Paper Topic:

Biology

DNA MOLECULE

Significance of Nitrogenous Bases in the Structure of a DNA Molecule

The monomers that make up nucleic acids are called nucleotides . Each nucleotide is composed of three parts . One part is a five-carbon sugar and linked to one end of the sugar in both types of nucleic acid is a functional group called a phosphate group . Third , at the other end of the sugar is one of a number of chemical units called nitrogenous bases (since they all contain nitrogen

The four nitrogenous bases in a DNA molecule are

Adenine

- is an essential part of a DNA molecule , and is one of the purine (having six rings connected to five rings ) nucleobases . As it unites with thymine , adenine help stabilize the nucleic acid structures

Thymine - is a pyrimidine nucleobase and together with adenine , thymine also helps stabilize the nucleic acid structures

Cytosine - is also part of the pyrimidine family , composed of one ring It is characteristically unstable . A derivative of cytosine plays an important part in the metabolism of cells . It is closely engaged in the maintenance and continuation of genetic information ( Cytosine

Guanine - composed of two rings , it is part of the purine family . As it pairs with cytosine , guanine is actively involved in the perpetuation of genetic information ( Guanine

How the Nucleotides Bond

The DNA molecule is a lengthy chain polymer , naturally existing in two chains of paired nucleotides . These pairing are dictated by specific patterns . Two polynucleotides wrap around each other , with the nitrogenous bases protruding from the two sugar-phosphate backbones into the center of the helix . They always pair up with adenine characteristically pairing with the molecule thymine on one side of a DNA strand . On the other strand , guanine is usually pairing with cytosine . The two DNA chains are held in a double helix by hydrogen bonds between their paired bases . It is such pairing which gives the DNA molecule its double-helix structure , somewhat similar to a spiral staircase . The nitrogenous bases can be likened to the rungs of the stairs while the phosphate and sugar make up the steps . Most DNA molecules are very long , with thousands or even millions of base pairs One long DNA molecule contains many genes , each a specific series of hundreds or thousands of nucleotides along one of the polynucleotide strands . The chain in which the bases are linked is established through its DNA sequencing . The specific sequence of nucleotides in a gene is the information that programs the primary structure of a protein (Campbell , Mitchell Reece . Nucleic Acids

Evidence of Hereditary Instructions

The sequencing of the four bases along the sugar-phosphate backbone determines the set of information read by means of the genetic code . The stored information which is encapsulated in a storage molecule ' can be the basis of characteristics stored in a gene . The flow if information from gene to protein is based on a triplet code : The genetic instructions for the amino acid sequence of a polypeptide chain are written in DNA and RNA...

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