How is gene cloning done in transgenic animals?

Answer 1

The general idea is this - for any gene to be expressed it requires to be activated. A gene is activated by the correct messengers binding to an area upstream of the gene called a promoter. In transgenic animals, the gene of interest (reporter) is fused with the promoter of a gene that would express its protein in a region that can easily be extracted. They identify the gene by analysing the amino acid sequence of the protein then using an artificial copy of corresponding DNA radioactively tagged, they find the gene on the particular chromosome. The gene is introduced into the host animal by various techniques including micro injection. It is injected into a fertilised egg just prior to the first division so that as mitosis continues, all the cells of the organism will contain a copy of this gene. Including the cells that form the tissue that will secrete the protein of interest. If Human Insulin was to be produced from cows, then the Insulin reporter would be fused to a lactoglobin promotor found in mammary tissue. Thus the cow, when stimulated normally to produce lactoglobin, instead her new gene sneakily expresses insulin which is harvested from her milk.

This is a vast subject that requires some specialist knowledge hence a brief answer

Answer 2

Transgenic animals are animals produced with externally introduced genes. Transgenic animals can be used in many fields and as models to test the effect of certain genes on health. They can be used to produce "enhanced" versions of an animal.

They can also be used as bioreactors: animals that produce an extra substance we want. Imagine having a transgenic cow that is modified to produce insulin in large quantities in its milk. This insulin can then be purified from the cows milk and used in replacement therapy for treating patients with diabetes mellitus.

Embryonic stem cells (ES cells) are derived from the inner cell mass of blastocysts (early embryos). These cells are pluripotent, which means that they can develop into almost any type of tissue. ES cells are used for more precise modifications of the mouse genome. This technique makes it possible to insert as well as remove or modify DNA sequences. Knock-out, knock-in and conditional mutant mice [7] can be produced with this method. The first step is the removal of ES cells from a blastocyst. After transfection of the ES cells, selection, cloning and screening methods make it possible to detect ES cell clones that demonstrate the desired, site-specific recombination. After microinjection of the genetically modified ES cells into blastocyst-stage embryos the ES cells divide and become part of the embryo. The following chimeric animals will subsequently transmit the recombinant genotype to their offspring, if the ES cells have contributed to their germ cells.

Answer 3

Phew!