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The genetic code is the set of rules used by living cells to translate information encoded within genetic material into proteins. Translation is accomplished by the ribosome, which links proteinogenic amino acids in an order specified by messenger RNA (mRNA), using transfer RNA (tRNA) molecules to carry amino acids and to read the mRNA three nucleotides at a time. The genetic code is highly similar among all organisms and can be expressed in a simple table with 64 entries.
Selenocysteine is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the sulfur.
In molecular biology, a stop codon is a codon that signals the termination of the translation process of the current protein. Most codons in messenger RNA correspond to the addition of an amino acid to a growing polypeptide chain, which may ultimately become a protein; stop codons signal the termination of this process by binding release factors, which cause the ribosomal subunits to disassociate, releasing the amino acid chain.
The central dogma of molecular biology deals with the flow of genetic information within a biological system. It is often stated as "DNA makes RNA, and RNA makes protein", although this is not its original meaning. It was first stated by Francis Crick in 1957, then published in 1958:
The Central Dogma. This states that once "information" has passed into protein it cannot get out again. In more detail, the transfer of information from nucleic acid to nucleic acid, or from nucleic acid to protein may be possible, but transfer from protein to protein, or from protein to nucleic acid is impossible. Information here means the precise determination of sequence, either of bases in the nucleic acid or of amino acid residues in the protein.
In biology, translation is the process in living cells in which proteins are produced using RNA molecules as templates. The generated protein is a sequence of amino acids. This sequence is determined by the sequence of nucleotides in the RNA. The nucleotides are considered three at a time. Each such triple results in addition of one specific amino acid to the protein being generated. The matching from nucleotide triple to amino acid is called the genetic code. The translation is performed by a large complex of functional RNA and proteins called ribosomes. The entire process is called gene expression.
Sydney Brenner was a South African biologist. In 2002, he shared the Nobel Prize in Physiology or Medicine with H. Robert Horvitz and Sir John E. Sulston. Brenner made significant contributions to work on the genetic code, and other areas of molecular biology while working in the Medical Research Council (MRC) Laboratory of Molecular Biology in Cambridge, England. He established the roundworm Caenorhabditis elegans as a model organism for the investigation of developmental biology, and founded the Molecular Sciences Institute in Berkeley, California, United States.
In molecular biology, a reading frame is a way of dividing the sequence of nucleotides in a nucleic acid molecule into a set of consecutive, non-overlapping triplets. Where these triplets equate to amino acids or stop signals during translation, they are called codons.
A frameshift mutation is a genetic mutation caused by indels of a number of nucleotides in a DNA sequence that is not divisible by three. Due to the triplet nature of gene expression by codons, the insertion or deletion can change the reading frame, resulting in a completely different translation from the original. The earlier in the sequence the deletion or insertion occurs, the more altered the protein. A frameshift mutation is not the same as a single-nucleotide polymorphism in which a nucleotide is replaced, rather than inserted or deleted. A frameshift mutation will in general cause the reading of the codons after the mutation to code for different amino acids. The frameshift mutation will also alter the first stop codon encountered in the sequence. The polypeptide being created could be abnormally short or abnormally long, and will most likely not be functional.
The Crick, Brenner et al. experiment (1961) was a scientific experiment performed by Francis Crick, Sydney Brenner, Leslie Barnett and R.J. Watts-Tobin. It was a key experiment in the development of what is now known as molecular biology and led to a publication entitled "The General Nature of the Genetic Code for Proteins" and according to the historian of Science Horace Judson is "regarded...as a classic of intellectual clarity, precision and rigour". This study demonstrated that the genetic code is made up of a series of three base pair codons which code for individual amino acids. The experiment also elucidated the nature of gene expression and frame-shift mutations.
The Nirenberg and Matthaei experiment was a scientific experiment performed in May 1961 by Marshall W. Nirenberg and his post-doctoral fellow, J. Heinrich Matthaei, at the National Institutes of Health (NIH). The experiment deciphered the first of the 64 triplet codons in the genetic code by using nucleic acid homopolymers to translate specific amino acids.
The Nirenberg and Leder experiment was a scientific experiment performed in 1964 by Marshall W. Nirenberg and Philip Leder. The experiment elucidated the triplet nature of the genetic code and allowed the remaining ambiguous codons in the genetic code to be deciphered.
The start codon is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome. The start codon always codes for methionine in eukaryotes and archaea and a N-formylmethionine (fMet) in bacteria, mitochondria and plastids.
The history of molecular biology begins in the 1930s with the convergence of various, previously distinct biological and physical disciplines: biochemistry, genetics, microbiology, virology and physics. With the hope of understanding life at its most fundamental level, numerous physicists and chemists also took an interest in what would become molecular biology.
