Biology questions and answers G

Biology G

What is gall (hypertrophies) ?

An abnormal swelling, growth, or tumor found on certain meristematic (growing) plant tissues caused by another organism such as parasites, insects, bacteria, fungi, viruses, injuries, or chemicals. There are hundreds of types of galls, and insects and mites are the most common organisms that cause them. The plant interacts with the attacking organism and provides raw materials to construct the gall via abnormal tissue growth. Many galls provide food and protective housing for various species of insects, and the resulting larvae that hatch are used as food by birds. Galls have been used for dyes, tannin for leather processing, medicines, and even food. There are over 1,400 species of insects that produce galls, and these insects collectively are called cecidozoa. Gallic acid was first isolated from oak leaf galls by the Swedish chemist Karl Scheele in 1786.

Who was Galton, Sir Francis ?

Galton, Sir Francis (1822–1911) British Anthropologist, Explorer Francis Galton has the distinction of being the half cousin of another prominent scientist of the 19th century, Charles Darwin. Galton is known as the founder of biometry and eugenics.

He was born in 1822, the youngest of seven children, into a wealthy Quaker family in Sparkbrook, near Birmingham, to Samuel Tertius Galton, a banker, and Frances Anne Violetta Darwin, the half sister of the physician and poet Erasmus Darwin, father of Charles Darwin, who would later influence greatly the mind of Francis.

He was homeschooled by his invalid sister Adele until he was five and was reading at an early age, appearing to have close to instant recall. He later attended King Edward’s School in Birmingham between 1836 and 1838, and then became an assistant to the major surgeon in the general hospital of that city at age 16. He continued his medical education by attending King’s College in London, and by 1840 he was attending Trinity College in Cambridge, although his attention was moving from medicine to mathematics. He never finished his studies due to a nervous breakdown and the stress from taking care of a terminally ill father.

By 1865 Galton had become keenly interested in genetics and heredity and was influenced by his cousin Charles Darwin’s On the Origin of Species in 1859. In Galton’s Hereditary Genius (1869) he presented his evidence that talent is an inherited characteristic. In 1872 he took on religion with Statistical Inquiries into the Efficacy of Prayer. Dalton created the study of eugenics, the scientific study of racial improvement, and a term he coined, to increase the betterment of humanity through the improvement of inherited characteristics, or as he defined it: “the study of agencies, under social control, that may improve or impair the racial qualities of future generations, either physically or mentally.” His thoughts on improving human society became widely admired.

Galton contributed to other disciplines and authored several books and many papers. In fact, between 1852 and 1910, he published some 450 papers and books in the fields of travel and geography, anthropology, psychology, heredity, anthropometry, statistics, and more. Twenty-three publications alone were on the subject of meteorology.

He became interested in the use of fingerprinting for identification and published Finger Prints, the first comprehensive book on the nature of fingerprints and their use in solving crime. He verified the uniqueness and permanence of fingerprints, and suggested the first system for classifying them based on grouping the patterns into arches, loops, and whorls.

As late as 1901, close to 80 years old, he delivered a lecture “On the Possible Improvement of the Human Breed Under Existing Conditions of Law and Sentiment,” to the Anthropological Institute, and he even returned to Egypt for one more visit. He published his autobiography, Memories of My life, in 1908 and was knighted the following year. Galton received a number of honors in addition to the ones already cited. He was a member of the Athenaeum Club (1855). He received honorary degrees from Oxford (1894) and Cambridge (1895) and was an honorary fellow of Trinity College (1902). He was awarded several medals that included the Huxley Medal of the Anthropological Institute (1901), the Darwin-Wallace Medal of the Linnaean Society (1908), and three medals from the Royal Society: the Royal (1886), Darwin (1902), and Copley (1910) medals.

Galton lived with a grandniece in his later years, and a month short of his 89th birthday, in 1911, his heart gave out during an attack of bronchitis at Grayshott House, Haslemere, in Surrey. He is buried in the family vault at Claverdon, near Warwick, Warwickshire. Galtonia candicans, a white bell-flowered member of the lily family from South Africa, and commonly known as the summer hyacinth, was named for Galton in 1888.

What is gametangium ?

A reproductive organ that produces gametes (reproductive cells); nuclei that fuse and produce sexual spores in algae, fungi, mosses, and ferns.

What is gamete ?

A haploid (half the number of chromosomes) sex cell, either male (sperm) or female (egg), that fuses with another sex cell during the process of fertilization.

What is gametophyte ?

For plants with alternation of generations, the gametophytic generation has haploid nuclei and generates gametes during mitosis.

What is ganglion ?

A knot or cyst of fibrous material in fluid in joints and tendons; also a cluster of nerve cells located outside the central nervous system. In invertebrates, ganglia and nerve bundles make up the central nervous system.

What is gap junction ?

A site between two cells that allows small molecules or ions to cross through and connect between the two cytoplasms; allows electrical potentials between the two cells.

What is gastrin ?

