(i) Plasmids and Cosmids
Plasmids: These are the extra-chromosomal, independent, self replicating, circular double stranded DNA molecules naturally found in all bacteria and some fungi.
Cosmids : These are predominantly plasmids with a bacterialori, an antibiotic selection marker and a cloning site, but they carry one or more recently two ‘cos’ sites derived from bacteriophage lambda.
(ii) Nucleotide and Nucleoside:
Nucleotide:
Nucleotide is a condensation product of heterocyclic nitrogen base, a pentose sugar like ribose or deoxyribose, and a phosphate or polyphosphate group.
Nucleoside:
Nucleoside consisting of a pentose sugar, usually ribose or deoxyribose, and a nitrogen base purine or pyrimidine.
(iii)Lagging strand and Leading strand
Lagging strand:
1. Lagging strand is a replicated strand of DNA which is formed in short segments called Okazaki fragments. Its growth is discontinuous.
2. DNA-ligase is required for joining Okazaki fragments.
Leading strand:
1. It is a replicated strand of DNA which grows continuously without any gap.
2. It does not require DNA ligase for its growth.
(iv) Multipotent cells and Unipotent cells
Multipotent Cells:
Multi potent cells have the ability to differentiate into many of the various types of specialized cell types and can develop into any cell of a particular group or type, e.g., Umbilical cord stem cell
Unipotent Cells:
Uni potent cells can undergo unlimited reproductive divisions, but can only
differentiate into a single type of cell or tissue.
e.g., Skin cells.
(v)Microinjection and biolistic
Microinjection:
In this technique foreign DNA is directly and forcibly injected into the nucleus of animal and plant cells through a glass micropipette containing very fine tip of about 0.5 mm diameter. It resembles with injection needle.
Biolistic:
In this technique macroscopic gold or tungsten particles are coated with desired DNA. The particles are bombarded onto target cells by the bombardment apparatus. Consequently foreign DNA is forcibly delivered into the host cells.
