bio valium

Speed of DNA Replication
The Genome of complex eukaryotes is huge and the process of DNA Replication should be incredibly fast. It is amazing that a Chromosome of 250 million pair of bases can be replicated in several hours. The speed of DNA replication for the humans is about 50 nucleotides per second per replication fork (low speed comparing to the speed of the bacterial DNA Replication).But the human Genome can be copied only in a few hours because because many replication forks take place at the some time (multiple initiation sites)

The DNA Double Helix makes a complete turn in over 10 nucleotide pairs, so each turn takes 35.7 ?. About 25 hydrogen bonds are created in this complete turn. The power of these 25 bonds is equal to 1 covalent bond (bond between carbon and oxygen). The diameter of a DNA Double Helix is 20 ?. The length of the helix can be 2 cm (!!) if the helix is fully stretched.

DNA Double Helix


The hydrogen bonds and the bonds between deoxyribose and phosphates are the main (but not only) chemical forces that create a DNA Double helix (pic.2).

DNA Replication
One major question for the human mind is how life continues. One of the most important mechanisms for all life cells to give offsprings is undoubtedly the DNA Replication. DNA Replication answers to the question: "When a cell divides, where the extra DNA comes from?". What "DNA Replication" is? It is the process that can duplicate the DNA of a cell. The next step is the cell to duplicate!
n the eukaryotes (organisms with cell that have nucleus) the DNA is formed in two strands, each composed of units called Nucleotides. The two strands look like two chains that form the DNA Double Helix. The DNA Replication Process is capable of opening the Double Helix and separating the two strands. Then the two strands are copied. As a result two new DNA molecules are created. The next step is the cell division. After that a daughter cell is created. In its nucleus lies a copy of the parental DNA.

Follow the links in the left menu in order to find more info about the DNA Replication Process.

Geminin: negative control of replication

G2 nuclei also contain at least one protein — called geminin — that prevents assembly of MCM proteins on freshly-synthesized DNA (probably by blocking the actions of Cdt1).

As the cell completes mitosis, geminin is degraded so the DNA of the two daughter cells will be able to respond to licensing factors and be able to replicate their DNA at the next S phase.

The Enzymes

* A portion of the double helix is unwound by a helicase.
* A molecule of a DNA polymerase binds to one strand of the DNA and begins moving along it in the 3' to 5' direction, using it as a template for assembling a leading strand of nucleotides and reforming a double helix. In eukaryotes, this molecule is called DNA polymerase delta (δ).
* Because DNA synthesis can only occur 5' to 3', a molecule of a second type of DNA polymerase (epsilon, ε, in eukaryotes) binds to the other template strand as the double helix opens. This molecule must synthesize discontinuous segments of polynucleotides (called Okazaki fragments). Another enzyme, DNA ligase I then stitches these together into the lagging strand.

The Biochemical Reactions

* DNA replication begins with the "unzipping" of the parent molecule as the hydrogen bonds between the base pairs are broken.
* Once exposed, the sequence of bases on each of the separated strands serves as a template to guide the insertion of a complementary set of bases on the strand being synthesized.
* The new strands are assembled from deoxynucleoside triphosphates.
* Each incoming nucleotide is covalently linked to the "free" 3' carbon atom on the pentose (figure) as
* the second and third phosphates are removed together as a molecule of pyrophosphate (PPi).
* The nucleotides are assembled in the order that complements the order of bases on the strand serving as the template.
* Thus each C on the template guides the insertion of a G on the new strand, each G a C, and so on.
* When the process is complete, two DNA molecules have been formed identical to each other and to the parent molecule.

Gene therapy
Main article: Gene therapy
Gene therapy using an Adenovirus vector. A new gene is inserted into an adenovirus vector, which is used to introduce the modified DNA into a human cell. If the treatment is successful, the new gene will make a functional protein.

Gene therapy may be used for treating, or even curing, genetic and acquired diseases like cancer and AIDS by using normal genes to supplement or replace defective genes or to bolster a normal function such as immunity. It can be used to target somatic (i.e., body) or gametes (i.e., egg and sperm) cells. In somatic gene therapy, the genome of the recipient is changed, but this change is not passed along to the next generation. In contrast, in germline gene therapy, the egg and sperm cells of the parents are changed for the purpose of passing on the changes to their offspring.

There are basically two ways of implementing a gene therapy treatment:

1. Ex vivo, which means “outside the body” – Cells from the patient’s blood or bone marrow are removed and grown in the laboratory. They are then exposed to a virus carrying the desired gene. The virus enters the cells, and the desired gene becomes part of the DNA of the cells. The cells are allowed to grow in the laboratory before being returned to the patient by injection into a vein.
2. In vivo, which means “inside the body” – No cells are removed from the patient’s body. Instead, vectors are used to deliver the desired gene to cells in the patient’s body.

As of June 2001, more than 500 clinical gene-therapy trials involving about 3,500 patients have been identified worldwide. Around 78% of these are in the United States, with Europe having 18%. These trials focus on various types of cancer, although other multigenic diseases are being studied as well. Recently, two children born with severe combined immunodeficiency disorder (“SCID”) were reported to have been cured after being given genetically engineered cells.

Bio-Technology General Corp. The Group's principal activity is to conduct research, development, manufacture and marketing of biopharmaceutical products. The Group through the internal research, development and agreement has a portfolio of therapeutic products. The products include OXANDRIN (r), BIO-TROPINTM, BIOLON (r), DELATESTRYL (r), MIRCETTE (r) and others. OXANDRIN(R) is used for the treatment of weight loss due to severe trauma, chronic inflection, extensive surgery or unknown pathophysiology. BIO-TROPIN(TM) for the treatment of growth hormone deficiency in children or turner syndrome. BIOLON (R) is used for the protection of the corneal endothelium during ophthalmic surgery. DELATESTRYL (R), for the treatment of hypogonadism and delayed puberty. On 30-Sep-2002, it acquired Rosemont Pharmaceuticals Ltd. During the year 2001, the Group acquired Myelos Corporation. Product sales accounted for 97% of 2002 revenues; Contract fees, 2% and Other revenues, 1%.