A hormone (linear peptide) produced and regulated by the pyloric gland area of the stomach that stimulates the secretion of gastric acids from the stomach walls and duodenum after eating. It is synthesized in G cells in the gastric pits located in the antrum region of the stomach. It occurs in the body in several forms. Gastrin is released after the eating of food containing peptides, certain amino acids, calcium, coffee, wine, beer, and others.

Too much secretion of gastrin, or hypergastrinemia, is a cause of a severe disease known as ZollingerEllison syndrome, which affects both humans and dogs. It creates gastric and duodenal ulceration from excessive and unregulated secretion of gastric acid, but it is also commonly brought on by the action of gastrin-secreting tumors (gastrinomas), which develop in the pancreas or duodenum. The hormone also stimulates the proliferation of gastrointestinal cells and adenocarcinomas (cancer of glandular linings) of the gastrointestinal tract.

What is gastropod ?

The most successful and largest class of mollusks (phylum Mollusca). There are more than 35,000 living species, and about half that number in the fossil record. Most gastropods travel by using a large flattened muscular foot and are univalve (onepiece shell), although a few have no shell. Gastropods have a defined head with a mouth and one or a pair of sensory tentacles. Examples of gastropods are snails and slugs.

What is gastrovascular cavity ?

A body cavity in certain lower invertebrates such as cnidarians and flatworms that serves for both digestion and circulation. It has a single opening that serves as both mouth and anus. Since lower invertebrates do not have a circulatory system, it also functions to distribute nutrients to cells that line the cavity.

What is gastrula ?

An animal embryo in an early stage of development, between blastula and embryonic axes, forming the characteristic three cell layers of endoderm, mesoderm, and ectoderm, and which will give rise to all of the major tissue systems of the adult animal.

What is gastrulation ?

The rearrangement of the germ layers by the blastoderm during animal development to the new positions in the embryo that will produce the three primary germ layers of endoderm, mesoderm, and ectoderm.

What is gated ion channel ?

A specific ion channel that opens and closes to allow the cell to alter its membrane potential. An ion channel is a membrane protein that forms an aqueous pore so that charged ions can cross through the membrane. There are several types of ion channels. For example, a ligand-gated ion channel is where gating is controlled by binding of a chemical signal (the ligand) to a specific binding site on the channel protein. Other ion channels are voltage gated and mechanically gated.

What is gel electrophoresis ?

The analytical laboratory process to separate molecules according to their size. The sample is put on an end of a slab of polymer gel, alyophilic colloid that has coagulated to a jelly. An electric field is applied through the gel, which separates the molecules; small molecules pass easily and move toward the other end faster than larger ones. Eventually all sizes get sorted, since molecules with similar electric charges and density will migrate together at the same rate. There are several types of gel composition, and various chemicals can be added to help separation.

What is gene ?

Structurally, a basic unit of hereditary material; an ordered SEQUENCE of NUCLEOTIDE bases that encodes one polypeptide chain (via mRNA). The gene includes, however, regions preceding and following the coding region (leader and trailer) as well as (in EUKARYOTES) intervening sequences (INTRONs) between individual coding segments (EXONs). Functionally, the gene is defined by the cis-trans test that determines whether independent MUTATIONs of the same phenotype occur within a single gene or in several genes involved in the same function.

What is genealogy ?

The study of one’s family and finding and recording the complete history of all ancestors within that family.

What is gene amplification ?

The selective increase or production of multiple copies of a specific gene in an organism without a proportional increase in others; specific DNA sequences are replicated disproportionately greater than their representation in the parent molecules. For example, a tumor cell amplifies, or copies, DNA segments naturally as a result of cell signals or sometimes because of environmental events.

What is gene cloning ?

A method for making identical copies of a particular DNA; the process of asexually synthesizing multiple copies of a particular DNA sequence, or cells (clones), using a bacteria cell or another organism as a host. The clones are genetically identical to the parent or donor cells. Cloning is used for biomedical research in the form of extracting stem cells in humans with the hope of gaining knowledge on the development of and cure for human diseases. Cloning for producing children and for medical research is controversial, and the ethics of such practices are being debated constantly

What is gene expression ?

A term describing the process of translating information in DNA into an organism’s traits. A process by which a gene’s code affects the cell in which it is found by synthesizing a protein or RNA product that exerts its effects on the phenotype of the organism. Expressed genes are transcribed into mRNA and translated into protein or transcribed into mRNA but not translated into protein.

What is gene flow ?

The exchange of genes between different but usually related populations. Gene flow happens when an individual or group of individuals migrates from one population to another, or vice versa, and interbreeds with its members.

What is gene pool ?

The total genetic information in all the genes and combinations in a breeding population at a given time.

What is generation time ?

The time needed to complete one generation. A generation spans from a given stage in a life cycle to the same stage in the offspring.

What is gene therapy ?

A treatment of disease, to correct genetic disorders, by replacing damaged or abnormal genes with new normal ones, or by providing new genetic instructions to help fight disease through the use of recombinant DNA technology. Therapeutic genes are transferred into the patient via a weakened virus, a nonviral vector, or direct delivery of “naked” DNA. Germ line or heritable gene therapy is used for modification of reproductive cells. Somatic cell or noninheritable gene therapy involves those other than reproductive cells.

