Summary
Highlights
Codon tables show which amino acids correspond to mRNA or DNA bases. To use a codon table with mRNA bases for a given DNA sequence, first convert the DNA sequence into its complementary mRNA sequence. Then, for each three-base codon, locate the corresponding amino acid in the table by finding the first, second, and third bases. For example, for the DNA sequence TAC GGA CGT, the mRNA sequence is AUG CCU GCA, which codes for methionine, proline, and alanine.
DNA is a long molecule carrying genetic information that must be tightly packed to fit into cells. It wraps around histone proteins to form a DNA-histone complex, which coils further into chromatin, forming chromosomes. A gene is a section of DNA that codes for polypeptides, located at a specific locus on a chromosome. The genome is all genetic material in an organism's cells, coding for the proteome (all proteins). Exons are coding parts of DNA, while introns are non-coding parts.
Eukaryotic cells (plants, animals) have complex cells with a nucleus, while prokaryotic cells (bacteria) are simpler single-celled organisms without a nucleus. Eukaryotic DNA is stored in the nucleus, is long and linear, and is associated with histones and contains introns. Prokaryotic DNA is found in the cytoplasm, is shorter and circular (including plasmids), is not associated with histones, and generally lacks introns. Mitochondrial and chloroplast DNA in eukaryotes resembles prokaryotic DNA, suggesting an ancient relationship.
The genetic code is the sequence of bases in DNA that determines the sequence of amino acids in polypeptides. It is a triplet code, meaning three DNA bases code for one amino acid. These DNA triplets are transcribed into mRNA codons, which then code for specific amino acids. The genetic code is universal, meaning the same triplet codes for the same amino acid in almost all organisms. It is non-overlapping, with each base read only once, and degenerate, as most amino acids are coded for by more than one triplet.