Scientists Discover Parallel Codes In Genes

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Scientists Discover Parallel Codes In Genes

http://www.sciencedaily.com/releases/2007/02/070208230116.htm

Researchers from The Weizmann Institute of Science report the

discovery of two new properties of the genetic code. Their work,

which appears online in Genome Research, shows that the genetic

code -- used by organisms as diverse as reef coral, termites, and

humans -- is nearly optimal for encoding signals of any length in

parallel to sequences that code for proteins. In addition, they

report that the genetic code is organized so efficiently that when

the cellular machinery misses a beat during protein synthesis, the

process is promptly halted before energy and resources are wasted.

" Our findings open the possibility that genes can carry additional,

currently unknown codes, " explains Dr. Uri Alon, principal

investigator on the project. " These findings point at possible

selection forces that may have shaped the universal genetic code. "

The genetic code consists of 61 codons--tri-nucleotide sequences of

DNA--that encode 20 amino acids, the building blocks of proteins. In

addition, three codons signal the cellular machinery to stop protein

synthesis after a full-length protein is built.

While the best-known function of genes is to code for proteins, the

DNA sequences of genes also harbor signals for folding,

organization, regulation, and splicing. These DNA sequences are

typically a bit longer: from four to 150 or more nucleotides in

length.

Alon and his doctoral student Shalev Itzkovitz compared the real

genetic code to alternative, hypothetical genetic codes with

equivalent codon-amino acid assignment characteristics. Remarkably,

Itzkovitz and Alon showed that the real genetic code was superior to

the vast majority of alternative genetic codes in terms of its

ability to encode other information in protein-coding genes--such as

splice sites, mRNA secondary structure, or regulatory signals.

Itzkovitz and Alon also demonstrated that the real genetic code

provides for the quickest incorporation of a stop signal--compared

to most of the alternative genetic codes--in cases where protein

synthesis has gone amiss (situations that scientists

call " frameshift errors " ). This helps the cell to conserve its

energy and resources.

" We think that the ability to carry parallel codes--or information

beyond the amino acid code--may be a side effect of selection for

avoiding aberrant protein synthesis, " says Itzkovitz. " These

parallel codes were probably exploited during evolution to allow

genes to support a wide range of signals to regulate and modify

biological processes in cells. "

The results of this study will be useful for researchers seeking to

identify DNA sequences that regulate the expression and function of

the genome. Many currently known regulatory sequences reside in non-

protein-coding regions, but this may give scientists incentive to

delve deeper into the protein-coding genes in order to solve life's

mysteries.