What is genetic code ?

The language of genetics. The instructions in a gene that tell the cell how to make a specific protein. The code defines the series of nucleotides in DNA, read as triplets called codons, that specifies the sequence of amino acids in a protein. The set comprises 64 nucleotide triplets (codons) that specify the 20 amino acids and termination codons (UAA, UAG, UGA).

The code is made up of adenine (A), thymine (T), guanine (G), and cytosine (C), the nucleotide bases of DNA. Each gene’s code combines them in various ways to spell out three-letter triplets (codons) that specify which amino acid is needed at each step in making a protein.

What is genetic drift ?

Random changes in allele frequency over time from one generation to another as the genetic makeup of a population drifts at random over time instead of being shaped by natural selection in a nonrandom way. Especially prevalent in small populations, where a particular allele can be eliminated by chance and certain alleles can be favored over time. This can lead to the loss of genetic variability.

What is genetic engineering ?

A process that changes the genetic makeup of cells. During the process a gene is isolated, modified, and put back into an individual of the same or different species. The process can be used to introduce or eliminate specific genes. Used in agriculture where plants can be genetically engineered to resist a pest.

What is genetic map (DNA map) ?

A chromosome map that shows the order of and distance between genes. Useful for finding inherited diseases by following the inheritance of a DNA marker present in affected individuals. Genetic maps have been used to find the exact chromosomal location of disease genes, including cystic fibrosis, sickle-cell disease, Tay-Sachs disease, fragile X syndrome, and myotonic dystrophy. Genetic maps can be cytogenetic, linkage, or physical. A cytogenetic map produces a visual appearance of a chromosome when stained and examined under a microscope. Important are the visually distinct regions, called light and dark bands, that give each of the chromosomes a unique appearance. A linkage map is a map of the relative positions of genetic loci on a chromosome, determined on the basis of how often the loci are inherited together. Distance is measured in centimorgans (cM). A physical map of a species shows the specific physical locations of its genes and/or markers on each chromosome.

What is genetic recombination ?

The process where offspring have a different genotype from that of the parent due to the recombining of genetic materials, usually caused by crossing over between homologous chromosomes during meiosis, or random orientation of nonhomologous chromosomes pairs, gene conversion, or other means. It occurs during the cell division (meiosis) that occurs during the formation of sperm and egg cells. This shuffling of genetic material increases the potential for genetic diversity.

What is genetics ?

The scientific study of heredity and variation.

What is genome ?

The complete assemblage of chromosomes and extrachromosomal genes of a cell, organelle, organism, or virus; the complete DNA portion of an organism; the complete set of genes shared by members of any reproductive body such as a population or species.

What is genomic imprinting ?

Occurs when DNA receives biochemical marks instructing a cell how and when to express certain genes. Resulting gene expression is usually from one copy of a gene, either from the maternal or paternal gene.

What is genomic library ?

A collection of clones made from a set of randomly generated overlapping DNA fragments that represents the entire genome of an organism.

What is genotype ?

The complete genetic makeup of an organism, which may not show in physical appearance; the pair of alleles at a particular locus. The percentage of a particular genotype in a population is called the genotype frequency. Also, in taxonomy, the type species of a genus.

What is genus ?

Taxonomic classification of a group of related or similar objects or organisms. A genus has one or more species. Groups of similar genera, plural of genus, make up a family. In the scientific name of an organism, it is the first word followed by a second word to complete the binomial. For example, Homo is the genus name for humans, while the entire binomial, Homo sapiens, is the species name. Genus and species names are italicized.

What is geographic range ?

The total area or range occupied by a species or population.

What is geological time ?

The span of time that has passed since the creation of the Earth and its components; a scale used to measure geological events millions of years ago. Measured in chronostratic or relative terms, where subdivisions of the Earth’s geology are set in an order based on (a) relative age relationships based on fossil composition and stratigraphic position or (b) chronometric or absolute time where the use of radiometric dating techniques give numerical ages.

What is geosynclines ?

A large, down-warped, generally linear basin or trough found in the Earth’s crust where large amounts of sediment and volcanic material have accumulated; can be folded into mountains. A miogeocline is a geosyncline in which volcanism is not associated with sedimentation.

What is geotropism (gravitropism) ?

A plant’s response to gravitational effects. A plant’s roots grow downward toward the gravitational pull, a characteristic called positive geotropism, while shoots grow upward against gravitational pull, a feature referred to as negative geotropism.

What is germination ?

Sprouting of a seed; the first stages in the growth of a seed from a seedling to an adult. After germination the embryonic shoot emerges and grows upward while the embryonic root grows downward. Food for germination is located in the endosperm tissue within the seed and or seed leaves. Sprouting of pollen grains on a stigma and growth of fungus or algal spores are examples of germination.

What is gestalt ?

