Biotechnology: King of Advanced Life Sciences

DNA Probes:                     The ability to isolate specific fragments of DNA containing known sequences of genes gives rise to DNA probes that can be used for a variety of diagnostic, forensic, and therapeutic purposes. DNA probes can be labeled with either radioactive or nonradioactive markers. A DNA probe has a strong interaction with (ideally) a specific DNA target and can be detected after the interaction. DNA probes consisting of 20 bases or fewer usually will have a unique target even in a large set of DNA molecules. The probability that any base will follow any other base in DNA is one in four or 0.25. Therefore, the probability of a specific sequence of 20 bases occurring in a DNA molecule by chance is 0.25 to the power of 20 a vanishingly small number. The use of DNA probes in various aspects of medical diagnostics is increasing rapidly.                       ...

Denaturation of DNA:        The three-dimensional structures of DNA, RNA, and proteins are determined by weak noncovalent interactions, principally hydrogen bonds and hydrophobic interactions. The free energies of these interactions are not much greater than the energy of thermal motion at room temperature, so that at elevated temperatures the structures of these molecules are disrupted. A macromolecule in a disrupted state is said to be denatured; the ordered state, which is presumably that originally present in nature, is called the native state. A transformation from the native to the denatured state is called denaturation.           When double-stranded (native) DNA is heated, the bonding forces between the strands are disrupted and the two DNA strands separate; thus, completely denatured DNA is single stranded. Much information about the structure and stabilizing interactions has been obtained by studying denaturation. Some p...

              The genetic information in all living cells is carried in molecules of deoxyribonucleic acid (DNA), which is primarily found in chromosomes. However, DNA is also present in cellular organelles such as mitochondria and chloroplasts. Viruses carry genetic information in either DNA or RNA molecules. When RNA viruses infect cells, the genetic information in RNA is converted to DNA prior to the replication and synthesis of new viral particles. In the case of certain RNA viruses (retroviruses) such as human immunodeficiency virus (HIV), the DNA that is copied from the infecting RNA is permanently integrated into the host chromosomes and the viral genome becomes an integral part of the cell’s genetic information. The structure of DNA was explained by James Watson and Francis Crick in the year 1953. The structure they proposed made it apparent for the first time how genetic information in chemically stored in cells and how it is replicated and...