Nucleic acids

  • 30 янв. 2011 г.
  • 490 Слова
NUCLEIC ACIDS

 Nucleic acids differ from other organic molecules in their function.

• Genetic information is stored in nucleic acids. The unit of nucleic acids is nucleotide


••

• A nucleotide contains;
• 1- A pentose sugar,
• 2- A phosphate group, 3- A nitrogenous base.

Pentose sugars have 5 C atoms. There are 2 types of pentose. These are ribose anddeoxyribose.

Nucleic acids which contain ribose sugar are called ribonucleic acid or RNA.

Nucleic acids which contain deoxyribose sugar are called deoxyribonucleic acid or DNA.

All kindsof nucleotides have a phosphate group. It is identical in all types of nucleotides.

Phosphate group gives an acidic character to nucleotide.

Organic bases are nitrogen containing compounds.These are adenine (A), guanine (G), thymine (T), cytosine (C) and urasil (U).

Nucleotides are classified according to its organic base. For example: Nucleotide which contains thymine is calledthymine nucleotide.

DNA

Store genetic information by replication of itself and provides genetic continuity (HERITANCE).

Regulation of metabolic activity of cell by ordering the synthesisof all proteins and enzymes.

DNA molecule contains two long chains of nucleotides. The nucleotides of each chain are connected by phosphodiester bond.

In this way nucleotides are attach toeach other to form one strand of DNA. The second strand is ordered according to the nucleotide order of the first strand.

When bonding of two DNA strands an adenine is always bonded to a thymine.There are double hydrogen bond between adenine and thymine(A=T).

Cytosine is always bonded to guanine. There are three hydrogen bonds between cytosine and guanine (C --- G).

The number ofadenine nucleotide in DNA is equal to the number of thymine nucleotide.

Therefore number of cytosine is equal to number of guanine nucleotide.

REPLICATION

Before the cell division...
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