Grasping an overall concept without understanding the details; perceiving the whole or patterns over that of the pieces, e.g., the tune of a song. It is based on an object or thing, its context in the environment, and the relationship between it all. Gestalt is German for configuration or figure.

What is gibberellins ?

A group of about 50 hormones or growth regulators that primarily stimulate cell division and elongation in plants. Gibberellic acid (GA), the first of this class to be discovered, causes extreme elongation (bolting) of stems. Gibberellins are also involved in flower, fruit, and leaf enhancements, germination, and vernalization (temperature effects).

What is giemsa stain ?

Stains developed specifically for the phosphate groups of DNA in which the staining of chromosomes produces light and dark bands characteristic for each chromosome, called g-bands. Each homologous chromosome pair has a unique pattern of g-bands, enabling easy recognition of particular chromosomes. Also used for looking for Schuffner’s dots, which are small, red-staining granules in red-bloodcell cytoplasm infected with either Plasmodium vivax or P. ovale.

What is gigantism ?

Animals that evolve on islands are affected by gigantism or dwarfism, the evolution of body form as either large (e.g., Komodo dragon weighs up to 365 pounds) or small (e.g., Island fox in Channel Islands). Island animal populations tend to acquire different sizes from their mainland counterparts. Gigantism is also the condition of too much growth hormone production in humans where people grow taller than normal.

What is gill ?

A respiratory organ in aquatic animals; an outfold of epidermal tissue; the gas-exchange surface of many aquatic animals; a filamentous outgrowth with blood vessels where gas exchanges (oxygen and carbon dioxide) between water and blood. A bony structure supporting the gill filaments is called the gill arch. A flap of bony plates that cover the gills of bony fish is called the gill cover, or operculum.

In fish, gill slits are openings or clefts between the gill arches. Water is taken in by the mouth and then passes through the gill slits and bathes the gills. Gills are also rudimentary grooves in the neck region of embryos of air-breathing vertebrates like humans. A gill is also the part of fungi that contains the basidia, the reproductive cell (meiotangium) that typically produces four spores on the outside.

What is gizzard ?

Part of an animal gut, e.g., in birds, that is specialized for grinding and mixing food with digestive enzymes. Also called the gastric mill.

What is glaciation ?

A long period of time characterized by climatic conditions associated with maximum expanse of ice sheets. The process of glaciers spreading over the land. In North America, the most recent glacial event is the Wisconsin glaciation, which began about 80,000 years ago and ended around 10,000 years ago. Most glacial ice today is found in the polar regions, above the Arctic and Antarctic Circles.

What is gland ?

A group of cells (organ), or a single cell in animals or plants, that is specialized to secrete a specific substance such as a hormone, poison, or other substance. Two types of animal glands are endocrine and exocrine. Endocrine glands place their products directly into the blood stream, while exocrine use a duct or network into the body. Glands important to the human body are the hypothalamus, which secretes hormones to regulate the pituitary gland; the pineal gland, which secretes melatonin, a hormone that deals with daily biological rhythms; the pituitary gland, which secretes hormones that influence other glands and organs that deal with growth and reproduction; the thyroid gland, which regulates metabolism and blood calcium levels; the parathyroid gland, which regulates the use of calcium and phosphorus; the thymus gland, which stimulates the immune system’s T cell development; the adrenal gland, which secretes the male hormone, androgens, and aldosterone, which helps maintain the body’s salt and potassium balances, and epinephrine (adrenaline) and norepinepherine (noradrenaline); the pancreas gland, which secretes insulin, which controls the use of sugar in the body, and other hormones involved with sugar metabolism; the ovaries, which secrete female hormones such as estrogen, which maintains female traits, and progesterone for pregnancy; the eccrine gland, whose excretory canal emerges directly onto the skin’s surface; the exocrine gland, which secretes products that get directly eliminated, at the level of the skin, or through a mucous membrane; and the holocrine gland, whose secretions result from the destruction of the cells forming it.

A plant gland is usually a bump, depression, or appendage on the surface or within that produces a sticky or greasy viscous fluid such as oil or resin. The floral nectary is a gland in the flower that secretes a sugary fluid that pollinators utilize for food, while the extrafloral nectary is a gland on the nonflower part that secretes a sugary fluid that serves the same purpose. A gland-dot is a tiny pore that secretes fluid; glandular hairs bear glands. Oil glands can often be seen on a plant’s areole, and irregular (not round) leaf oil glands can be either an island oil gland that is not connected to veinlets or an intersectional oil gland that is connected to veinlets.

What is glaucoma ?

A disease of the eye characterized by loss of vision due to an increase in the pressure of fluid within the eye (intraocular pressure) that leads to damage to the optic nerve and loss of vision in both eyes. Can eventually lead to blindness. The disease affects about 6 million people worldwide. In the United States, about 3 million people are affected.

What is glial cell ?