The adaptor hypothesis is a theoretical scheme in molecular biology to explain how information encoded in the nucleic acid sequences of messenger RNA (mRNA) is used to specify the amino acids that make up proteins during the process of translation. It was formulated by Francis Crick in 1955 in an informal publication of the RNA Tie Club, and later elaborated in 1957 along with the central dogma of molecular biology and the sequence hypothesis. It was formally published as an article "On protein synthesis" in 1958. The name "adaptor hypothesis" was given by Sydney Brenner.
Ribosomal frameshifting, also known as translational frameshifting or translational recoding, is a biological phenomenon that occurs during translation that results in the production of multiple, unique proteins from a single mRNA. The process can be programmed by the nucleotide sequence of the mRNA and is sometimes affected by the secondary, 3-dimensional mRNA structure. It has been described mainly in viruses, retrotransposons and bacterial insertion elements, and also in some cellular genes.
An expanded genetic code is an artificially modified genetic code in which one or more specific codons have been re-allocated to encode an amino acid that is not among the 22 common naturally-encoded proteinogenic amino acids.
The T4 rII system is an experimental system developed in the 1950s by Seymour Benzer for studying the substructure of the gene. The experimental system is based on genetic crosses of different mutant strains of bacteriophage T4, a virus that infects the bacteria Escherichia coli.
The RNA Tie Club was an informal scientific club, meant partly to be humorous, of select scientists who were interested in how proteins were synthesised from genes, specifically the genetic code. It was created by George Gamow upon a suggestion by James Watson in 1954 when the relationship between nucleic acids and amino acids in genetic information was unknown. The club consisted of 20 full members, each representing an amino acid, and four honorary members, representing the four nucleotides. The function of the club members was to think up possible solutions and share with the other members.
RECODE is a database of "programmed" frameshifts, bypassing and codon redefinition used for gene expression.
The history of genetics can be represented on a timeline of events from the earliest work in the 1850s, to the DNA era starting in the 1940s, and the genomics era beginning in the 1970s.
References
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- 1 2 "Archived copy". Archived from the original on 14 August 2007. Retrieved 3 November 2012.
{{cite web}}: CS1 maint: archived copy as title (link) - ↑ "Staff - Genetics - Trinity College Dublin". Archived from the original on 10 October 2012. Retrieved 3 November 2012.
- ↑ Riyasaty S, Atkins JF. External suppression of a frameshift mutant in salmonella. J Mol Biol. 1968 Jun 28;34(3):541–57. PMID 4938557
- ↑ Atkins, John F.; Gesteland, Raymond F.Recoding: Expansion of Decoding Rules Enriches Gene Expression. Springer. ISBN 978-0-387-89381-5
- ↑ "Tiny gene discovered hiding in a major family of plant viruses". www.hpj.com. Archived from the original on 25 January 2013. Retrieved 2 February 2022.
- ↑ John F. Atkins and Ray Gesteland (2002). "The 22nd Amino Acid". Science 296 (5572): 1409–1410. doi:10.1126/science.1073339. PMID 12029118
- ↑ Gesteland, Raymond F.; Cech, Thomas; Atkins, John F. (2006). The RNA world: the nature of modern RNA suggests a prebiotic RNA world. Plainview, N.Y: Cold Spring Harbor Laboratory Press. ISBN 0-87969-739-3.
- ↑ Atkins, John F.; Gesteland, Raymond F.; Cech, Thomas. (2011). RNA Worlds: From Life’s Origins to Diversity in Gene Regulation. Plainview, N.Y: Cold Spring Harbor Laboratory Press. ISBN 978-0-879699-46-8.
- ↑ Reville, William (3 November 2011). "The great mysteries of life are biochemical". Irishtimes.com. Retrieved 9 April 2016.
- ↑ Ledford H. Life-changing experiments: The biological Higgs. Nature 483, 528–530 (29 March 2012) doi:10.1038/483528a
- ↑ "WHAT IS LIFE - DNA and Dublin Schrodinger James Watson, francis Crick, Maurice Wilkinson, Rosalind Franklin, Charles Jencks". Whatislife.ie. Retrieved 9 April 2016.
- ↑ Julie Callanan, Stephen R. Stockdale, Evelien M. Adriaenssens, Jens H. Kuhn, Janis Rumnieks, Mark J. Pallen, Andrey N. Shkoporov, Lorraine A. Draper, R. Paul Ross, Colin Hill (2021). "Leviviricetes: expanding and restructuring the taxonomy of bacteria-infecting single-stranded RNA viruses." MICROBIAL GENOMICS doi:10.1099/mgen.0.000686
