TY - JOUR. T1 - The number of amino acids in a genetic code. AU - Amikura, Kazuaki. AU - Kiga, Daisuke. PY - 2013/8/21. Y1 - 2013/8/21. N2 - It is generally accepted that the universal genetic code evolved from a simpler form that employed fewer amino acids. We have recently developed a simplified genetic code only using 19 amino acids. Simplified codes will provide not only new insights into primordial genetic codes, but also an essential protein engineering tool for the assessment of the early stages of protein evolution and for the improvement of pharmaceuticals. In this review, we describe the evolution of the number of amino acids in a genetic code. We also discuss the utility of engineered genetic codes having a different number of amino acids from that of the universal code.. AB - It is generally accepted that the universal genetic code evolved from a simpler form that employed fewer amino acids. We have recently developed a simplified genetic code only using 19 amino acids. ...
Of Men and Moths is a popularized account of Bernard Kettlewell s investigations of the phenomenon of industrial melanism, the rapid rise in frequency of dark forms of many moth species downwind of manufacturing centers that occurred as an apparent consequence of large-scale air pollution associated with the industrial revolution. Kettlewell s experiments are widely cited as demonstrating that this change is due to natural selection, and, in particular, the selective advantage of dark coloration against birds in sootdarkened environments. Hooper accuses Kettlewell of committing fraud and members of E.B. Ford s Oxford School of Ecological Genetics of conspiring to hide details of outstanding problems surrounding the phenomenon to advance their own pan-selectionist agenda. The book concludes by reviewing how the career of a lone dissenter, Ted Sargent, was derailed as a result of his heresy. The subtitle is apt, but not for reasons the author intends. The intrigue surrounding this book rests in ...
The evolutionary origin of photosynthetic reaction centers has long remained elusive. Here, we use sequence and structural analysis to demonstrate an evolutionary link between the cytochrome b subunit of the cytochrome bc(1) complex and the core polypeptides of the photosynthetic bacterial reaction center. In particular, we have identified an area of significant sequence similarity between a three contiguous membrane-spanning domain of cytochrome b, which contains binding sites for two hemes, and a three contiguous membrane-spanning domain in the photosynthetic reaction center core subunits, which contains binding sites for cofactors such as (bacterio)chlorophylls, (bacterio)pheophytin and a non-heme iron. Three of the four heme ligands in cytochrome b are found to be conserved with the cofactor ligands in the reaction center polypeptides. Since cytochrome b and reaction center polypeptides both bind tetrapyrroles and quinones for electron transfer, the observed sequence, functional and ...
A sequence of amino acids is the blueprint of life. The Genome Project is a coordinated effort to map the human genetic code.* Our genetic code can be compared to a library; not all of the books are read, or in genetic terms-transcribed. Half of human genes effect CNS functioning. It is therefore estimated that 70,000 genes are expressed within the human brain. Currently, detailed information is available for 1000 to 2000 structural and regulatory genes active within the brain.** Transcription of the genetic code of neurons appears to be the event that determines the constitution of dendritic and synaptic architecture. The secondary messenger system in the cell alters the manner in which the genetic code is read by stimulating and/or inhibiting different functions. With the assistance of the promotor gene, the secondary messenger activates the structural gene, which stimulates the production of regulatory genes that stimulate or inhibit other genes. The process is then repeated, stimulating late ...
Where do physical traits such as height and eye color come from? Biologists say these characteristics are phenotypic (physical) expressions of the genotype-the genetic code. The case for creation can be seen in this amazing genetic code of life. The human bodys trillions of cells use over 75 special kinds of protein and RNA molecules to make one protein following DNAs detailed instructions. A second genetic code has recently been discovered, adding to the complexity of the already intricate molecule of heredity.1. What was the origin of this code? Was it through chance and time (evolution) or design and organization (creation)? The materialistic explanation (evolution) is the antithesis of biblical creation. Could the origin of the genetic code be just a random event? Hardly.2 In fact, a chance origin of biological information is considered by those involved in such research to be inadequate.3 Advocates of evolution must attempt a purely secular explanation of what is quite obviously an ...