Nonimpulse-conducting cells that make up half the weight of the brain; in the central nervous system they are 10 times as numerous as neurons and act as support cells by forming insulation around the neurons to protect them. Their support functions provide myelin for axons, and they act as housekeepers after cell damage or death by cleaning up. Glial cells also play an important role in the early and continuing development of the brain. A small hormonelike protein, called the glial growth factor, induces the growth of glial cells. A type of brain tumor that forms in the glial tissue is called glioblastoma multiform.

There are several types of glial cells in the central nervous system, including oligodendrocytes, astrocytes, and microglia. It is the oligodendrocytes that produce the fatty protein myelin that insulates the axons by wrapping them in layers of myelin. Star-shaped astrocytes lay down scar tissue on damaged neurons and hold the neurons in place as well as supply potassium and calcium and regulate neurotransmitter levels. Along with microglia cells, astrocytes remove dead cells and other matter from the central nervous system.

Similar functionary types of cells in the peripheral nervous system are the Schwann (provide insulation via myelin) and satellite cells (support cells).

A debilitating disease caused by the demyelinating of neurons is multiple sclerosis, and stem-cell research is being conducted into developing new treatments.

What is glomerulus ?

A structure, a tiny ball, between the afferent arterioles and efferent arterioles within the proximal part of the nephron of the kidney; located within the Bowman’s capsule. It is composed of a cluster of capillary blood vessels and is involved in the filtration of blood. The glomerulus is a semipermeable structure that allows water and soluble wastes to pass through and then discharges them out of the Bowman’s capsule as urine waste at a rate of about 160 liters or 42.7 gallons per 24-hour period. Most of this is reabsorbed back into the blood. The filtered blood then leaves the glomerulus by way of the efferent arteriole to the interlobular vein. Each kidney contains about 1 million glomeruli. Changes in the glomerulus may be responsible for diabetic kidney disease.

Also a nest of nerves in invertebrates found in invertebrate olfactory processing centers; a discrete, globular mesh of densely packed dendrites and axons found in the vertebrate olfactory bulb.

What is glucagon ?

A protein hormone released by the pancreas via alpha cells in the islets of Langerhans with the purpose of breaking down glycogen, in the liver, which releases glucose and increases blood levels of glucose. Glucagon works with insulin to maintain normal blood sugar levels.

What is glucocorticoid ?

A class of stress-related steroids (hormones) produced by the adrenal glands (cortex) that respond to the stimulation by adrenocorticotropic hormone (ACTH) that comes from the pituitary gland. They are involved in carbohydrate, lipid, and protein metabolism by promoting gluconeogenesis and the formation of glycogen, as well as effects on muscle tone, circulation, blood pressure, and more. They possess antiinflammatory and immunosuppressive properties. Cortisol (hydrocortisone) is the major natural glucocorticoid.

Synthetically produced ones—mostly derived from cortisol, such as cortinsone, prednisone, prednisolone, methylprednisolone, betamethasone, and dexamethasone—regulate metabolism of lipids, carbohydrates, and protein and work without the use of ACTH.

Glucocorticoids also cause osteoporosis, weight gain, cataracts, heart disease, diabetes, and psychosis.

What is glucose ?

A form of six carbon sugar (C6H12O6) that is the most common energy source and is the usual form in which carbohydrates are assimilated by animals. It is carried through the bloodstream and is made not only from carbohydrates but from fats and protein as well. Glucose is known as a dextrorotatory sugar (a chiral molecule that rotates plane-polarized light to the right), which is sweet, colorless, and soluble.

What is glycocalyx ?

A thick, (7.5–200 nm) extracellular, sticky coating of oligosaccharides linked to plasma membrane glycoprotein and glycolipids; found around the outside of eukaryote cells, and used to adhere to surfaces. Also called the cell coat.

What is glycogen ?

A large polysaccharide; stored energy found in the muscles and liver. It consists of many monosaccharide glucose molecules linked together and is used as a fuel during exercise, broken down as needed; glycogen is the primary storage form of glucose in animals. Also known as stored sugar or animal starch.

What is glycolysis ?

The anaerobic pathway or enzymatic conversion (using 11 different enzymes) in the cell’s cytoplasm of glucose to simpler compounds. Glucose, a six-carbon sugar, is converted into two molecules of pyruvic acid of three carbons each, with two molecules of NADH and two ATPs as by-products. It is the most universal and basic energy harvesting system; it transforms glucose into lactic acid in muscles and other tissues for energy production when there is not enough oxygen available.

In aerobic respiration, the two pyruvic acids are further used in the KREBS CYCLE.

What is glycoprotein (conjugated protein) ?

Glycoproteins are complexes in which carbohydrates are attached covalently to asparagine (N-glycans) or serine/threonine (Oglycans) residues of peptides. A protein coated with a sugar is termed glycosylated and is described or named with the initials “gp” along with its molecular weight, e.g., gp160. Several gps are associated with HIV infection, since they are the outer-coat proteins of HIV: gp41 plays a key role in HIV’s infection of CD4+ T cells by facilitating the fusion of the viral and cell membranes. The protein gp120 is one of the proteins that forms the envelope of HIV; it projects from the surface of HIV and binds to the CD4 molecule on helper T cells. GPs are found in mucus and mucins, y-globulins, a1-globulins, a2-globulins, and transferrin, an iontransporting protein. They act as receptors for molecular signals originating outside the cell. Attachment of oligosaccharides to peptides increases solubility, covers the antigenic domains, and protects the peptide backbone against proteases.

