The YAC, defined by a high-capacity cloning (600-1400
kb) vector constructed from the components of a yeast chromosome, appeared when
it was necessary to create vectors that would be able to clone DNA fragments
longer than 50 kb.
This vector contains a centromere, telomeres and an
autonomous replicating sequence (ARS). These structures are important
requirements for replication and preservation of YAC in yeast cells. These vectors are propagated in Saccharomyces cerevisiae rather than in Escherichia coli and are
based on chromosomes, rather than on plasmids or viruses.
Currently, this vector has the highest
capacity of any type of cloning vector, and a lot of genome projects have used
it. Unfortunately,
with some types of YAC there have been problems with insert stability, the
cloned DNA becoming rearranged into new sequence combinations (Anderson, 1993). For this reason there is also great interest in
other types of vectors, ones that cannot clone such large pieces of DNA but
which suffer less from instability problems.
Bibliography:
Brown, T. A.,
2002, Genomes, 2nd ed., Oxford: Wiley-Liss.
Anderson, C.,
Genome shortcut leads to problems. Science. (1993);
259:1684–1687
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