Yeast artificial chromosomes (YACs) are engineered yeast chromosomes containing megabase-sized fragments of foreign DNA. YACs are created by ligating bacterial plasmid DNA containing yeast centromeres, telomeres, and replication origins to fragments of genomic DNA. This creates an artificial yeast chromosome capable of replicating inside yeast cells and accommodating very large DNA inserts of up to 2 megabases. YACs can be used to generate whole genome libraries for mapping genes and identifying chromosomal sequences important for constructing mammalian artificial chromosomes. However, YACs are less stable than bacterial artificial chromosomes and prone to rearrangements due to their large insert sizes.

1. Yeast artificial chromosome & YAC VECTOR
Manish raj

2. WHAT IS
YACs
Vector?

3. Yeast artificial chromosomes (YACs) are genetically
engineered chromosomes derived from the DNA of the
yeast, Saccharomyces cerevisiae, which is then ligated
into a bacterial plasmid.
First described in1983 by Murray and Szostak
YACs are the largest capacity Yeast vectors,
accommodating megabase range (0.2 to 2 Mb) foreign
DNA fragments within Yeast Cell.

4. Plasmids (5 Kb)
Lambda Phage (20 Kb)
Cosmids (40 Kb Inserts)
P1 Vectors (100 Kb Inserts)
PACs (120 Kb Inserts)
YACs (0.2 Mb–2 Mb Inserts)
CLONNING CAPACITY

5. YAC is an artificially constructed chromosome that
contains a
Centromere
Telomeres
Autonomous replicating sequence (ARS) element
required for replication and preservation of
YAC in yeast cells.
YAC cloning vehicles are plasmids
Final chimeric DNA is a linear DNA molecule with
telomeric ends: Artificial Chromosome

6. Telomere
Selective Marker
BAMPICILLIN
RESISTANCE
ARS (Replications
origin)ARS1
Centromere
CEN4
Selective Marker
AURA3
Telomer
e
EcoRI Cloning site
BamHI
YEAST
CHROMOSOME
VECTOR
(YAC VECTOR)
BamHI
D i g e s t i o n w i t h B a m H I

7. D i g e s t i o n w i t h E c o R I
Fragments of Genomic DNA by
light digestion with EcoRI (Target
DNA)
telomere
telomere
telomere
telomere
Ligase
SelectablemarkerB
SelectablemarkerA
Cloning
site

8. YAC Transform
Yeast Cell Yeast Spheroplast Yeast with YAC done
Enzymatic
digestion of cell
wall
Select for
A& B

9. GROUPS OF
YACs
Vector

10. BASED ON THE MODE OF REPLICATION
Yeast Integrating
plasmids (YIp)
These plasmids
lack an ORI and
must be integrated
directly into the
host chromosome
via homologous
recombination.
Yeast
Centromere
plasmids (YCp):
These are considered
low copy vectors and
incorporate part of an
ARS along with part of a
centromere sequence
(CEN). These vectors
replicate as though they
are small independent
chromosomes and are
thus typically found as a
single copy. Unlike the
ARS vectors, CEN
vectors are stable
without integration.
Yeast Episomal
plasmids (Yep)
These are most similar
to bacterial plasmids
and are considered
“high copy”. A fragment
from the 2 micron circle
(a natural yeast
plasmid) allows for 50+
copies to stably
propogate per cell. The
copy number of these
vectors can also be
controlled if specific
regulatable elements
are included

11. OF
APPLICATIONS
YACs VECTOR

12.  generating whole DNA libraries of the genomes of higher
organisms to identifying essential mammalian chromosomal
sequences necessary for the future construction of
specialized Mammalian Artificial Chromosomes (MACs)
 Useful in the study of molecular genetics and
molecular cytogenetics
 Useful in gene mapping, FISH(in situ hybridisation)
banding, determination of chromosomal
breakpoints.

13. OF
DISADVANTAGES
YACs VECTOR

14.  Though the principle of cloning is similar to plasmid or
cosmid, but the process of cloning is too complicated to
carry out.
 It is difficult to isolate YAC DNA from host cell because of
its smaller size to host chromosome. Even higher yields
cannot be obtained.
 However, YACs are significantly less stable than
BACs, producing "chimeric effects“
 YACs harbor very large sized insert which is prone
to breakage resulting in rearrangement and
recombination with other DNA in host cell.

15. Thank
You