What is gold drugs ?

Gold COORDINATION compounds used in the treatment of rheumatoid arthritis, examples being auranofin, (tetraacetylthioglucosato-S)(triethylphosphane)gold(I), and myocrisin, disodium thiomalonatogold(I).

Who was Golgi, Camillo ?

Golgi, Camillo (1843–1926) was Italian Medical Teacher Camillo Golgi was born in Corteno, near Brescia, Italy, on July 7, 1843, the son of a physician. He studied medicine at the University of Pavia, and after graduating in 1865, he continued working in Pavia at the Hospital of St. Matteo. Golgi was influenced by the scientific methods of Giulio Bizzozero, who introduced general pathology in the programs of the medical school at the University of Pavia. In 1872 Golgi accepted the post of chief medical officer at the Hospital for the Chronically Sick at Abbiategrasso and began his investigations into the nervous system.

Golgi returned to the University of Pavia as extraordinary professor of histology, left the university, and returned as the chair for general pathology in 1881, succeeding his teacher Bizzozero. He also married Donna Lina, a niece of Bizzozero.

Golgi developed an interest in the causes of malaria and determined the three forms of the parasite and their associated fevers. He developed a photographic technique to document the most characteristic phases of malaria in 1890.

While Golgi never practiced medicine, he was a famous and popular teacher as director of the Department of General Pathology at St. Matteo Hospital. He also founded and directed the Instituto SieroterapicoVaccinogeno of the Province of Pavia. Golgi also became rector of Pavia University and was made a senator of the Kingdom of Italy.

During World War I, he assumed the responsibility for a military hospital in Pavia and created a neuropathological and mechanotherapeutical center for the study and treatment of peripheral nervous lesions and for the rehabilitation of the wounded.

His greatest contribution seems to be his revolutionary method of staining individual nerve and cell structures, known then as the “black reaction” and now called Golgi staining. It allowed a clear visualization of a nerve cell body with all its processes.

Golgi shared the Nobel Prize for 1906 with Santiago Ramón y Cajal for their work on the structure of the nervous system. He retired in 1918 but remained as professor emeritus at the University of Pavia. The Historical Museum at the University of Pavia dedicated a hall to Golgi, where more than 80 certificates of honorary degrees, diplomas, and awards are exhibited.

Golgi’s discovery of the black reaction and further research provided a major contribution to the advancement of the knowledge on the structural organization of nerve tissues. He also described the morphological features of glial cells and the relationships between their processes and blood vessels; described two fundamental types of nerve cells today called Golgi type I and Golgi type II; discovered the Golgi tendon organs; explained the cycle of plasmodium (malaria) and the cell organelle, today called the Golgi apparatus.

Golgi died at Pavia on January 21, 1926. In 1994 the Italian Ufficio Principale Filatelico issued a stamp to celebrate his work.

What is Golgi apparatus or complex ?

Part of a cell, a cup- or disclike organelle in cells, usually near the nucleus and composed of a number of flattened or folded sacs, called cisternae, with vacuoles and vesicles. They act as an assembly line in sorting, modifying, and packaging proteins and lipids produced on the endoplasmic reticulum,located in the cytoplasm of the cell, for various parts of the cell. Named after the Nobel Prize recipient, Italian neurologist and histologist Camillo Golgi (1843–1926). They are the formation site of the carbohydrate side chains of GLYCOPROTEINS and mucopolysaccharides. The vacuoles release these by migrating through the cell membrane. Some of the vesicles send molecules to the cellular membrane, where they are excreted, and some are used for selective excretion.

What is gonadotropins ?

A group of hormones that are produced in the pituitary gland and regulate the development and function of the testis and ovary. The group includes the follicle-stimulating hormone (FSH), which promotes male and female gamete formation, and luteinizing hormone (LH), which stimulates the secretion of the male and female testosterone and estrogen. Gonadotropin itself is controlled by the gonadotropin releasing hormone (GnRH), a hormone that controls the production and release of gonadotropins and is secreted by the hypothalamus every 90 minutes or so, which enables the pituitary to secrete LH and FSH.

What is gonads ?

The male and female sex organs. In the male, they are glands located inside the scrotum, behind and below the penis, which produce sperm and are the primary source of testosterone. Also called the testes. In the female, they are ovaries, two almond-sized glands located on either side of the uterus. They produce and store the oocytes and the female sex hormones estrogen and progesterone.

What is Gondwanaland (Gondwana) ?

The large southern protocontinent, derived from the supercontinent Pangaea, that, when fragmented, formed Africa, South America, Antarctica, Australia, and India during the Paleozoic era more than 200 million years ago as an event of plate tectonics (continental drift).

What is G protein ?

