Razzaq Archive

Epistasis

In trying to find evidence of gene interaction, one approach is to look for cases of a type of gene interaction called epistasis. This word means “stand upon,” referring to the ability of a mutation at one locus to override …

Recessive Lethal Alleles

Many mutant alleles are capable of causing the death of an organism; such alleles are called lethal alleles. The human disease alleles provide examples. A gene whose mutations may be lethal is clearly an essential gene.The ability to determine whether …

Protein Synthesis Inhibitors

Many antibiotics inhibit protein synthesis by binding with the bacterial ribosome and other components of protein synthesis. Because these drugs discriminate between bacterial and eukaryotic ribosomes, their therapeutic index is fairly high but not as high as that of cell …

Cell wall Inhibitor

Penicillins Most penicillins (e.g., penicillin G or benzylpenicillin) are derivatives of 6-aminopenicillanic acid and differ from one another with respect to the side chain attached to the amino group. The most crucial feature of the molecule is the B-lactam ring, …

Characteristics of Antimicrobial Drugs

As Ehrlich so clearly saw, a successful chemotherapeutic agent has selective toxicity: it kills or inhibits the microbial pathogen while damaging the host as little as possible. The degree of selective toxicity may be expressed in terms of (1) the …

Penicillin

Penicillin, the first true antibiotic because it is a natural microbial product, was first discovered in 1896 by a twenty-one-yearold French medical student named Ernest Duchesne. His work was forgotten until Alexander Fleming accidentally rediscovered penicillin in 1928. After returning …

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 …

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 …

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) …

Proteomics

Today we have the genome sequences for humans as well as many other animals, plants, fungi, and bacteria. All these data have given scientists a global view of the various genes in humans and others. However, genes are only the …