Sueoka has pointed out a correlation between per cent amino acid in protein and per cent CG (cytosine plus guanine) in DNA for bacteria. A correlation also. To manufacture proteins, cells have a very strict procedure that first transcribes DNA into mRNA and then translates the mRNA into amino acids. During transcription, DNA is transcribed into messenger RNA when the the base codes in DNA are copied. mRNA serves as the code for assembling amino.
Sciencing Video Vault Proteins In active genes, genetic information determines which proteins are synthesized and when synthesis is turned on or off. These proteins fold into complicated three-dimensional structures, somewhat like molecular origami. Because each amino acid has specific chemical characteristics, the sequence of amino acids determine the structure and shape of a protein. For example, some amino acids attract water, and others are repelled by it.Classification of amino acids - Chemical processes - MCAT - Khan Academy
Some amino acids can form weak bonds to each other, but others cannot. Proteins that catalyze accelerate chemical reactions, for example, have "pockets," which can bind specific chemicals and make it easier for a particular reaction to occur.
Variations in the DNA code of a gene can change either the structure of a protein or when and where it is produced. If these variations change the protein structure, they could also change its function. For example, a single, specific mutation in hemoglobin -- the oxygen-carrying protein abundant in your red blood cells -- affects oxygen transport and is enough to cause sickle-cell anemia.
Traits Variations in a gene can affect traits in several ways. Search term Section 5. Experiments by Francis Crick, Sydney Brenner, and others established the following features of the genetic code by Three nucleotides encode an amino acid. Proteins are built from a basic set of 20 amino acids, but there are only four bases. Simple calculations show that a minimum of three bases is required to encode at least 20 amino acids.
Genetic experiments showed that an amino acid is in fact encoded by a group of three bases, or codon. The code is nonoverlapping. Genetics experiments again established the code to be nonoverlapping.
The code has no punctuation. This is not the case.
Rather, the sequence of bases is read sequentially from a fixed starting point, without punctuation. The genetic code is degenerate.
Relationship Between DNA Bases Genes, Proteins and Traits | Sciencing
Some amino acids are encoded by more than one codon, inasmuch as there are 64 possible base triplets and only 20 amino acids. In fact, 61 of the 64 possible triplets specify particular amino acids and 3 triplets called stop codons designate the termination of translation. Thus, for most amino acids, there is more than one code word. Because the code is highly degenerate, only tryptophan and methionine are encoded by just one triplet each.
The other 18 amino acids are each encoded by two or more. Indeed, leucine, arginine, and serine are specified by six codons each.
The relationship between DNA bases and amino acids. by Rachel Dorrington on Prezi
The number of codons for a particular amino acid correlates with its frequency of occurrence in proteins. Codons that specify the same amino acid are called synonyms. Note that synonyms are not distributed haphazardly throughout the genetic code depicted in Table 5.
An amino acid specified by two or more synonyms occupies a single box unless it is specified by more than four synonyms. Thus, most synonyms differ only in the last base of the triplet. The structural basis for these equivalences of codons will become evident when we consider the nature of the anticodons of tRNA molecules Section What is the biological significance of the extensive degeneracy of the genetic code? If the code were not degenerate, 20 codons would designate amino acids and 44 would lead to chain termination.
The probability of mutating to chain termination would therefore be much higher with a nondegenerate code.
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Chain-termination mutations usually lead to inactive proteins, whereas substitutions of one amino acid for another are usually rather harmless. Thus, degeneracy minimizes the deleterious effects of mutations.
Degeneracy of the code may also be significant in permitting DNA base composition to vary over a wide range without altering the amino acid sequence of the proteins encoded by the DNA.