messenger RNAgenetics

Messenger RNA (mRNA) delivers the information encoded in one or more genes from the DNA to the ribosome, a specialized structure, or organelle, where that information is decoded into a protein. In prokaryotes, mRNAs contain an exact transcribed copy of the original DNA sequence with a terminal 5′-triphosphate group and a 3′-hydroxyl residue. In eukaryotes the mRNA molecules are more...

There are three main types of RNA: messenger RNA (mRNA), transfer RNA, and ribosomal RNA (rRNA). In protein formation, mRNA carries codes from the DNA in the nucleus to the sites of protein synthesis in the cytoplasm (the ribosomes). Ribosomes are composed of rRNA and protein; they can “read” the code carried by the mRNA. A sequence of three nitrogenous bases in mRNA specifies...

Ribosomes are the sites at which information carried in the genetic code is converted into protein molecules. Ribosomal molecules of messenger RNA (mRNA) determine the order of transfer RNA (tRNA) molecules that are bound to triplets of amino acids (codons). The order of tRNA molecules ultimately determines the amino acid sequence of a protein because molecules of tRNA catalyze the formation of...

...information in DNA. DNA contains within its structure the blueprint both for its own exact duplication and for the synthesis of a number of types of RNA, among which is a class termed messenger RNA (mRNA). A complementary relationship exists between the sequence of purines (i.e., adenine and guanosine) and pyrimidines (cytosine and thymine) in the DNA comprising a gene and the sequence in mRNA...

The RNA molecules in cells have two main roles. Some, the ribozymes, fold up in ways that allow them to serve as catalysts for specific chemical reactions. Others serve as “messenger RNA,” which provides templates specifying the synthesis of proteins. Ribosomes, tiny protein-synthesizing machines located in the cytoplasm, “read” the messenger RNA molecules and...

...codes for the construction of a specific protein out of a chain of amino acids. Information in DNA is not decoded directly into proteins, however. First it is transcribed, or copied, into a range of messenger ribonucleic acid (mRNA) molecules, each of which encodes the information for one protein (or more than one protein in bacteria). The mRNA molecules are then transported through the nuclear...

Another type of library is a cDNA library. Creation of a cDNA library begins with messenger ribonucleic acid (mRNA) instead of DNA. Messenger RNA carries encoded information from DNA to ribosomes for translation into protein. To create a cDNA library, these mRNA molecules are treated with the enzyme reverse transcriptase, which is used to make a DNA copy of an mRNA. The resulting DNA molecules...

...chickenpox, retinitis, and infectious mononucleosis. After the viral particle attaches to the cell membrane and uncoats, the viral DNA is transferred to the nucleus and transcribed into viral mRNA for the viral proteins. Drugs that are effective against herpesviruses interfere with DNA replication. The nucleoside analogs (acyclovir and ganciclovir) actually mimic the normal nucleoside and...

...each segment of three nucleotides—called a triplet or codon—codes for one particular amino acid in the protein. The nucleotide sequence in the DNA is first transcribed into a molecule of messenger RNA (ribonucleic acid). The RNA, using a slightly different code (represented by the letters A, C, G, and U, the last letter representing the nucleotide base uracil), bears the message that...

Transcription of protein-coding genes results in a type of RNA called messenger RNA (mRNA), so named because it carries a genetic message from the gene on a nuclear chromosome into the cytoplasm, where it is acted upon by the protein-synthesizing apparatus. The transcription machinery contains many items in addition to the RNA polymerase. The successful binding of the RNA polymerase to the DNA...

...Using this code, the DNA synthesizes one strand of ribonucleic acid (RNA), a substance that is so similar structurally to DNA that it is also formed by template replication of DNA. RNA serves as a messenger for carrying the genetic code to those places in the cell where proteins are manufactured. The way in which the messenger RNA is translated into specific proteins is a remarkable and...

...Genes contain unique sequences of DNA that code for specific protein hormones or for enzymes that direct the synthesis of other hormones. The transcription of genes results in the formation of messenger ribonucleic acid (mRNA) molecules.

...subunits. The gene for the large subunits is located in the chloroplast chromosome, while the gene for the small subunits is in the nucleus. Transcription of the DNA of the nuclear gene yields messenger RNA (mRNA) that encodes the information for the synthesis of the small polypeptides. During this synthesis, which occurs on the cytoplasmic ribosomes, some extra amino acid residues are...

...synthesis, and hence development, through an early embryonic stage called the blastula. Most immediate post-fertilization protein synthesis is directed by molecules of ribonucleic acid, known as messenger RNA, that were formed during oogenesis and stored in the egg. In addition, protein synthesis up to the blastula stage (up to a much earlier stage in the mammalian embryo) is directed by the...

...the host cell for almost all of their life-sustaining functions. Unlike true organisms, viruses cannot synthesize proteins, because they lack ribosomes (cell organelles) for the translation of viral messenger RNA (mRNA; a complementary copy of the nucleic acid of the nucleus that associates with ribosomes and directs protein synthesis) into proteins. Viruses must use the ribosomes of their host...

...follows the uncoating of the genome varies for different virus classes. For many virus families the third step in the cycle of infection is transcription of the genome of the virus to produce viral mRNA, followed by the fourth step, translation of viral mRNA into proteins. For those viruses in which the genomic nucleic acid is an RNA that can serve as a messenger (i.e., positive-strand RNA...

Jacob and Monod also proposed the existence of an RNA messenger, a partial copy of the gene substance deoxyribonucleic acid (DNA), that carries genetic information to other parts of the cell. They also found that in a normal cell the balance between regulator and structural genes enables the cell to adapt to varying conditions. An interruption in this balance, however, can stimulate the...

In 1961 Jacob and Monod proposed the existence of a messenger ribonucleic acid (mRNA), a substance whose base sequence is complementary to that of deoxyribonucleic acid (DNA) in the cell. They postulated that the messenger carries the “information” encoded in the base sequence to ribosomes, the sites of protein synthesis; here the base sequence of the messenger RNA is translated...

In 1977 Sharp and his team discovered that the messenger RNA (mRNA) of an adenovirus corresponded to four separate, discontinuous segments of DNA. They found that the segments of DNA that coded for proteins, now called exons, were separated by long stretches of DNA, now called introns, that did not contain genetic information. At the same...

Watson subsequently taught at Harvard University (1955–76), where he served as professor of biology (1961–76). He conducted research on the role of nucleic acids in the synthesis of proteins. In 1965 he published Molecular Biology of the Gene, one of the most extensively used modern biology texts. He later wrote The Double Helix...