Nucleotide sequences encoding mRNA

Retrieve nucleotide sequence encoding mRNA of human (Homo sapiens) soluble aldehdyde dehdrogenase 1 (ALDH1 gil 1429705) and perform gene identification with GeneFinder. 

Retrive nucleotide sequence encoding mRNA of human mitochondrial aldehyde dehydrogenase 2 (ALDH 2 gil 1436532) and carry out gene identification with GeneMark. 

Figure 10.3. Identification of open reading frames with ORF Finder. The nucleotide sequence encoding human proopiomelanocortin mRNA (1071 bp) is submitted to ORF Finder. The return shows frame bars (from Frame +1 to Frame -3) with highlighted relative length of ORF and the list of ORF arranged according to their lengths.

More than 250 amino acids have been isolated from living systems, but only 20 appear to be encoded by the triplet nucleotide sequence in mRNA. Posttranslation modification accounts for the panoply of amino acids found in contemporary proteins. Hence, the limited number of amino acids encoded by the genome must be a consequence of evolutionary selection. Rohlfing and Saunders (1978) have proposed that it is the specific tripartite interaction among activating enzymes, tRNAs, and amino acid which explains why the amino acid code is limited to the 20 commonly found amino acids. 

THE NUCLEOTIDE SEQUENCE OF AN mRNA MOLECULE CONSISTS OF A SERIES OF CODONS THAT SPECIFY THE AMINO ACID SEQUENCE OF THE ENCODED PROTEIN... 

Finally, RNA editing can be involved, as in the case of the amphibian bombesin-like peptides, where nucleotides in the mRNA are changed and the final protein is not a direct reflection of the sequence encoded in the gene. RNA editing is also seen in the glutamate (Ch. 15) and serotonin receptors (Ch. 13 and Ch. 15) and probably will be found elsewhere as detection methods become more sophisticated. 

Translation of the information encoded in DNA, expressed as a particular nucleotide sequence, into a protein, expressed as an amino acid sequence, depends on the genetic code. In this code, sequences of three nucleotides (termed a codon) represent one of the 20 amino acids that compose the protein molecule. Because there are 64 codons which can be constructed for the four different bases, and only 20 different amino acids that are coded for, several amino acids may be coded for by more than one codon. There are also three codons, called stop codons, that terminate the transfer of information. Furthermore, although all cells contain the same complement of genes, certain cells (for example, the neurons) have specialized genes that encode specific proteins for the synthesis of specific transmitters. The expression of such genes is under the control of regulatory proteins called transcription factors which control the transcription of mRNAs from the genes they control. 

D. tRNAs are small molecules that function as adaptors to convert or translate the nucleotide sequence information of mRNAs into the amino acid sequences of the proteins they encode. 

Trans splicing. Every mRNA in trypanosomes has, at its 5 end, a short 35-nucleotide sequence that is not encoded in the transcribed gene. It was found that for each mRNA molecule two transcripts are formed and are spliced together, always with the 5 piece from a short SL (spliced leader) gene being joined to each of the others.639 This trans splicing has since been observed in many plants, animals, and protists.640... 

Table 6.1 shows the relationship between the codon sequence in mRNA and its corresponding amino acid in the new protein. Because there are 64 (43) different anticodon combinations and only 20 encoded amino acids, some different anticodon sequences encode for the same amino acid. Generally, all the anticodons matching a given amino acid will have the same first two nucleotides. Exceptions are arginine, serine, and isoleucine. For example, the codon for proline will always start with CC, but the arginine codon may start with either AG or CG. The 3 end of the tRNA anticodon pairs with the 5 end of the mRNA codon. In other words, the codon and anticodon align and bind in an antiparallel fashion. 

The genetic code During translation, the sequence of an mRNA molecule is read from its 5 end is a triplet code by ribosomes which then synthesize an appropriate polypeptide. Both in prokaryotes and eukaryotes, the DNA sequence of a single gene is colinear with the amino acid sequence of the polypeptide it encodes. In other words, the nucleotide sequence of the coding DNA strand, 5 to 3, specifies in exactly the same order the amino acid sequence of the encoded polypeptide, N-terminal... 

Transcript Number of cDNA clones used to reconstruct Complete mRNA sequence known mRNA size (nucleotide number) cDNA clones fully supporting exonic structure Number of exons encoded Protein coding likely Predicted number of AA encoded CCD encoded DD encoded Normal brain expression (specific areas)... 

Rice, G. M., and Strauss, J. H. (1981). Nucleotide sequence of the 26S mRNA of Sindbis virus and deduced sequence of the encoded virus structural proteins. Proc. Natl Acad. Sci. USA 78, 2062-2066. 

Figure 31.34. Leader Region of JKPmRNA. (A) The nucleotide sequence of the 5 end of t p mRNA includes a short open reading frame that encodes a peptide comprising 14 amino acids the leader encodes two tryptophan residues and has an untranslated attenuator region (blue and red nucleotides). (B and C) The attenuator region can adopt two distinct stem-loop structures.

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