A discovery by University of Nebraska-Lincoln researchers expands understanding of the genetic code, and may help revise a tenet of this universal language of life. In cells, the genetic code essentially provides instructions for creating proteins, the basic structural molecules of life. The code includes a series of unique three-letter code words, called codons. These genetic passwords dictate insertion of amino acids, the building blocks of proteins. While codons may change to code for different amino acids in different organisms, a long-held precept of the genetic code is that one codon provides the password only for one amino acid in an organism. Not always, UNL scientists discovered. We showed that one codon may code for two amino acids, even within the same gene. Thats really unexpected, said Vadim Gladyshev, the biochemistry professor whose team made the discovery. Gladyshev; Anton Turanov, a graduate student at the time of this research; Alexey Lobanov, senior research associate; ...
Expanding the Genetic Code using the PylRS/tRNACUA pair. A. An unnatural amino acid (blue star) is taken up by the cell. It is specifically recognized by an orthogonal aminoacyl-tRNA synthetase and attached to the orthogonal amber suppressor tRNACUA (blue trident), which is decoded on the ribosome in response to an amber codon. Natural amino acids are shown as black ovals. B. Orthogonal synthetase tRNACUA pairs are generated in two steps: import of a heterologous tRNACUA into a host containing a set of natural synthetases (grey) that use natural amino acids, and the subsequent selection of a mutated active site in the orthogonal synthetase to recognize the unnatural amino acid. C. A large library of active site variants of the synthetase is subject to positive selection for activity with either natural or unnatural amino acids, by virtue of their ability to suppress a stop codon in a gene essential for survival. Synthetases using natural amino acids are subsequently removed by a negative ...
Scientists for years have known that the genetic code found in all living things contains many layers of complexity. But new research from the University of Rochester cracks the code more deeply, clarifying for example why some genes are inefficiently translated into proteins.. In a study published in the journal Cell, the researchers, co-led by Beth Grayhack, Ph.D., of the UR School of Medicine and Dentistry, discovered the existence and identity of 17 pairs of inefficient codons (DNA nucleotides or bases) within the genetic code.. Scientists have generally considered each piece of the genetic code (or codon) as a single "word" in a language. But the new data suggests some codon combinations act as compound words or phrases whose order and pairing has a significant impact on the translation of genes into proteins.. "Consider the words pancake versus cake pan, " said Grayhack, an associate professor of Biochemistry and Biophysics, Pediatrics, and Cancer, in the Center for RNA Biology, at the ...
To a first approximation, hydrogen bonding between two groups in water is not energetically favorable because roughly equivalent hydrogen bonds to water must be exchanged for one such new bond. Thus, in enthalpic terms, solvation effects will not favor a hydrogen bonded pairing of two nucleobases. The bases G and C must first lose several hydrogen bonds to water in order to form a triply-hydrogen bonded pair. In addition, the bases lose entropy of relative translation and rotation in order to form the complex, a destabilizing effect. However, other entropic effects favor this pairing: The entropy of the freed water molecules is likely to be favorable; moreover, the formation of the second and third H-bond in the base pair comes with little additional translational/rotational entropy penalty. This is also true as multiple pairs are formed between two strands. Thus, the hydrogen bonding in a pair does appear to be energetically favorable in the context of a larger double helix ...
The relationships between the DNA nucleotide bases, quantitatively expressed throughout the Watson-Crick base-pairings, permit the representation of the standard genetic code as a cube inserted in the Euclidean three-dimensional vector space $\mathbb{R}^3$ [3,4]. In particular, it is plausible that the present standard genetic code was derived from an ancestral code architecture with five or more bases (see main text for full discussion). The algebraic and biological model suggests the plausibility of the transition from a primeval code with an extended DNA alphabet $\mathfrak{B}$ ={D,A,C,G,U} to the present standard code, where the symbol "D" represents one or more hypothetical bases with unspecific pairings. It is important to observe that though the evidence from organic chemistry experiments supports the necessity of five or more DNA bases in the primordial genetic system apparatus, the formal development of the algebraic theory necessarily leads to an extension of the DNA base alphabet. In ...
MODEL RELEASED. Genetic code. Conceptual computer artwork of a DNA double helix (yellow) with nucleotide base sequences (letters), a womans face and binary code (zeros and ones). A DNA (deoxyribonucleic acid) helix is composed of two twisting sugar-phosphate molecules linked by pairs of bases. The sequence of base pairs determines the genetic code, the instructions that control and transmit an organisms hereditary traits. There are four types of base: adenine (A), cytosine (C), guanine (G) and thymine (T). Binary code is another method of storing information. - Stock Image G110/0654
One of the first projects for a beginning Python Bioinformatics coder is to construct a dictionary holding the genetic code and use it to translate genes. The other day I posted code for a module defining a class that constructs a Python dictionary holding the Genetic Code using list comprehension. The same class makes a "reverse" codon dictionary where the keys are amino acids and the values are lists of synonomous codons. It also makes a third dictionary where the keys are codons and the values are lists of synonomous codons, but without the codon that is the key ...
