Chapter 1
Structure and Function of the Human Genome
FRIEDHELM HILDEBRANDT
Structure of Nucleic Acids
The term "molecular biology" refers to the biology of nucleic acids. Methods of molecular biology make in vitro use for experimental purposes of
naturally occurring mechanisms such as transcription or transformation.
Most techniques of molecular biology are based on two basic principles:
• The use of nucleic acid-modifying enzymes
• Hybridization (base pairing) between two complementary strands of nucleic acids.
DNA-rnodifying enzyrnes are used to cut DNA at specific sites (restriction
enzyme digestion) to recombine DNA fragments (ligation), or to amplify
and sequence DNA fragments with the help of polymerases. Hybridization
methods allow for specific selection of nucleic acid fragments of interest
through base pairing with a defined probe. The probe is labeled radioactively or non-radioactively for detection of the cognate hybridization fragment.
The size of the haploid human genome (i. e. its complexity) is approximately 3 x 10 9 nucleotides. Figure 1 shows an electron micrograph of a
metaphase chromosome, which has been treated with detergents leaving
only a remnant of the protein scaffold with DNA spillingout from the chromosomal backbone. This structure gives an impression of the dimensions
that we are dealing with when studying the sequences of individual nucleotide sequences with respect to the structure of a complete human chromosome, which measures approximately 10 8 nucleotides. In the following, the
structure of the human genome is discussed, starting with its smallest strucFriedhelm Hildebrandt, Universitäts-Kinderklinik, Mathildenstrasse 1, Freiburg, 79106,
Germany (phone +49-761-270-4301; fax +49-761-270-4533; e-mail hildebra@kkl200.ukl. uni-freiburg.de)
Structure and Function of the Human Genome
FRIEDHELM HILDEBRANDT
Structure of Nucleic Acids
The term "molecular biology" refers to the biology of nucleic acids. Methods of molecular biology make in vitro use for experimental purposes of
naturally occurring mechanisms such as transcription or transformation.
Most techniques of molecular biology are based on two basic principles:
• The use of nucleic acid-modifying enzymes
• Hybridization (base pairing) between two complementary strands of nucleic acids.
DNA-rnodifying enzyrnes are used to cut DNA at specific sites (restriction
enzyme digestion) to recombine DNA fragments (ligation), or to amplify
and sequence DNA fragments with the help of polymerases. Hybridization
methods allow for specific selection of nucleic acid fragments of interest
through base pairing with a defined probe. The probe is labeled radioactively or non-radioactively for detection of the cognate hybridization fragment.
The size of the haploid human genome (i. e. its complexity) is approximately 3 x 10 9 nucleotides. Figure 1 shows an electron micrograph of a
metaphase chromosome, which has been treated with detergents leaving
only a remnant of the protein scaffold with DNA spillingout from the chromosomal backbone. This structure gives an impression of the dimensions
that we are dealing with when studying the sequences of individual nucleotide sequences with respect to the structure of a complete human chromosome, which measures approximately 10 8 nucleotides. In the following, the
structure of the human genome is discussed, starting with its smallest strucFriedhelm Hildebrandt, Universitäts-Kinderklinik, Mathildenstrasse 1, Freiburg, 79106,
Germany (phone +49-761-270-4301; fax +49-761-270-4533; e-mail hildebra@kkl200.ukl. uni-freiburg.de)