Chapter 33: Biotechnology and Human Disease

Overview In the past, efforts to understand genes and their expression have been confounded by the immense size and complexity of human deoxyribonucleic acid (DNA). The human genome contains approximately three billion (109) base pairs (bp) that encode 20,000 to 30,000 protein-coding genes located on 23 pairs of chromosomes. It is now possible to determine […]

Chapter 32: Regulation of Gene Expression

Overview Gene expression refers to the multistep process that ultimately results in the production of a functional gene product, either ribonucleic acid (RNA) or protein. The first step in gene expression—the use of deoxyribonucleic acid (DNA) for the synthesis of RNA (transcription)—is the primary site of regulation in both prokaryotes and eukaryotes. In eukaryotes, however, […]

Chapter 31: Protein Synthesis

Overview Genetic information, stored in the chromosomes and transmitted to daughter cells through DNA replication, is expressed through transcription to RNA and, in the case of messenger RNA (mRNA), subsequent translation into proteins (polypeptide chains, Figure 31.1). The pathway of protein synthesis is called translation because the “language” of the nucleotide sequence on the mRNA […]

Chapter 30: RNA Structure, Synthesis, and Processing

Overview The genetic master plan of an organism is contained in the sequence of deoxyribonucleotides in its deoxyribonucleic acid (DNA). However, it is through the ribonucleic acid (RNA)—the “working copies” of the DNA—that the master plan is expressed (Figure 30.1). The copying process, during which a DNA strand serves as a template for the synthesis […]

Chapter 29: DNA Structure, Replication, and Repair

Overview Nucleic acids are required for the storage and expression of genetic information. There are two chemically distinct types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA, see Chapter 30). DNA, the repository of genetic information, is present not only in chromosomes in the nucleus of eukaryotic organisms, but also in mitochondria and […]

Chapter 28: Vitamins

Overview Vitamins are chemically unrelated organic compounds that cannot be synthesized in adequate quantities by humans and, therefore, must be supplied by the diet. Nine vitamins (folic acid, cobalamin, ascorbic acid, pyridoxine, thiamine, niacin, riboflavin, biotin, and pantothenic acid) are classified as water-soluble, whereas four vitamins (vitamins A, D, K, and E) are termed fat-soluble […]

Chapter 27: Nutrition

Overview Nutrients are the constituents of food necessary to sustain the normal functions of the body. All energy is provided by three classes of nutrients: fats, carbohydrates, protein—and in some diets, ethanol (Figure 27.1). The intake of these energy-rich molecules is larger than that of the other dietary nutrients. Therefore, they are called macronutrients. This […]

Chapter 26: Obesity

Overview Obesity is a disorder of body weight regulatory systems characterized by an accumulation of excess body fat. In primitive societies, in which daily life required a high level of physical activity and food was only available intermittently, a genetic tendency favoring storage of excess calories as fat may have had a survival value. Today, […]

Chapter 25: Diabetes Mellitus

Overview of Diabetes Mellitus Diabetes mellitus is not one disease, but rather is a heterogeneous group of multifactorial, polygenic syndromes characterized by an elevation of fasting blood glucose caused by a relative or absolute deficiency in insulin. Diabetes is the leading cause of adult blindness and amputation, and a major cause of renal failure, nerve […]

Chapter 24: The Feed/Fast Cycle

Overview of the Absorptive State The absorptive (fed) state is the two- to four-hour period after ingestion of a normal meal. During this interval, transient increases in plasma glucose, amino acids, and triacylglycerols (TAG) occur, the latter primarily as components of chylomicrons synthesized by the intestinal mucosal cells (see Metabolism of chylomicrons). Islet tissue of […]