Vectors are small pieces of DNA that can accept foreign DNA and be maintained within an organism. Common vectors include plasmids, bacteriophages, and artificial chromosomes. Plasmids are circular DNA molecules that can replicate independently of the bacterial chromosome. Bacteriophages infect bacteria and have been engineered as vectors. Vectors allow for cloning of DNA fragments to study genes and their functions.
2. A vector is a small piece of DNA taken from a virus or
a plasmid or the cell of a higher organism that can be
stably maintained in an organism and into which a
foreign DNA fragment can be inserted for cloning
purposes.
3. • Ability to promote autonomous replication.
• Contain a genetic marker(usually
dominant)for selection.
• Unique restriction sites to facilitate cloning
to insert DNA.
• Minimum amount of non-essential DNA to
optimize cloning.
5. Plasmid is a circular, double stranded,
non-essential, extra-chromosomal DNA which co-
exist with chromosomal substances and can
replicate autonomously as a stable component of
cell’s genome.
6. • BASED ON FUNCTION
1. FERTILITY OR F PLASMID: They contain the tra gene. They
are capable of conjugation and result in the expression of
sex pilli.
2. RESISTANCE OR R PLASMID: They make the host cell
resistant to one or more antibiotics and many R plasmids
can transfer the resistance to cells lacking R.
3. COLICINOGENIC OR Col PLASMID: It synthesizes the protein
COLICIN, that can kill closely related bacterial strains that
lack a Col plasmid of the same type.
4. VIRULENCE PLASMID: They make the host of the plasmid
into a pathogen.
7. A plasmid can be considered a suitable cloning vehicle if it
possesses the following features:
• It can be really isolated from the cells,
• It possesses a single restriction site for one or more
restriction enzyme(s),
• Insertion of a linear molecule at one of these sites does
not alter its replication properties,
• It can be reintroduced into a bacterial cell and cells
carrying the plasmid with or without the insert can be
selected or identified (Bernard and Helinski, 1980),
• They do not occur free in nature but are found in
bacterial cells
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11. Virus that infect bacteria is known as bacteriophage.
D’ Herelle coined the term bacteriophage meaning
‘bacterial eater’ to describe the agent’s bacteriocidal
activity.
Phages are very simple in structure, consisting merely
of a DNA (or occasionally ribonucleic acid (RNA))
molecule carrying a number of genes,surrounded by a
protective coat or capsid made up of protein molecules.
12. Bacteriophage vectors are used because they have
following advantages over the plasmids:
• DNA can be packed in vitro into phage particles and
transduced into E. coli with high efficiency.
• Foreign DNA upto 25 Kb in length can be inserted into
phage vector.
• Screening and storage of recombinant DNA is easier
(Dahl et al, 1981).
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15. Fig : Cloning of an insertion vector. Fig : Cloning of a replacement vector.
16. • A particular gene can be isolated and its nucleotide
sequence be determined.
• Genomic library construction.
• Preparation of probes.
• Control sequences DNA can be identified and
analysed.
• Protein/enzyme/RNA function can be investigated.
• Mutations can be identified e.g: gene defects
related to specific diseases.
• Organism can be “engineered” for specific purposes
e.g: Insulin production.
17. • Improved Medicines
• Improved Livestock (resistance to disease)
• Improved Crops (resistance to disease, higher yields)
• Prevention of Genetic Diseases
• Lowering the cost of medicines (i.e. Insulin)
• Safer Medicines (i.e. Insulin)
• Treatment for pre-existing conditions
