. Prokaryotic cells haveno nucleus. The central region of the prokaryotic cell is "nucleoid" (-oid=similar or imitating to nucleous). But note that the nucleoid is essentially an imaginary "structure." There is no physical boundary enclosing the nucleoid.
2. Eukaryotic DNA is linear; prokaryotic DNA is circular.
3. Eukaryotic DNA is complexed with proteins called "histones," and is organized intochromosomes. A prokaryotic cell contains only one circular DNA molecule and a varied assortment of much smaller circlets of DNA called "plasmids."
4. Both cell types have ribosomes, but the ribosomes of the eukaryotic cells are larger and more complex than those of the prokaryotic cell.
5. The cytoplasm of eukaryotic cells is filled with a large, complex collection of organelles, many of themenclosed in their own membranes; the prokaryotic cell contains no membrane-bound organelles which are independent of the plasma membrane.
Advantages and disadvantages:
The modification of the DNA structures of agricultural crops can increase the growth rates and even resistance to different diseases caused by pathogens and parasites. Genetic engineering can also increase the genetic diversityof species populations, especially those that are classified as being endangered. Disease could be prevented by detecting people/plants/animals that are genetically prone to certain hereditary diseases. Also, infectious diseases can be treated by implanting genes that code for antiviral proteins specific to each antigen.
Nature is an extremely complex inter-related chain consisting of manyspecies linked in the food chain. Introducing genetically modified genes may have an irreversible effect with consequences yet unknown. Genetic engineering borderlines on many moral issues.
Basic principles of GE:
Isolate the gene.
Insert it in a host using a vector (plasmid).
Modification or change our gene.
Produce as many copies of the host as possible. Transfer the organism to be modified.Separate and purify the product of the gene.
Suitable for addressing our questions.
short generation time
Easy to cultivate
with a good (known) genetic background
possibility of control pairings
the possibility of using genetic engineering.
Horizontal gene transfer:
Bacterial conjugation is the transfer of genetic material between bacteria through direct cell to cellcontact.
Transduction is the process by which DNA is transferred from one bacterium to another by a virus. It also refers to the process whereby foreign DNA is introduced into another cell via a viral vector.
Transformation is the genetic alteration of a cell resulting from the uptake, genomic incorporation, and expression of foreign genetic material.
Induced protoplast fusion