INTERPOL HANDBOOK ON DNA DATA EXCHANGE AND PRACTICE
INTERPOL HANDBOOK ON DNA DATA EXCHANGE AND PRACTICE
INTERPOL HANDBOOK ON DNA DATA EXCHANGE AND PRACTICE
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APPENDIX 3what is forensic dna profiling?basic dna principles - the structure of dnaNuclear <strong>DNA</strong> molecules are made up of two strands that wrap around each otherin a helix to resemble a twisted ladder. The rungs of the ladder are made up of pairsof smaller molecules (monomers) called bases. There are four different bases presentin <strong>DNA</strong>: adenine (A), cytosine (C), guanine (G), and thymine (T). Each base only bindswith a specific complementary base - A with T and G with C. The binding of twocomplementary bases to form a ladder rung is called a base pair.Figure 7: Structure of nuclear <strong>DNA</strong>the human genomeThe human genome consists of approximately six billion base pairs along forty-six<strong>DNA</strong> molecules contained in twenty-three pairs of chromosomes in each cell nucleus.The order of bases along the <strong>DNA</strong> molecules is known as the <strong>DNA</strong> sequence.A gene is a particular area of a <strong>DNA</strong> molecule where the sequence of bases carriesinformation required to produce a particular protein from a particular sequence ofamino acids. Proteins provide the structural units for living organisms. Genes can varyin size, but average about 3,000 base pairs in length. Human <strong>DNA</strong> contains an estimated30,000 genes. Therefore, genetic or coding <strong>DNA</strong> makes up less than 5% of total human<strong>DNA</strong>. The remainder of the <strong>DNA</strong> is non-coding <strong>DNA</strong>.Some areas of non-coding <strong>DNA</strong> are consistent across all people, while other areasvary significantly between individuals. It is this variability that provides the basis fordistinguishing between individuals through <strong>DNA</strong> profiling.APPENDIX 3what is forensic dna profiling?PAGE 87