A class of heterotrimeric proteins important in signaling pathways in the plasma membrane in mammalian cells. Regulated by the guanine nucleotides GDP (guanosine diphosphate) and GTP (guanosine triphosphate), they participate in cell signal pathways by usually binding a hormone or signal ligand to a seven-pass transmembrane receptor protein; activates intracellular messenger systems when the signaling molecule (typically a hormone) binds to the transmembrane receptor. The proteins are located on the inner surface of the plasma membrane and transmit signals from outside the membrane, via transmembrane receptors, to adenylate cyclase, which then catalyzes the formation of the second messenger, cyclic adenosine monophosphate (AMP), inside the cell.

What is graded potential ?

A nerve impulse that is initially proportional to the intensity of the stimulus that produces it, then declines in intensity; membrane potentials that vary in magnitude.

What is gradualism ?

An Earth model of evolution that assumes a slow, steady rate of change, with slow steps instead of quick leaps, and with new variation arising by mutation and recombination. A view held by Charles Darwin.

What is grafting ?

The process of attaching two different plant parts, usually shoots, to each other to create a single new plant. Used in propagating trees and shrubs.

What is Gram staining ?

An important laboratory technique to distinguish between two major bacterial groups, based on stain retention by their cell walls. Bacteria smears are fixed by flaming, then stained with crystal violet followed by iodine solution, and then rinsed with alcohol or acetone, decolorized, and counterstained with safranin. Gram-positive bacteria are stained bright purple or purple-black, while gram-negative bacteria are pink. This staining technique is useful in bacterial taxonomy and identification and in indicating fundamental differences in cell-wall structure. Gram-negative bacteria lack peptidoglycan in the cell wall, while gram-positive bacteria have about 90 percent of their cell wall composed of peptidoglycan.

What is granum ?

A series of disk- or saclike structures called thaylakoid disks—specialized membrane structures located in the inner membrane of chloroplasts—where photosynthesis takes place. They appear as green granules under a microscope and contain the light-reactant chemicals chlorophyll and carotenoid pigments. ATP is generated during photosynthesis by chemiosmosis.

What is gravid ?

Used in relation to pregnant insects and meaning heavy with fully developed eggs or denoting an advanced stage of pregnancy.

What is gravitropism ?

The ability of an organism or specific cells to respond, e.g., bend, to the gravitational pull; a growth curvature induced by gravity.

What is greenhouse effect ?

The warming of an atmosphere by its absorbing and reemitting infrared radiation while allowing shortwave radiation to pass on through.

Certain gaseous components of the atmosphere, called greenhouse gases, transmit the visible portion of solar radiation but absorb specific spectral bands of thermal radiation emitted by the Earth. The theory is that terrain absorbs radiation, heats up, and emits longer wavelength thermal radiation that is prevented from escaping into space by the blanket of carbon dioxide and other greenhouse gases in the atmosphere. As a result, the climate warms. Because atmospheric and oceanic circulations play a central role in the climate of the Earth, improving our knowledge about their interaction is essential.

What is gross primary productivity (GPP) ?

The total energy fixed by plants in a community through photosynthesis (such as repackaging inorganic energy to organic energy) per unit area per unit time; total carbon assimilation by plants; total mass or weight of organic matter created by photosynthesis over a defined time line.

What is ground meristem ?

Meristem is embryonic tissue. Ground meristem is one of the primary meristem tissues that are differentiated from the apical meristem. The primary meristem tissues include three different tissues: protoderm, ground meristem, and procambium. The protoderm differentiates into the epidermis; the procambium differentiates into the vascular tissue; and the ground meristem differentiates into three regions: the cortex, which is several layers of parenchyma cells under the epidermis of the stem and root; pith ray, the parenchyma cells between the vascular bundles in the primary dicot stem; and pith, which are parenchyma cells in the center of the primary dicot stem. Parenchyma are isodiametric cells, i.e., approximately equal in length, width, and height, that are thin walled and not extremely specialized. Ground meristem gives rise to cells of the ground tissue system. The ground tissue of a leaf, located between the upper and lower epidermis and specialized for photosynthesis, is called the mesophyll.

What is ground tissue system ?

The plant tissue system that forms most of the photosynthetic tissue in leaves, composed mostly of parenchyma cells and some collenchyma (elongate and thick walled in strands) and sclerenchyma (thick, rigid, secondary walls with lignin to provide support) cells. It is found between the epidermis and surrounding the vascular tissue system. Acts also as supporting tissue and in water and food storage.

What is growth factor ?

A complex family of organic chemicals, especially polypeptides, that bind to cell surface receptors and act to control new cell division, growth, and maintenance by the bone marrow.

Synthetic growth factors are being used to stimulate normal white blood cell production following cancer treatments and bone marrow transplants.

