Yeast artificial chromosomes (yac)

[aayush_005]

Plasmid can accommodate about 10 kb foreign DNA, phage A can accommodate about 20 kb DNA insert, cosmid can accommodate about 40 kb long four DNA segments. It was realized that for stable replication and segregation in eukaryotes, particularly in yeast, a small and well defined sequence should be constructed as recombinant chromosome.
With this objective David and co-workers developed, in 1987, yeast artificial chromosomes (YAC) by using new approaches where DNA segment of several thousand base pairs (about I Mb) can be cloned. Initially it was used for investigation of the maintenance of chromosomes in the cell. Later on it was used as vectors for carrying very large cloned fragments of DNA. It has also been used for physical mapping of human chromosome in 'Human Genome Project’.
A typical YAC consists of centromere element (CEN) for chromosomal segregation during cell division, telomere, and origin of replication (ori) were isolated and joined on plasmids constructed in E. coli. Structure of typical YAC3 vector is shown in Fig.
The YAC3 vector contains the E. coli origin of replication (oriE) and a selectable marker (amp'), a yeast DNA sequence, genes each for uracil biosynthesis pathway (URA3) providing centromeric function (CEN), autonomously replication sequence (ARS) (which acts as yeast ori), tryptophan synthesis pathway (TRP) and telomeric (T) sequence (which is extended by the enzyme telomerase inside the yeast cell) (Fig).
The TRP 1 and URA3 are yeast selectable markers, one for each end, which ensure that properly reconstituted YACs survive in yeast cells, Sup4 is inactivated in recombi-nants and acts as a basis for red-white selection unlike blue-white selection in E. coli. There are recognition sites for restriction enzymes such as Smal and BamHI.
For cloning purpose, YAC is digested with restriction enzyme (BamHIII and EcoRI) and recombinants are produced by inserting a large fragment of genomic DNA. This molecule can be maintained in yeast as YAC. The transformants that contain YAC can be identified by red/white colour selection. Non-transformed yeast contain white colonies. Red colonies of yeast contain recombinant YAC molecules. Due to insertion of DNA molecule into EcoRI site, Sup4 gene is inactivated and no protein will be expressed. This facilitates to develop red colonies.

[alexseinicolaev]

Hello, dear colleagues. Sorry that it was not on site Testforum.com writing.
Wea'can please where to get the key or breaking a toy Farm Frenzy 3 & Farm Frenzy 2 though-be?
Kids games very much, but they were not complete and is now asking the keys. All Internet searched, working crack and the key to the game not found!
'll Show where to get or buy at a reasonable price. Write please on the forum or on my mail granitss@mail.ru
Sincerely Alexey.

[alenachka]

Hello everyone! Who knows where to upload the film Avatar?
I even bought the film Avatar for a SMS to http://rsskino.ru/kinofilm/avatar.html , the link was, but download fails, the system will boot quite strange cocoa something.
Men, advise where to normal as quickly download film avatar?