Abdul Archive
Mitosis is a type of cell division in which one cell (the mother) divides to produce two new cells (the daughters) that are genetically identical. The mitosis is a part of somatic cell division which includes the division of the …
Genes act by controlling cellular chemistry. Early in the twentieth century, Archibald Garrod, an English physician, made the first observation supporting this insight. Garrod noted that several recessive human diseases show defects in what is called metabolism, the general set of chemical …
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. …
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 . …
Human matings, like those of experimental organisms, provide many examples of single-gene inheritance. However, controlled experimental crosses cannot be made with humans, and so geneticists must resort to scrutinizing medical records in the hope that informative matings have been made (such …
It might be expected that bacterial cells, being small and relatively simple, would be uniform in shape and size. This is not the case, as the microbial world offers considerable variety in terms of morphology. However, the two most common …
Pathogenic microbes, though relatively few in number, have had and continue to have considerable impact on humans. Thus one of the most active and important fields in microbiology is medical microbiology, which deals with diseases of humans and animals. Medical …
Although Fracastoro and a few others had suggested that invisible organisms produced disease, most people believed that disease was caused by supernatural forces, poisonous vapors called miasmas, and imbalances among the four humors thought to be present in the body. …
The earliest microscopic observations of organisms appear to have been made between 1625 and 1630 on bees and weevils by the Italian Francesco Stelluti (1577-1652), using a microscope probably supplied by Galileo (1564-1642). Robert Hooke (1635-1703) is credited with publishing …
Microorganisms are defined as those organisms and acellular biological entities too small to be seen clearly by the naked eye They are generally 1 millimeter or less in diameter. Although small size is an important characteristic of microbes, it alone …