Plant Tissue Culture
Plant tissue culture broadly refers to the in vitro cultivation of plants, seeds and various parts of the plants (organs, embryos, tissues, single cells, protoplasts). The cultivation process is invariably carried out in a nutrient culture medium under aseptic conditions. History of Plant Tissue Culture Callus Culture Method German botanist Gottlieb Haberlandt (1902), regarded as […]
Antibody structure and function
The world is full of infectious microorganisms, all looking for a suitable host to infect. Bacteria, viruses, and protozoans are constantly attempting to gain entry into our tissues. If nothing was done about these attempts at invasion, no human could survive. Fortunately, cells of the immune system patrol the internal tissues, the bloodstream, and the […]
Transgenic Animals
NEW AND IMPROVED ANIMALS For thousands of years people have improved crop plants and domestic animals by selective breeding, mostly at a trial-and-error level. Woollier sheep and smarter sheep dogs have both been improved through many generations of selective breeding. Obviously, the more we know about genetics, the faster and more effectively we can improve […]
Cloning of Animals
Although the cloning of Dolly the sheep in 1996 created a major furor in the media, from a scientific viewpoint it was a relatively small step in a developing technology. Cloning animals relies on the technique of nuclear transplantation . This actually dates back to 1952 when nuclei from early frog embryos were transplanted into […]
Meselson–Stahl experiment
The first problem in understanding DNA replication was to figure out whether the mechanism of replication was semiconservative, conservative, or dispersive. In 1958, two young scientists, Matthew Meselson and Franklin Stahl, set out to discover which of these possibilities correctly described DNA replication. Their idea was to allow parental DNA molecules containing nucleotides of one […]
DNA Replication
The copying mechanism to which Watson and Crick referred is called semiconservative. The sugar-phosphate backbones are represented by thick ribbons, and the sequence of base pairs is random. Let’s imagine that the double helix is like a zipper that unzips, starting at one end (at the bottom in Figure 1) We can see that, if […]
DNA: the genetic material
Before we see how Watson and Crick solved the structure of DNA, let’s review what was known about genes and DNA at the time that they began their historic collaboration: 1. Genes— the hereditary “factors” described by Mendel—were known to be associated with specific character traits, but their physical nature was not understood. Similarly, mutations […]
Digestion of Proteins by Proteases
Proteases (also known as proteinases or peptidases ) hydrolyze the peptide bond between amino acid residues in a polypeptide chain. Proteases may be specific and limited to one or more sites within a protein, or they may be nonspecific, digesting proteins into individual amino acids. The ability to digest a protein at specific points is […]
Westren Blotting of Proteins
Often researchers will use Western blotting to identify proteins. Western blots rely on having an antibody to the protein. Antibodies are extremely specific and will bind only to one target protein. The first step is to separate the proteins by size by either standard SDS-PAGE or 2D-PAGE. The proteins are then transferred from the gel […]
Gel Electrophoresis OF Proteins
Studying proteins requires the ability to isolate and identify the proteins in a particular sample. The first step is to separate them. Much as electrophoresis on agarose gels is used to separate DNA by size, so polyacrylamide gel electrophoresis (PAGE) is used to separate proteins by size. Polyacrylamide has smaller pores than agarose and is […]