Transcription coding strand

Unlike what happens in DNA replication, where both strands are copied, only one of the two DNA strands is transcribed into mRNA. The strand that contains the gene is often called the coding strand, or primer strand, and the strand that gets transcribed is called the template strand. Because the template strand and the coding strand are complementary, and because the template strand and the transcribed RNA are also complementary, the RNA )no ecule produced during transcription is a copy of the DNA coding strand. The only difference is that the RNA molecule has a U everywhere the DNA coding strand has a T. 

Transcription (DNA), 1108-1109 coding strand in, 1108 primer strand in, 1108 promoter sites in, 1108 template strand in, 1108 Transfer RNA, 1108... 

Figure 35-8. The relationship between the sequences of an RNA transcript and its gene, in which the coding and template strands are shown with their polarities. The RNA transcript with a 5 to 3 polarity is complementary to the template strand with its 3 to 5 polarity. Note that the sequence in the RNA transcript and its polarity is the same as that in the coding strand, except that the U of the transcript replaces theT of the gene.

Figure 37-1. This figure illustrates that genes can be transcribed off both strands of DNA. The arrowheads indicate the direction of transcription (polarity). Note that the template strand is always read in the 3 to 5 direction. The opposite strand is called the coding strand because it is identical (except for T for L) changes) to the mRNA transcript (the primary transcript in eukaryotic cells) that encodes the protein product of the gene.

Figure 37-2. RNA polymerase (RNAP) catalyzes the polymerization of ribonucleotides into an RNA sequence that is complementary to the template strand of the gene. The RNA transcript has the same polarity (5 to 3 ) as the coding strand but contains L) rather than T. E coli RNAP consists of a core complex of two a subunits and two p subunits (P and p ). The holoen-zyme contains the 0 subunit bound to the ajPP core assembly. The co subunit is not shown. The transcription "bubble" is an approximately 20-bp area of melted DNA, and the entire complex covers 30-75 bp, depending on the conformation of RNAP.

The answer is A. Because all nucleic acids are synthesized in the 5 to 3 direction, mRNA and the coding strand of DNA must each be oriented 5 to 3, i.e., in the direction of transcription. This means that the bottom strand in this example is the coding strand. The top strand is the template strand. 

Identify the coding strand of DNA from the direction of transcription,... 

Relationship of RNA transcript to DNA RNA is antiparallel and complementary to DNA template strand RNA is identical (except U substitutes for T) to DNA coding strand ... 

More recently, we have extended this study of strand asymmetries in intron sequences to evolutionarily distant eukaryotes [37]. When appropriately examined, all genomes present transcription-coupled excess of T over A ( TA > 0) in the coding strand. In contrast, GC skew is found positive in... 

The two complementary DNA strands have different roles in transcription. The strand that serves as template for RNA synthesis is called the template strand. The DNA strand complementary to the template, the nontemplate strand, or coding strand, is identical in base sequence to the RNA transcribed from the gene,... 

FIGURE 26-2 Template and nontemplate (coding) DNA strands. The two complementary strands of DNA are defined by their function in transcription. The RNA transcript is synthesized on the template strand and is identical in sequence (with U in place ofT) to the nontemplate strand, or coding strand. 

Promoter sequences. In 1975, Pribnow pointed out46 that a series of six known promoters had a conserved 7-base sequence beginning six nucleotides upstream from the initiation site for transcription. Although this sequence varies somewhat from one promoter to another, it has been found in hundreds of E. coli promoters. This is called the -10 region, the Pribnow sequence, or Pribnow box (the last in recognition of the fact that people like to draw boxes around these special sequences). A typical 6-base consensus Pribnow sequence is 5-TATAAT as written for the coding strand, whose sequence corresponds to that of the rnRNA. Only three of these bases are highly... 

The RNA genomes of single-stranded RNA bacterial viruses, such as Q/3, MS2, R17, and f2, are themselves mRNAs. Bacteriophage Q/3 codes for a polypeptide that combines with three host proteins to form an RNA-depen-dent RNA polymerase (replicase). The three host proteins are ribosomal protein SI and two elongation factors for protein synthesis EF-Tu and EF-Ts (see table 28.5). The Q/3 replicase functions exclusively with the Q/3 RNA plus strand template. It first makes a complementary RNA transcript (minus strand) and ultimately uses the minus strand as... 

Transcription by E. coli RNA polymerase occurs in three phases initiation, elongation and termination. Initiation involves binding of the enzyme to a promoter upstream of the gene. During elongation, the antisense DNA strand is used as the template so that the RNA made has the same base sequence as the sense (coding) strand, except that U replaces T. A termination signal is eventually encountered that halts synthesis and causes release of the completed RNA. 

The sequence of nucleotides within the single-stranded mRNA is assembled according to the complementary-base-pairing (Chap. 7) instructions from one of the strands of duplex DNA, which contains the gene. The DNA strand that bears the same sequence as the mRNA (except for T instead of U) is called the coding strand or sense strand. The other strand of DNA which acts as the template for transcription is called the template or antisense strand. Some textbooks do not define sense" and antisense in the way described here, and for this reason it may be preferable to use coding and template when referring to a particular strand. 

To transcribe a particular stretch of sequence the RNA polymerase binds to the DNA at a site called a promoter, just upstream (i.e., on the 5 side) of the transcriptional start site defined by the template or coding strand. 

SP6 polymerase will read the bottom (template) strand 3 — -5 and produce a transcript in the 5 — -3 direction that is identical to the top (coding) strand, with uracil (U) in place of thymine (T). 

C represents a segment of the template strand of a molecule of DNA. Draw (a) the coding strand (b) the mRNA that is synthesized from C during transcription (c) the tRNA anticodons that are complementary to the mRNA codons (d) the amino acids (use one-letter codes) that form the peptide that C codes for. 

Figure 5.26. Complementarity between mRNA and DNA. The base sequence of mRNA (red) is the complement of that of the DNA template strand (blue). The sequence shown here is from the tryptophan operon, a segment of DNA containing the genes for five enzymes that catalyze the synthesis of tryptophan. The other strand of DNA (black) is called the coding strand because it has the same sequence as the RNA transcript except for thymine (T) in place of uracil (U).

Figure 5.27. Promoter Sites for Transcription. Promoter sites are required for the initiation of transcription in both (A) prokaryotes and (B) eukaryotes. Consensus sequences are shown. The first nucleotide to be transcribed is numbered +1. The adjacent nucleotide on the 5 side is numbered -1. The sequences shown are those of the coding strand of DNA.

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