Which Determines Which Dna Strand Is The Template
Template vs Coding Strands
It is often useful to distinguish the ii strands of DNA -- the strand that is copied into mRNA and later on translated has the complementary sequence to the mRNA, while the base sequence of the reverse strand directly corresponds to the codons in the mRNA.
The terms template strand, sense strand, and coding strand are unremarkably used to describe one of the two strands of DNA, all the same the classification is quite confusing because different authors have used these terms to describe both strands -- one school argues that the strand copied into mRNA should be considered the template strand, but the other schoolhouse argues that the opposite strand which reflects the sequence in the mRNA should exist considered the template because the corresponding codons are copied into protein. The first definition is used in the figures below, withal, to avert confusion, when using the words template, sense, or coding, it is essential to explicitly define how you are using the terms. I believe that these terms are best defined as described below.
The term template strand refers to the sequence of Dna that is copied during the synthesis of mRNA.
The opposite strand (that is, the strand with a base sequence straight corresponding to the mRNA sequence) is called the coding strand or the mRNA-like strand because the sequence corresponds to the codons that are translated into poly peptide.
Although RNA polymerase must recognize sequences on the template strand, by convention we depict the DNA sequence and regulatory signals on the "mRNA-like" strand. (This makes information technology simpler to directly determine the sequence of the resulting RNA.) The post-obit cartoon shows this concept for a hypothetical gene.
It may be useful to consider a real factor likewise. The DNA sequence of the phage P22 arc gene and some important regulatory sites is shown beneath. The upper strand of Dna is the "mRNA-like" strand. The lower strand is the strand that is complementary to the mRNA. The -35 region (TTGACA) and -10 region (TATATT) of the promoter sequence and the transcriptional start site (the A ) is indicated on the coding strand. Besides annotation that the Dna sequence of the coding strand corresponding to the RNA codons is shown in assuming (of class, the T is a U in the RNA) -- the first codon is ATG the translational start site (fMet) and the last codon is TAA (Ochre) the translational stop codon.
References:
- Arc DNA sequence from Genbank
- Rex, R., and West. Stansfield. 1985. A dictionary of genetics. Oxford Academy Printing, NY.
Please send comments, suggestions, or questions to smaloy@sciences.sdsu.edu
Last modified July 12, 2002
Which Determines Which Dna Strand Is The Template,
Source: http://www.sci.sdsu.edu/~smaloy/MicrobialGenetics/topics/chroms-genes-prots/temp-strand.html
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