Transgenesis

Transgenesis

Transgenesis is the set of techniques to transfer one or more genes from one organism said donor organism to a recipient organism called recipient organism, or even host organism, to obtain a genetically modified organism. To transfer this gene from one organism to another it passes through a vector often designed from the genetic program of a bacterium or virus.

So that transgenesis be possible, certain conditions are essential. First you should know that transgenics is made possible through the universality of genetic code. We must therefore ensure that the gene is introduced into the recipient organism fits well into the genome so that it can express. It must also be transmitted to the offspring.

To be successful transgenesis requires:

- Penetration of the transgene in the target cells

- son intégration dans le génome

- Its ability to expressing in the cells (protein production)

- And finally the possibility of obtaining the regeneration of whole individuals from genetically modified cells.

Bone marrow and immune system

What is the role of bone marrow?

Our bone marrow produces blood cells called red blood cells (erythrocyte), platelets and white blood cells (leukocyte).

In the bone marrow, blood cells begin their lives as young, immature cells called stem cells. Once they are developed, the blood cells do not live long. That is why our bone marrow continually produces three types of blood cells to keep us healthy.

Bone marrow and blood cells

- Red blood cells:

These cells are red because they are filled with a protein called hemoglobin. Oxygen and carbon dioxide bind to the iron that is hemoglobin, which allows the red blood cells to carry oxygen to the body. Red blood cells also rid the body of carbon dioxide, which leaves the body through the lungs when we exhale.

- Platelets:

Platelets are blood cells that help the blood to clot (by sticking together) to help stop the bleeding at the body that have been cut or injured. Platelets form of scabies that covers a small cut.

- White blood cells:

White blood cells help the body fight infections. There are many different types of white blood cells, including:

     - Lymphocytes, Neutrophils, and Monocytes: These white blood cells fight bacteria, viruses or fungi that invade the body to destroy infections. Each cell has a different appearance.

     - Eosinophils and Basophils: These cells react to allergies that can invade the body.

cDNA

What’s a cDNA :

It's the DNA copy of a mRNA without intron obtained by reverse transcriptase. cDNAs have no introns and can be expressed by the bacteria.

Synthesis of cDNA :

Manipulation and study of RNA is difficult because of their high sensitivity to ribonucleases that destroy, so :

- It is necessary to recopy the sequence to DNA to be more stable and that can be amplified as required.

- The purified mRNA (affinity chromatography on an oligo-d(T) column) is bonded at first with oligonucleotides poly (T) which will be attached to the poly (A) tail.

- From the 3 'end of this primer poly (T) the reverse transcriptase, which is a DNA polymerase, synthesizes a DNA strand complementary to the messenger of departure.

- Once completed this synthesis the RNA is degraded by a specific ribonuclease or by a strong base.

- The DNA strand made ​​spontaneously forms at its 3'end of a hairpin loop by hybridizing to itself.

- The 3 'end of the loop will serve as a site of start for the DNA polymerase which will synthesize a complementary DNA strand of the first.

- A specific nuclease of single-stranded DNA removes the loop from the end. The double-stranded cDNA is ready.

- Thereby we can constitute much of cDNA that it exists messengers in a cell: all of these cDNA form a «cDNA library».

 

Synthesis of cDNA