Biology is a science with an exception to just about every rule. But very nearly all organisms use a genetic code. A genetic code, encoded into DNA usually runs every aspect of an organisms ...
If you are looking for information on cracking the genetic code and genetics history, read on to learn more about how genetic code was deciphered, who was responsible, and what place it has in todays society and medical community.
The genetic code has the remarkable property of error minimization, whereby the arrangement of amino acids to codons is highly efficient at reducing the deleterious effects of random point mutations and transcriptional and translational errors. Whether this property has been explicitly selected for is unclear. Here, three scenarios of genetic code evolution are examined, and their effects on error minimization assessed. First, a simple model of random stepwise addition of physicochemically similar amino acids to the code is demonstrated to result in substantial error minimization. Second, a model of random addition of physicochemically similar amino acids in a codon expansion scheme derived from the Ambiguity Reduction Model results in improved error minimization over the first model. Finally, a recently introduced 213 Model of genetic code evolution is examined by the random addition of physicochemically similar amino acids to a primordial core of four amino acids. Under certain conditions, 22% ...
The genetic code has the remarkable property of error minimization, whereby the arrangement of amino acids to codons is highly efficient at reducing the deleterious effects of random point mutations and transcriptional and translational errors. Whether this property has been explicitly selected for is unclear. Here, three scenarios of genetic code evolution are examined, and their effects on error minimization assessed. First, a simple model of random stepwise addition of physicochemically similar amino acids to the code is demonstrated to result in substantial error minimization. Second, a model of random addition of physicochemically similar amino acids in a codon expansion scheme derived from the Ambiguity Reduction Model results in improved error minimization over the first model. Finally, a recently introduced 213 Model of genetic code evolution is examined by the random addition of physicochemically similar amino acids to a primordial core of four amino acids. Under certain conditions, 22% ...
The Wobble Hypothesis, by Francis Crick, states that the 3rd base in an mRNA codon can undergo non-Watson-Crick base pairing with the 1st base of a tRNA anticodon [1] The mRNA codons first 2 bases form Hydrogen bonds with their corresponding bases on the tRNA anticodon in the usual Watson-Crick manner, in that they only form base pairs with complimentary bases. [2] However, the formation of Hydrogen bonds between the 3rd base on the codon and the 1st base on the anticodon can potentially occur in a non-Watson-Crick manner. Therefore different base pairs to those usually seen can form at this position. [3] ...
The discovery of a universal genetic code utilized by all existing organisms became the backbone of biology. The coding capacity underwent changes during evolution, but its main fluctuation results from its different reading and regulation. The genetic code thus represents a sort of receptacle of living organism evolution. In this article, we propose an analogy between the genetic code and a broader Platonic hypodoché, a concept that Alfred North Whitehead used to explain various aspects of science.
A linear chain of amino acid residues is termed a polypeptide. A protein includes at least a person prolonged polypeptide. Limited polypeptides, that contains less than twenty-thirty residues, are hardly ever considered to be proteins and are generally termed peptides, or often oligopeptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid residues inside of a protein is described with the sequence of the gene, thats encoded inside the genetic code. Generally, the genetic code specifies twenty standard amino acids; however, in selected organisms the genetic code can incorporate selenocysteine and-in specific archaea-pyrrolysine ...
I think tblastn uses genetic codes from the gc.prt file so you could presumably add your custom code there and pass its index to option db_gen_code. You may have to recompile the program though (gc.prt is in the src/c++/objects/seqfeat directory of the source code).. ...
A "hidden" code linked to the DNA of plants allows them to develop and pass down new biological traits more rapidly than previously thought, according to research by scientists at the Salk Institute for Biological Studies and The Scripps Research Institute. The study, published recently in the journal Science, provides the first evidence that an organisms "epigenetic" code-an extra layer of biochemical instructions in DNA-can evolve more quickly than the genetic code and can strongly influence biological traits. While the study was limited to a commonly studied single plant species called Arabidopsis thaliana, the findings hint that the traits of other organisms, including humans, might also be dramatically influenced by biological mechanisms that scientists are just beginning to understand. "I have been a genetics researcher for 25 years and rarely have I seen, let alone participated in, a game changing study," said Nicholas Schork, a professor of Molecular and Experimental Medicine at ...
