Complementary DNA, coding

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. 

Expressed Sequence Tags and In Silico Methods Expressed sequence tags (ESTs) are short nucleotide sequences of complementary DNA with about 200-500 base pairs. They are parts of the DNA that code for the expression of particular proteins. EST sequencing provides a rapid method to scan for all the protein coding genes and to provide a tag for each gene on the genome. 

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 ... 

DNA codes for its own synthesis at the time of cell division. Thus, DNA acts as the agent of inheritance. As is developed below, DNA is a double-stranded helical molecule—the famous double helix—in which the two strands are complementary. DNA is the repository of information that is expressed in synthesis of the proteins of the cell. Therefore, DNA acts as the determinant of the biochemical personality of the cell. ... 

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,... 

Kevlus. D.J. and L. Hood. Eds. The Code of Codes Scientific and Social Issues in the Human Genome Project. Harvard University Press, Cambridge, MA. 1992. Kitey. T.D. "Patents on Random Complementary DNA Fragments. 1 Science. 915 lAugttHl 14, 1992). 

Transcription Transcription is the process of forming a complementary m-RNA strand from the DNA. This process occurs in the cell nucleus. To begin, an enzyme helps the DNA double helix to break apart and uncoil slightly. This allows RNA nucleotide bases to form complementary hydrogen bonds to the DNA bases. In essence, the m-RNA is reading the DNA code. For example, let s imagine a short section of DNA with the following sequence ... 

If the amino acid sequence of a peptide is known, the possible nucleotide sequences of the mRNA and the complementary DNA may be deduced from the genetic code (Chapter 12). The number of possible DNA sequences is directly related to the extent of degeneracy of the genetic code. Unique sets of DNA oligonucleotides can be chemically synthesized, labeled at the 5 end with 32P, and used as probes to isolate a clone with DNA of specific interest. 

The requirement to exactly define and limit the scope of a patent has implications for patents on biological molecules because it leads to patents which can be easily circumvented. This is illustrated by the following example A polypeptide X is claimed and defined by its complementary DNA (cDNA) sequence. An equivalent according to the above-mentioned US definition and covered by this claim, would be the same polypeptide which is expressed by a modified cDNA, containing different base sequences but coding for identical amino acids. Polypeptide X with an exchange of amino acids would currently not be considered as equivalent since innumerable analogs would be possible... 

Conditions for optimal recoveries of poly(A) containing RNA, with minimal contamination from rRNA, were investigated. The poly(A) fractions isolated were effective as an RNA template for the synthesis of complementary DNA with the RNA-dependent DNA polymerase of avian myeloblastosis virus. Poly(dT)-cellulose has also been used both in the purification of a 14 S messenger RNA for the immunoglobulin light chain from microsomes of MOPC 41 mouse myeloma that appeared to code for a precursor protein [117], and in the purification of RNA-dependent DNA polymerase from RNA tumour virus [118]. An example of the use of oligo(dT)-cellulose is provided by the purification of a viral specific RNA from sarcoma virus-transformed nonproducer cells [119]. 

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