B2 Code Research Articles

Assembly of the mitochondrial membrane system. DNA sequence and organization of the cytochrome b gene in Saccharomyces cerevisiae D273-10B.

The mitochondrial genomes of cytoplasmic "petite" (rho-) mutants of Saccharomyces cerevisiae have been used to sequence the cytochrome b gene. A continuous sequence of 6.2 kilobase pairs has been obtained from 71.4 to 80.2 units of the wild type map. This region contains all the cytochrome b mutations previously assigned to the cob1 and cob2 genetic loci. Analysis of the DNA sequence has revealed that in the strain D273-10B, the cytochrome b gene is composed of three exons. The longest exon (b1) codes for the first 252 to 253 amino acids from the NH2-terminal end of the protein. The next two exons (b2 and b3) code for 16 to 18 and 115 to 116 amino acids, respectively. The complete cytochrome b polypeptide chain consists of 385 amino acids. Based on the amino acid composition, the yeast protein has a molecular weight of 44,000. The three exon regions of the cytochrome b gene are separated by two introns. The intron between b1 and b2 is 1414 nucleotides long and contains a reading frame that is continuous with the reading frame of exon b1. This intron sequence is potentially capable of coding for another protein of 384 amino acid residues. The second intron is 733 nucleotides long. This sequence is rich in A + T and includes a G + C cluster that may be involved in processing of the cytochrome b messenger. The organization of the cytochrome b region in S. cerevisiae D273-10B is somewhat less complex than has been reported for other yeast strains i which exon b1 appears to be further fragmented into three smaller exons.

A new class of recurrent codes

Recurrent codes for burst-error correction are defined to be a type B1 code. A type B1 code is capable of correcting all the single burst errors of length <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</tex> or less. A type B2 code is a subclass of a type B1 code with the restriction that the single burst error of length <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</tex> or less occurs within <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</tex> consecutive blocks (it is assumed that <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</tex> is divisible by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l = rb</tex> ). In this paper, the author will present a class of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</tex> -nary recurrent codes--both type B1 and B2 codes--for burst-error correction. The construction procedures for this class of codes are simple and systematic. An interesting relation exists between a type B1 and a type B2 code. If a code is type B2 (with block length <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</tex> , burst-error-correction capability <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l = rb</tex> ), then by reducing the block length by one symbol, the type B2 code becomes a type B1 code, while the burst-error-correction capability remains the same. Both types of codes can be used for the correction of binary burst errors. The correction of binary burst errors will be briefly discussed in this paper.