Artificial chromosomes are engineered DNA molecules that can stably maintain large DNA fragments like natural chromosomes. There are four main types: yeast artificial chromosomes, bacterial artificial chromosomes, human artificial chromosomes, and mammalian artificial chromosomes. Yeast and bacterial artificial chromosomes are used to clone large DNA fragments up to 500kb and 30kb respectively. Human and mammalian artificial chromosomes are engineered to act as entirely new chromosomes in human and other mammalian cells, carrying exogenous genes for applications like gene therapy.

1. Indira Gandhi Krishi Vishwavidyalaya
BTC CARS,BILASPUR
Presentation on-
Artificial chromosome and its uses
Submitted to
Mr.Roshan Parihar
Asst.Prof.
Deptt. Of Genetics & Plant
Breeding
Submited by
Dhanendra Dhanuka
M.Sc.(Pre) Genetics and
Plant Breeding

2. Artificial Chromosome
 Artificial chromosomes are DNA molecules assembled in
vitro from defined constituents, which gaurantee stable
maintenance of large DNA fragments with the properties
of natural chromosomes.
 Artificial chromosomes are useful for genome
sequencing programmes, for functional characterization
of entire genomic regions and for the transduction of
large DNA segments into human and non human
mammalian cells.

3. Types of Artificial Chromosomes
 There are four types of artificial chromosomes.
 They are:
1. Yeast artificial chromosome
2. Bacterial artificial chromosome
3. Human artificial chromosome
4. Mammalian artificial chromosome

4. Yeast artificial chromosomes
 D.T.Burke and G.F.Carle developed in the laboratory of
M.V.Olson an altogether new type of yeast vector called
yeast artificial chromosome.
 Yeast artificial chromosomes are genetically engineered
chromosomes derived from the DNA of the yeast,
Saccharomyces cerevisiae, which is then ligated into a
bacterial plasmid.
 Yeast artificial chromosome (YAC) vectors allow the
cloning, within yeaast cells, of fragments of foreign
genomic DNA that can approach 500kbp in size.

6. Construction of YAC
 A YAC is built using an initial circular DNA plasmid,
which is typically cut into a linear DNA molecule
using restriction enzymes; DNA ligase is then used
to ligate a DNA sequence or gene of interest into
the linearized DNA, forming a single large, circular
piece of DNA.

7. Bacterial artificial chromosome
 A bacterial artificial chromosome (BAC) is a DNA construct,
based on a functional fertility plasmid (or F-plasmid), used
for transforming and cloning in bacteria, usually E.coli.
 They are capable of carrying approximately upto 30kbp of
inserted DNA sequence.

9. Common gene components in BAC
 RepE: for plasmid replication and regulation of copy number.
 parA and parB: for partitioning F plamid DNA to daughter cells
during division and ensures stable maintenance of the BAC.
 Selectable marker: for antibiotic resistance; some BACs also have
lacZ at the cloning site for blue/ white selection
 T7 & Sp6: phage promoters for transcription of inserted genes.

10. Human artificial chromosome
 A human artificial chromosome (HAC) is a
microchromosome that can act as a new chromosome in a
population of human cells.
 That is, insted of 46 chromosomes, the cell could have 47
with the 47th being very small, roughly 6-10 megabases
(mb) in size instead of 50-250 mb for natural chromosomes
and able to carry new genes introduced by human
researchers.
 Ideally, researchers could integrate different genes that
perfom a variety of functions, including disease defense.

11. Construction methods of HAC
 There are currently two accepted models for the
creation of human artificial chromosomes.
- top – down approach (engineered chromosome)
- bottom up approach (de novo aritficial chromosome)
 The generated HACs are 1-10 mb in size, consisting
of multiple copies of rearranged input DNA molecules

12. Mammalian artificial chromosome
 Chromosomes in eukaryotes have evolved as vehicles for
nuclear genes and have developed specialized
nucleoprotein structures for this purpose, some of them are
centromeres, telomeres and origin of replication.
 They have been considered the best candidate for the
specific DNA requirement for centromere function.
 Alphoid rays are found at all human centromeres and
consist of a 171 bp monomer organized in higher order
repeats encompassing 0.5-5 mb.

13. Applications
 Applications of BACs
1. BACs have been used to study neurological
diseases such as Alzheimer's or as in case of
aneuploidy associated with Down syndrome.
2. BACs are often used to sequence the genome of
organisms in genome projects.

14.  Applications of YACs
1. Physical maaping
2. Chromosome walking

15.  Applications of HACs
1. HACs have been used to create transgenic animals
for use as animal models of human disease and for
production of therapeutic products.
2. HAC can carry genes to be introduced into the cells
in gene therapy.