View Notes - Translation from BIO 101 at Texas State. Translation The genetic code is transferred to an amino acid sequence in a protein through the translation process, which begins with the arrival
Human mitochondria contain their own genome, which uses an unconventional genetic code. In addition to the standard AUG methionine codon, the single mitochondrial tRNA Methionine (mt‐tRNAMet) also recognises AUA during translation initiation and elongation. Post‐transcriptional modifications of tRNAs are important for structure, stability, correct folding and aminoacylation as well as decoding. The unique 5‐formylcytosine (f5C) modification of position 34 in mt‐tRNAMet has been long postulated to be crucial for decoding of unconventional methionine codons and efficient mitochondrial translation. However, the enzymes responsible for the formation of mitochondrial f5C have been identified only recently. The first step of the f5C pathway consists of methylation of cytosine by NSUN3. This is followed by further oxidation by ABH1. Here, we review the role of f5C, the latest breakthroughs in our understanding of the biogenesis of this unique mitochondrial tRNA modification and its involvement in
There are currently three major theories on the origin and evolution of the genetic code: the stereochemical theory, the coevolution theory, and the error-minimization theory. The first two assume tha
Researchers at the Scripps Research Institute in La Jolla, California, introduced DNA molecules not found in nature to a common bacterium The E. coli bugs are able to grow and reproduce as normal despite containing two extra letters in their genetic code Research involved overcoming a billion years of evolution to get the expanded…
1.What is the genetic code? (1 point) The order of amino acids in proteins makes up the genetic code. The order of amino acids in mRNA makes up the genetic code. The order of nitrogen bases in tRNA makes up the genetic code. The order ...
Posted on 10/13/2011 3:44:55 AM PDT by Just4Him. The genetic code of the germ that caused the Black Death has been reconstructed by scientists for the first time. The researchers extracted DNA fragments of the ancient bacterium from the teeth of medieval corpses found in London. They say the pathogen is the ancestor of all modern plagues. The research, published in the journal Nature, suggests the 14th Century outbreak was also the first plague pandemic in history ...
The genetic code has been regarded as arbitrary in the sense that the codon-amino acid assignments could be different than they actually are. This general idea has been spelled out differently ...
Dangerously Thin: A Case Study on the Genetic Code 1. Through genetic testing Henry was discovered that that both of his CYP2C9 genes contain a mutation. The...
See Blood Types, Body Types and You: Why Your Unique Genetic Code Is the Key to Losing Weight for Life by Joseph Christiano in our Christian Book store for $11.69 (Save 35%) - Overview A world-renowned health and fitness coach updates his proven weight-loss program and explains how a well-balanced eatin
Artificial genetic code, for the first time replicated in a living organism, opens the door to new biological customizations for vaccines and antibiotics.
Press Release issued Mar 20, 2014: Cazeje International LLC today announced that their new health supplement, Genetic Code, has been released and is ready for shipping as of late February and early March 2014.
Benners solution was to tag the HIV or HBV with nucleic acids in a modified branched‐DNA assay by using the expanded genetic code, which could be more easily separated from the patients DNA and RNA. "Here, we would tag the HIV or hepatitis virus with a sequence today built not from GACT, the standard bases, but rather from GACTSBPZ, a sequence that contains some of our extra bases," Benner explained. "A virus particle, one of 10 in a millilitre, having a tag DNA with the sequence GACTSBPZ, would bind to a complementary sequence attached to a spot on the glass slide having the sequence CTGABSZP, since in our expanded DNA alphabet, Z binds to P and B binds to S.". XNA‐based therapeutic applications could also circumvent the crucial problem of delivery that plagues RNA‐based therapies. In particular, short interfering RNA holds great therapeutic potential as it can interfere with gene expression and block undesirable pathways implicated in disease. But to reach targets inside a cell, RNA ...
whats interesting is that the tRNA also comes from the genetic code. even more interesting are suppressor mutations, where if a single base is changed in a gene (for instance, causing the placement of stop codon instead of an amino acid, which would be disasterous for the cell) the corresponding sequence that encodes for the tRNA of that original amino acid can also undergo a mutation that changes the anticodon part of the tRNA to set things back again! thus unnatural tRNAs that violate the universality of the genetic code can exist as a survival mechanism ...
