Salient Feature Of DNA || Salient Feature of RNA ||

 

Fig: DNA

  Nucleic acid are present mainly within the nucleus in every living cell. These are complex molecules having very high molecular weight.  These are two distinct types of nucleic acid which is called DNA or deoxy ribonucleic acid which  is exclusively found in the nucleus. The other is ribonucleic acid or RNA. Some RNA is also found in nucleus but most of them are present in cell cytoplasm




Salient features of DNA and RNA:-

  Except in mitochondrial DNA occurs mainly within the nucleus. It is usually double stranded except some viral DNA with single stranded DNA is found. It consists of two polynucleotide chains where the sugar and phosphate group form the backbone and the nitrogenous bases project inside the helix. Generally it contains a large number of nucleaotides up to 4.5 million and the pentose sugar is deoxyribose. The two polynucleotide chains have anti-parallel polarity i.e. if one strand has 5′ → 3′ polarity, the other strand has 3′ → 5′ polarity.

  The bases on the opposite strands are connected through hydrogen bonds forming base pairs (bp). These nitrogenous based are Adenine, Guanine, Thymine & Cytosine. Adenine always forms two hydrogen bonds with thymine from the opposite strand and vice-versa. Guanine forms three hydrogen bonds with cytosine from the opposite strand and vice-versa. Therefore, a purine always pairs with a pyrimidine on the other strand, giving rise to a uniform distance between the two strands of the helix. The helix is stable because of the base pairs that stack over one another and hydrogen bonds that hold the bases together.

   On replication, DNA forms daughter DNA and transcription it from RNA. The genetic messages are usually encoded in DNA and except in some viruses it is the main genetic material of all organism.


Fig: RNA

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  Salient Feature of RNA:-

 it is present mainly within the cytoplasm. mRNA is also found in nucleus .RNA molecules are mainly single-stranded some viral mRNA may have told to give its clover leaf like appearance. The RNA consist fewer nucleotides upto 12000. Generally in RNA, the pentose sugar is ribose. The nitrogenous bases are some with DNA except that thymine is replace by uracil. There are generally three types of RNA ie. messenger RNA, ribosomal RNA and transfer RNA. The RNA does not replicate. It synthesize from DNA. It is the genetic material in some viruses and it takes part in protein synthesis and the specific messages for protein synthesis is usually encoded in RNA



*Additional Point: The two strands coil in a right-handed fashion. Each turn of the helix is 3.4nm (or 34 Angstrom units) consisting of 10 nucleotides. These nucleotides are at a distance of 0.34nm (or 3.4 Angstrom units).




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