Introduction to RNA
- Helps in gene expression.
- Specify the amino acid sequence of a functional protein.
- Carries information from DNA to the ribosome.
- The process of forming mRNA on a DNA template is called transcription.
Note: a) If mRNA codes for only one polypeptide: Monocistronic ( In Eukaryotes).
b) If mRNA code for two or more than two polypeptides Polycistronic
General Properties of Nucleic Acids
- Double helical DNA and RNA can be denatured.
a. Disruption of hydrogen bond causes unwinding of double helical structure( also called Partial denaturation).
b. When the temperature or pH is returned to the real stand, the two strands spontaneously rewind to yield an intact duplex ( also called renaturation).
Renaturation occurs in two steps.
- Two strands find each other by random collision and form a short segment of complementary double helix.
- The unpaired base pair changes to a paired base pair and the two strands ‘zipper’ themselves to form a double helix.
c. Viral or bacterial DNA molecules in solution denature when they are heated slowly. i.e. the higher the content of the C≡ G base pair, the higher the melting point of DNA.
2. Nucleic acids from different species can form hybrids. Human DNA hybridizes much more extensively with mouse DNA than with yeast DNA.
3. Nucleotides and Nucleic acids undergo non-enzymatic transformations.
a. Purine and pyrimidines undergo a no. of spontaneous alterations in their covalent structures.
b. Hydrolysis of the N-glycosyl bond between the base and pentose occurs at a higher rate for purine than for pyrimidine.
c. Depurination of ribonucleotide and RNA is much slower.
