(a) Plasmid DNA is naked double stranded DNA that forms a
circle with no free ends. It is associated with few proteins but contains RNA
polymerase enzymes. It is smaller than the host chromosome and can be easily
DNA is double stranded linear DNA molecule associated with large proteins. This
DNA exists in relaxed and supercoiled forms and provides a template for
replication and transcription. It has free ends represented as .
Differences between exonucleases and endonucleases are as follows:
These nucleases cleave base pairs of DNA at their
They cleave DNA at any point except the terminal
They act on single strand of DNA or gaps in
double stranded DNA.
They cleave one strand or both strands of double
They do not cut RNA.
They may cut RNA.
It usually occurs inside nucleus and some cell
Very little RNA occurs inside nucleus. Most of it
is found in the cytoplasm.
DNA is the genetic material.
RNA is not the genetic material except in certain
viruses, e.g., Reovirus.
It is double stranded with the exception of some
viruses (e.g., x
RNA is single stranded with the exception of some
viruses (e.g., double stranded in Reovirus).
It is long lived.
Some RNAs are very short lived while others have
somewhat longer life.
It contains deoxyribose sugar.
It contains ribose sugar.
Nitrogen base thymine occurs in DNA along with
three others ? adenine, cytosine and guanine.
Thymine is replaced by uracil in RNA, The other
three - adenine, cytosine and guanine are similar.
Unusual bases are very few or absent.
Many unusual or modified bases are often present.
Hydrogen bonds are formed between complementary
nitrogen bases of the opposite strands of DNA (A-T, C-G).
Base pairing through hydrogen bonds occurs only
in the coiled parts.
DNA is spirally twisted to produce a regular
The strand may get folded at places to produce a
secondary helix or pseudo helix.
It replicates to form new DNA molecules.
It cannot normally replicate itself.
DNA transcribes genetic information to RNA.
RNA translates the transcribed message for
Its quantity is fixed for cell.
The quantity of RNA of a cell is variable.
Purine and pyrimidine bases are in equal number.
There is no proportionality between number of
purine and pyrimidine bases.
It occurs in the form of prochromosome, chromatin
It occurs in ribosomes or forms association with
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