Examples of growth factors are insulin (including insulinlike growth factor (IGF), GF1, II, all of which are polypeptides similar to insulin); somatomedins, polypeptides made by the liver and fibroblasts that, when released into the blood (stimulated by somatotropin), help cell division and growth by incorporating sulfates into collagen, RNA, and DNA synthesis; HGH (human growth hormone), also called somatotropin, a proteinlike hormone from the pituitary gland that stimulates the liver to produce somatomedins that stimulate growth of bone and muscle; platelet-derived growth factor (PDGF), a glycoprotein that stimulates cell proliferation and chemotaxis in cartilage, bone, and other cell types; fibroblast growth factor, which promotes the proliferation of cells of mesodermal, neuroectodermal, epithelial, or endothelial origin; epidermal growth factor (EGF), important for cell development as it binds to receptors on cell surface to create a growth signal; and granulocyte colonystimulating factor (G-CSF), a growth factor that promotes production of granulocytes, a type of white blood cell.

What is guanylate cyclase ?

An ENZYME catalyzing the conversion of guanosine 5’-triphosphate to cyclic guanosine 3’,5’-monophosphate, which is involved in cellular REGULATION processes. One member of this class is a HEME-containing enzyme involved in processes regulated by nitrogen monoxide.

What is guard cell ?

Specialized epidermal cells; two crescentshaped cells on either side of the pore of a stoma in the stem or leaf epidermis. By changing shape, i.e., by opening and closing via changes in turgor, they regulate gas exchange and water loss by covering or uncovering the pore, which lets oxygen out and carbon dioxide in.

Who was Gullstrand, Allvar ?

Gullstrand, Allvar (1862–1930) was Swedish Ophthalmologist Allvar Gullstrand was born on June 5, 1862, in Landskrona and was the eldest son of Dr. Pehr Alfred Gullstrand, principal municipal medical officer, and his wife Sofia Mathilda Korsell. He was educated at schools in Landskrona and Jönköping, and he attended Uppsala University, but left in 1885 to spend a year at Vienna. He then continued his medical studies at Stockholm and presented his doctorate thesis in 1890. He was appointed lecturer in ophthalmology in 1891 and was appointed the first professor of ophthalmology at Uppsala University in 1894. He stayed in that position until 1914, when he was given a personal professorship in physical and physiological optics at Uppsala University, becoming an emeritus professor in 1927.

Gullstrand contributed a great deal to the knowledge of clinical and surgical ophthalmology and of the structure and function of the cornea of the eye, as well as research on astigmatism, and was self-taught in this area. He laid out his ideas in his doctoral thesis in 1890, Bidrag till astigmatismens teori (Contribution to the theory of astigmatism) and further refined them in Allgemeine Theorie der monochromatischen Aberrationen und ihre nächsten Ergebnisse für die Ophthalmologie (General theory of monochromatic aberrations and their immediate significance for ophthalmology), 1900; Die reelle optische Abbildung (The true optical image), 1906; and Die optische Abbildung in heterogenen Medien und die Dioptrik der Kristallinse des Menschen (The optical image in heterogeneous media and the dioptrics of the human crystalline lens), 1908. Further important works included Tatsachen und Fiktionen in der Lehre von der optischen Abbildung (Facts and fictions in the theory of the optical image), 1907; and Einführung in die Methoden der Dioptrik der Augen des Menschen (Introduction to the methods of the dioptrics of the human eyes), 1911.

In 1911 he invented the slit lamp and the reflexfree ophthalmoscope to help study the eye. He introduced a surgical technique for the treatment of symblepharon (a fibrous tract that connects the bulba conjunctiva to conjunctiva on the eyelid) and redefined the theory of accommodation. In 1911 he received the Nobel Prize for his research on dioptrics of the eye, although at first he declined it. Gullstrand died in Stockholm on July 28, 1930. Gullstrand is seen as one of the founders of modern ophthalmology.

What is guttation ?

A way for plants to expel water in excess of transpiration—principally through hydathodes, a special epidermal structure at the terminations of veins around the margins of the leaves—and especially under conditions of relatively high humidity. The expelled water appears on the ends of leaves mostly on moist cool nights and resembles dew.

What is gymnosperm ?

A group of flowerless plants that includes pines, conifers, redwoods, firs, yews, and cycads. Gymnosperm means “naked seed.” Their ovules and the seeds, which develop in them, are born unprotected on the surface of megasporophylls, and are often arranged on cones instead of being enclosed in ovaries as in the flowering plants. They release pollen directly into the air, which finds its way to female ovules and fertilizes them. The earliest examples of gymnosperms appeared during the Devonian period some 408 million years ago and were seed ferns. Gymnosperms have reached as high as 350 feet to as small as 4 inches in height. Worldwide there are 20 plant families with at least 50 percent of their species threatened. Of these, eight are gymnosperm families (including cycads and conifers). This may be due to the fact that many of their species are widely exploited for both timber and horticultural purposes, and, because they are an ancient group, they may not adapt easily to the rapidly changing environment around them. There are only 720 species compared with 250,000 species of angiosperms.

What is gynandromorphism ?

A female that develops partly or completely male characteristics. A lateral gynandromorph on one side has the external characters of the male, and the other side has those of the female. Common in bees and silkworms.