Generally, if /transl_table qualifier is appropriately described with a number of the genetic code, the nucleotide sequence is automatically translated to amino acid sequence according to the genetic code. In exceptional cases of specific codons (selenocysteine etc.) that is not followed the genetic codes, describe /transl_except qualifier, appropriately. In cases of RNA editing,ribosomal frameshift,mitochondrial TAA stop codon, see Example of submission and describe with /exception and /translation, /ribosomal_slippage, /transl_except, respectively. In case of rare initiation of translation, staring with an amino acid other than methionine, describe the location of CDS feature with starting from ,, operatively indicating 5end not complete. And describe brief explanation about the translation mechanism in /note qualifier. ...
Research topics: Functional genomics and biology of tRNA, RNA epigenetics. Translational regulation is related to the dynamic properties of tRNA that constantly change to facilitate stress response and adaptation to new environments and to control gene expression. We developed microarray and high-throughput sequencing methods that measure tRNA abundance, fraction of aminoacylation, misacylation and modification dynamics at the transcriptomic scale. We are exploring roles of tRNA in translational control in mammalian cells.. A central tenet of biology is the accurate flow of information from nucleic acids to proteins through the genetic code. It is commonly believed that translation deviating from the genetic code is avoided at all times. We discovered that mammalian cells can deliberately reprogram the genetic code through tRNA misacylation upon innate immune activation and chemically triggered oxidative stress. We are investigating how regulated mis-translation is used as a mechanism for stress ...
The genes within the genome (genetic code) of cattle need to be identified and defined before variability of these genes among cattle (individuals and breeds) can be identified. One goal is to determine whether such variations when found are associated with enhanced or decreased resistance to infectious diseases. The cattle genome has been largely sequenced (that is, the genetic code read), and now one of the purposes of the international community effort is to annotate the bovine genome (define genes within the genetic code).
Instructions: Paste in or upload DNA sequences and hit "Submit query". The RevTrans server will then virtually translate the first 75 sequences and align the resulting peptide sequences using Dialign2 with default settings. Finally RevTrans constructs a multiple DNA alignment using the peptide alignment as a scaffold. The translation process is by default done using the Standard Genetic Code (alternative translation tables can be selected) and has support for the full IUPAC alphabet of degenerate nucleotides. If you want more control over the alignment process RevTrans also accepts user provided peptide alignments. This will give you the opportunity to use your preferred alignment software and to optimize the parameters. If you need to translate your DNA sequences prior to alignment this can be done by using the "Translate only" button above. When providing your own peptide alignment, RevTrans will accept arbitrarily large input files. Please read the CBS access policies for information about ...
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Welded low carbon steel gas cylinder exceeding 5 litre water capacity for low pressure liquefiable gases:Pt 2 Cylinders for liquefiable gases other than ...
Mice with fluorescent green cells. Mammal cells usually contain two sets of chromosomes - one set inherited from the mother and one from the father. The genetic information contained in these chromosome sets helps determine how our bodies develop. Changes in this genetic code can lead to or increase the risk of developing disease.. To understand how our genes function, scientists manipulate the genes in animal models - such as the fruit fly, zebrafish and mice - and observe the effects of these changes. However, as each cell contains two copies of each chromosome, determining the link between a genetic change and its physical effect - or phenotype - is immensely complex.. Now, in research published today in the journal Nature, Drs Anton Wutz and Martin Leeb from the Wellcome Trust Centre for Stem Cell Research at the University of Cambridge report a technique that enables them to create stem cells containing just a single set of chromosomes from an unfertilised mouse egg cell. The stem cells ...
All life on Earth, for instance, relies on DNA (Figure 3) and RNA for replication, the issuing of instructions at the molecular level, and heredity. Does that mean that our Earthly DNA is universal throughout the cosmos? Thats actually hard to believe, since studies show that even our DNA could continue to function after the insertion of laboratory-created bases into its molecular structure. Similarly, different genetic codes can be used to create amino acids, which are the building blocks of proteins. Furthermore, one of the pillars of Darwins theory of evolution by means of natural selection is the concept of a common ancestor-in his words, "all the organic beings which have ever lived on Earth have descended from some one primordial form." This means that the fact that all life forms on Earth use the same DNA is not that surprising, and it certainly does not necessarily imply that this is the only way for life to evolve. The biochemistry involved in the emergence of life may not be unique ...
