Genetic Message Expression and Protein Synthesis
Expression of the Genetic Message
The expression of the genetic message is the process by which the information encoded in DNA is used to synthesize specific proteins. These proteins, including enzymes, are responsible for the structural and functional characteristics of an organism.
Codons
Each codon, a sequence of three nucleotides, captures a specific amino acid. AUG is the initiation triplet (methionine), meaning all proteins begin with it. UAA, UAG, and UGA are termination codons, signaling the
Read MoreThe Digestive System and Nutrition: A Comprehensive Guide
Feeding and Nutrition
Feeding
Feeding is the ingestion of food from our environment. Our diet consists of the food we select.
Nutrients
Nutrients are substances in food that provide us with the matter and energy necessary for our vital functions.
Characteristics of Food
Quantity
The amount of nutrients varies depending on the food. Bread and pasta are rich in carbohydrates, meat provides proteins, and lettuce and other green vegetables are good sources of vitamins.
Quality
Higher quality foods provide nutrients
Read MoreChromosome Theory of Inheritance & Linkage
Chromosome Theory of Inheritance
Early Research
In 1902, two researchers, Walter Sutton in the United States and Theodor Boveri in Germany, independently observed parallels between the inheritance of Mendelian hereditary factors and the behavior of chromosomes during meiosis and fertilization. They proposed that hereditary factors (genes) were located on chromosomes. This is known as the chromosome theory of inheritance, or the Sutton-Boveri theory.
In 1909, William Bateson introduced the term “genetics”
Read MoreEpithelial, Connective, Muscle, and Nervous Tissues: An Overview
Epithelial Tissue
Epithelial tissue lines the body’s exterior and internal surfaces of hollow organs, including those of the respiratory, digestive, urinary, and reproductive systems. Its primary function is protection and selective barrier formation, regulating substance passage. This non-vascularized tissue receives nutrients via diffusion from adjacent vascularized tissue.
Glandular Epithelial Tissue
During embryonic development, some epithelial cells specialize in secretion, forming glands. These
Read MoreSmooth Muscle Pharmacology and Drug Interactions
Smooth Muscle Relaxation
Increasing cAMP or cGMP → PKA or PKG → phosphorylation of MLCK or phosphorylation of VOCCs. This phosphorylation prevents MLCK from phosphorylating MLC (reducing the amount of phosphorylated MLC) → ↓ [Ca2+] → This is a powerful “anti-contraction” mechanism → relaxation.
Smooth Muscle Contraction
Release of Ca2+ from intracellular stores → calcium-calmodulin complex. This activates myosin light chain kinase (MLCK), leading to phosphorylation of MLC (myosin light
Epithelial Cell Junctions and Specializations
Apical Specializations
Microvilli
Microvilli are cylindrical, membrane-bound cytoplasmic extensions that increase the absorptive surface of cells without increasing cell volume. They are abundant in organs involved in substance exchange. A collection of microvilli is called a brush border. Microvilli are classified into two types based on their arrangement: orderly and disorderly (or accidental). They have a diameter of 0.1μm and a length of 0.6 to 0.8μm, observable with electron microscopy.
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