Degeneracy, Universality and RNA

Year Ten
How RNA differs from DNA, plus explanations of the terms "Degenerate" and "Universal"

 

The term "degenerate", when used in the context of genetics, means that a part of a genetic code is redundant. Degeneracy in DNA is caused by the fact that the different combinations of nucleotides add up to make 64 potential codons, yet there are only 20 types of amino acid used to make proteins. The resultant codon : amino ratio of more than 3 : 1 means that there are often two or more redundant codons in each amino acid. The more redundant pieces of code, the more "degenerate" the code is said to be.

 

DNA is said to be "Universal" because all living things currently known to exist contain a DNA structure consistent of deoxyribose sugars, nitrogen bases and phosphates. Thought the order of bases within a sequence differs between organisms, the fundamental materials which make up a genetic code are the same throughout known life.

 

RNA stands for Ribonucleic acid. Like DNA, it is a polynucleotide chain made up of four nitrogen bases and phosphate groups. RNA differs from DNA in that the former normally exists as a single stranded molecule, with a short chain of nucleotides, whereas the latter's chain is longer and the molecule is always double stranded. The two also differ in terms of longevity: DNA is totally protected in the body cells and lasts so long as it can divide to reproduce. RNA, meanwhile, is repeatedly produced, destroyed and recycled. RNA does not replicate itself, but is manufactured in the body when necessary, based on existing DNA.

 

Chemically, one notable difference between DNA and RNA is that, though three bases (Adenine, Cytosine and Guanine) are common to both, the fourth changes between Thymine in DNA and Uracil in RNA. Another is that RNA uses Ribose sugars, whereas those in DNA are Deoxyribose - the difference being that deoxyribose lacks a single hydroxyl (OH) group present in ribose, replaced simply by hydrogen.

 

The purpose of DNA is to act as a medium for the long term storage of genetic information. RNA is only used for protein synthesis. mRNA is extracted from a DNA strand, and its codons are paired with the anticodons on a tRNA strand, resulting in an amino acid chain, rRNA then becomes part of the ribosome within a cell, which synthesise the proteins according to the code originally found in the DNA.

 

Sources: www.brighthub.com; www.bioinformatics.ni; www.enotes.com; www.buzzle.com

 

Originally written February 2013 by Robin Taylor. Scored at A

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