Heterochromatin - chromatin organisation, lines the nuclear membrane at the pores. Euchromatin - threadlike, delicate, abundant in active transcribed cells, regions of DNA to be transcribed or duplicated, must be coiled before genetic code can be read.. All the human bodys nucleated cells contain 46 chromosomes (23 pairs). Contain all the information that governs all cellular activitys. DNA molecules - form of genes. DNA molecule regulate specific functions. blueprint determines synthesis of an RNA molecule or polypeptide. Not visible in non dividing cells. ...
The student biologist will be able to (6A) identify components of DNA and describe how information for specifying the traits of an organism is carried in the DNA (6) Science concepts. The student knows the mechanisms of genetics, including the role of nucleic acids and the principles of Mendelian Genetics. The student is expected to: A. identify components of DNA, and describe how information for specifying the traits of an organism is carried in the DNA; B. recognize that components that make up the genetic code are common to all organisms; C. explain the purpose and process of transcription and translation using models of DNA and RNA; D. recognize that gene expression is a regulated process; and H. describe how techniques such as DNA fingerprinting, genetic modifications, and chromosomal analysis are used to study the genomes of organisms.
Cell division is controlled by genes that are located in the cell nucleus. They function like an instruction manual telling the cell what proteins to make, how it will divide and how long it will live for. This genetic code can get damaged by a number of factors resulting in errors occurring within the instruction manual. These errors can dramatically alter how the cell functions. Instead of resting the cell may continue dividing, instead of dying the cell may stay alive ...
Conductivity experiments with DNA have already been performed. With this in mind, we experimented using the charge transport of DNA to receive signals about detection of similar DNA sequences of another species through the linking of complementary ssDNA on chips; subsequently, these methods can be used to prove whether certain genetic codes are present in a given specimen of DNA.
One of the rapidly expanding and exciting research fields in molecular biology is the area of epigenetics. In the study of epigenetic modifications, scientists analyze DNA that has been modified in such a way that its chemistry is changed, but not the actual base pairs that make up the genetic code of the sequence. Its like a separate control code and system imposed upon and within the standard code of DNA sequence.. Because epigenetic modifications in the genome are related to gene expression, researchers have been using highly advanced technologies for comparing these differences in humans and chimps for regions of the genome that they both have in common. More... More... ...
An international team led by University of Toronto scientists Timothy Hughes and Quaid Morris has unraveled most of a code that controls how DNA becomes the proteins that make up cells, a process called gene expression and, in the process, uncovered a possible ca
It has been repeatedly proposed to expand the scope for SETI, and one of the suggested alternatives to radio is the biological media. Genomic DNA is already used on Earth to store non-biological information. Though smaller in capacity, but stronger in noise immunity is the genetic code. The code is a flexible mapping between codons and amino acids, and this flexibility allows modifying the code artificially. But once fixed, the code might stay unchanged over cosmological timescales; in fact, it is the most durable construct known. Therefore it represents an exceptionally reliable storage for an intelligent signature, if that conforms to biological and thermodynamic requirements. As the actual scenario for the origin of terrestrial life is far from being settled, the proposal that it might have been seeded intentionally cannot be ruled out. A statistically strong intelligent-like "signal" in the genetic code is then a testable consequence of such scenario. Here we show that the terrestrial code ...
Schultz and his colleagues succeeded in making the 22-amino acid E. coli by exploiting the redundancy of the genetic code. When a protein is expressed, an enzyme reads the DNA bases of a gene (A, G, C, and T), and transcribes them into RNA (A, G, C, and U). This so-called "messenger RNA" is then translated by another protein-RNA complex, called the ribosome, into a protein. The ribosome requires the help of transfer RNA molecules (tRNA) that have been "loaded" with an amino acid, and that requires the help of a "loading" enzyme. Each tRNA recognizes one specific three-base combination, or "codon," on the mRNA and gets loaded with only the one amino acid that is specific for that codon. During protein synthesis, the tRNA specific for the next codon on the mRNA comes in loaded with the right amino acid, and the ribosome grabs the amino acid and attaches it to the growing protein chain. The redundancy of the genetic code comes from the fact that there are more codons than there are amino acids ...