Amino acids nucleotides compared

Tissue culture, more frequently used as cell culture, enables animal and plant cells to be cultured in large numbers by techniques comparable to those used in microbiology but, because of the fragile nature of the cells, does require special cultural conditions. The culture media used must supply all the essential factors for growth, such as a wide range of amino acids, nucleotides, enzyme co-factors as well as indeterminate factors that can only be supplied in special products, e.g. foetal bovine serum. The environmental conditions must be carefully controlled, particularly pH, and this is frequently maintained by culturing in a bicarbonate buffer system and a carbon dioxide saturated atmosphere. 

Reflect and Apply What might you infer (or know) about the stability of amino acids, when compared with that of other building-block units of biopolymers (sugars, nucleotides, fatty acids, etc.) ... 

Coxsackie virus strain B3, when introduced into Se-deficient mice, produces a myocarditis that is similar to that of human Keshan s disease, and this virus consistently undergoes mutation at six distinct amino acid (= nucleotide) sites in the Se-deficient but not the control animals. These mutated viruses are then able to produce myocarditis even in selenium-replete control mice. Thus, the virulence change has become permanent by mutation, and the increased virulence is no longer dependent on a simultaneous lack of selenium. Comparable selenium Hmitation-induced mutations in influenza virus have also been shown in Se-deficient mice. It is suggested that in the presence of a low selenium supply, a normally quiescent virus may become activated by increased oxidative stress and host cell apoptosis, the mutation to increased virulence being a survival strategy by the virus. 

The functions of a large proportion of the proteins encoded by the human genome are presently unknown. Recent advances in bioinformatics permit researchers to compare amino acid sequences to discover clues to potential properties, physiologic roles, and mechanisms of action of proteins. Algorithms exploit the tendency of nature to employ variations of a structural theme to perform similar functions in several proteins (eg, the Rossmarm nucleotide binding fold to bind NAD(P)H,... 

Gotoh O. Substrate recognition sites in cytochrome P450 family 2 (CYP2) proteins inferred from comparative analyses of amino acid and coding nucleotide sequences. J Biol Chem 1992 267(1) 83-90. 

The mutation rate fx of the nucleotide (or amino acid) at a sequence site is related to the popular notion of a molecular clock (Zuckerkandl and Pauling, 1965), because it determines after which time the clock ticks and anew mutation arises because of a copying error during meiosis. Whether this clock ticks uniformly is a topic of prolonged debate (summarized in Li, 1997). The question is usually treated by comparing sequence difference at (supposedly) neutral sites with evolutionary distance between species. 

Use the BLAST tool to compare the amino acid sequences for human a-lactalbumin and lysozyme. Repeat the process using BLAST to compare the nucleotide sequences for the genes coding for human a-lactalbumin and lysozyme. 

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