Gene Cloning and DNA Analysis

Known world-wide as the standard introductory text to this important and exciting area, the fifth edition of Gene Cloning and DNA Analysis addresses new and growing areas of research whilst retaining the philosophy of the previous editions. Assuming the reader has little prior knowledge of the subject its importance, the principles of the techniques used and their applications are all carefully laid out, with over 250 clearly presented two-colour illustrations.

In addition to a number of informative changes to the text throughout the book, the final four chapters have been significantly updated and extended to reflect the striking advances made in recent years in the applications of gene cloning and DNA analysis in biotechnology:
Extended chapter on agriculture including new material on glyphosate resistant plants
New section on the uses of gene cloning and PCR in archaeology
Coverage of ethical concerns relating to pharming, gene therapy and GM crops
Gene Cloning and DNA Analysis remains an essential introductory text to a wide range of biological sciences students; including genetics and genomics, molecular biology, biochemistry, immunology and applied biology. It is also a perfect introductory text for any professional needing to learn the basics of the subject. All libraries in universities where medical, life and biological sciences are studied and taught should have copies available on their shelves.

Collagen

Collagens are found in tendons and other connective ligaments. Collagens have a triple helix as the major structure.The keratin structure is described more fully in the next section. The main differences in various keratins arises from their sulfur content. If there are many cysteine disulfide cross-links, then there is very little flexibility as in horns, claws, hooves, or nails. In wool, skin, and muscle proteins, there are fewer disulfide cross-links which allows some stretching but returns to normal upon relaxation of tension.

The quaternary structure of collagen consists of three left-handed helices twisted into a right-handed coil. This structure is shown in the graphic on the left.The basic properties of collagen are rigidity and resistance to stretching. The helices are grouped in a variety of more complex fiber type structures. A rigid pattern of interchain amide-carbonyl hydrogen bonding is best accommodated by a primary amino acid sequence of:

-gly-X-pro- or -gly-X-hypro

where X is any amino acid and hypro is hydroxyproline. In the graphic on the left X = arginine. Molecular model studies show that this sequence works the best for the triple helix structure. Glycine is needed because it is small and is the only amino acid which can fit in the interior of the triple helix.

Fibrous Proteins

Actually, the final beta-pleated sheet structure of silk is the result of the interaction of many individual protein chains. Specifically, hydrogen bonding on amide groups on different chains is the basis of beta-pleated sheet in silk proteins.

Quaternary Protein – Structure

The quaternary protein structure involves the clustering of several individual peptide or protein chains into a final specific shape. A variety of bonding interactions including hydrogen bonding, salt bridges, and disulfide bonds hold the various chains into a particular geometry. There are two major categories of proteins with quaternary structure - fibrous and globular

DNA Double Helix

The double-stranded helical model for DNA is shown in the graphic on the left. The easiest way to visualize DNA is as an immensely long rope ladder, twisted into a cork-screw shape. The sides of the ladder are alternating sequences of deoxyribose and phosphate (backbone) while the rungs of the ladder (bases) are made in two parts with each part firmly attached to the side of the ladder. The parts in the rung are heterocyclic amines held in position by hydrogen bonding. Although most DNA exists as open ended double helices, some bacterial DNA has been found as a cyclic helix. Occasionally, DNA has also been found as a single strand.