bluuebunny/crossref_metadata_2025 huggingface dataset:
Recombinational DNA Repair in Eukaryotes
Authors: Game John C
Published: September 2006

DNA double‐strand breaks and other damage can be repaired in cells by a process involving recombination with an undamaged homologous molecule. This is related to the recombination that occurs naturally during meiosis in most eukaryotes, and many of the same gene products are needed for both processes.
Homologous Genetic Recombination during Bacterial Conjugation
Authors: Rosenberg Susan M , Motamedi Mohammad R
Published: September 2006

Conjugation is the sexual transfer of deoxyribonucleic acid (DNA) from one bacterium directly into another. The transferred DNA can replace DNA of similar sequence in the recipient cell's chromosome by homologous genetic recombination, a process that both exchanges lengths of similar DNA sequences and repairs broken chromosomes, using similar chromosomes as templates.
Meiotic Recombination Pathways
Authors: Bishop Douglas K
Published: September 2006

Reciprocal recombination between homologous chromosomes in meiosis plays a critical role in promoting accurate reductional chromsome regulation. Meiotic recombination is highly regulated to ensure that at least one reciprocal crossover event occurs between each pair of homologous chromsomes.
RecA Protein
Authors: Bianco Piero R , Kowalczykowski Stephen C
Published: September 2006

The RecA protein of
Escherichia coli
is the prototypic DNA strand exchange protein. It assembles on single‐stranded DNA to form a helical nucleoprotein filament that is the active species for all RecA protein‐dependent functions. This protein–DNA complex is responsible for three mutually exclusive functions: DNA recombination, induction of the SOS response and SOS mutagenesis.
Rad51 and Eukaryotic Recombination Proteins
Authors: Ivanov Eugene L
Published: September 2006

Recombination proteins in eukaryotic cells function to provide genetic diversity and to maintain stability of the genome. They demonstrate high levels of structural and functional homology with each other and with those of prokaryotic organisms, suggesting that fundamental mechanisms of genetic recombination are conserved throughout the evolution.
Enzyme Activity: Reversible Inhibition
Authors: Morrison John F
Published: September 2006

Data for the inhibition of enzyme‐catalysed reactions by substrate analogues provide inhibition patterns that are helpful for the elucidation of kinetic mechanisms. Analysis of such data yields values for true inhibition constants that give a measure of the strength of interaction between the enzyme and the inhibitor.
Covalent Nucleophilic Catalysis
Authors: Kenyon George L
Published: September 2006

Covalent nucleophilic catalysis is the involvement of a nucleophile on an enzyme (usually one of the side‐chain groups of an α‐amino acid residue) in forming a covalent (shared) bond with a reactant to generate an intermediate on the reaction pathway leading to the observed product(s).
Transition States: Substrate‐induced Conformational Transitions
Authors: Post Carol B
Published: September 2006

Substrate binding produces a variety of conformational changes in an enzyme that result in favourable substrate–protein interactions and influence catalysis in different ways. The altered form of the enzyme often appears to be more active in catalysis. A specific conformational change that continues into the transition state complex is the basis for substrate specificity.
Lipoprotein Metabolism: Structure and Function
Authors: Brunzell John D , Chait Alan
Published: September 2006

Lipoproteins are particles in plasma which carry cholesterol and triglyceride. Lipoprotein metabolism is described based on structure and function of their apolipoproteins and the enzymes, transfer proteins and receptors involved in their assembly and catabolism. Genetic defects in lipoprotein metabolism highlight the functions of these metabolic parameters.
Oxidation–Reduction Reactions
Authors: McCormick Donald B
Published: September 2006

Oxidation–reduction reactions in nature are usually catalysed by enzymes classified broadly as oxidoreductases. These enhance the rate of electron transfer from an oxidizable substrate, typically a hydrogen donor, to a reducible acceptor.
Organic Reaction Mechanisms
Authors: le Noble William J
Published: September 2006

The mechanism of a reaction is a pathway by which the atoms travel from their initial positions in the reactants to the final ones in the products; of all the possible pathways, the one followed by most of the molecules in a sample is that which requires the smallest rise in free energy along the way. Reactions are called stepwise if they involve intermediate species with a finite lifetime, or concerted if they do not.
Binding Constants: Measurement and Biological Range
Authors: Winzor Donald J
Published: September 2006

Several methods exist for the measurement of binding constants for macromolecular interactions between dissimilar reactants. These allow biological interactions with binding constants in the range 102to 109 mol L−1to be characterized quantitatively.
Glycolysis Regulation
Authors: Lopaschuk Gary D
Published: September 2006

Glycolysis provides an important source of energy for most cells as well as a source of substrate for a number of other metabolic pathways. Its regulation is complex, involving allosteric control, phosphorylation control and transcriptional control of glycolytic enzymes. Modulation of fructose 2,6‐bisphosphate has emerged as one of the key sites at which glycolysis is controlled.
Transition State Stabilization
Authors: Mobashery Shahriar , Kotra Lakshmi P
Published: September 2006

The transition state is a high‐energy species occurring during the course of chemical reactions, the stabilization of which by either chemical reagents or enzymes enhances the rate of the given process.
Enzymatic Free Radical Reactions
Authors: Booker Squire J
Published: September 2006

Nature has evolved an array of cofactors to aid in the initiation of enzymatic reactions that take place via mechanisms involving unpaired electrons centred on carbon atoms. A unifying theme among many of these cofactors is that they contain metal atoms that participate intimately in the radical‐generation process.
Membrane Proteins
Authors: Reithmeier Reinhart AF
Published: September 2006

Biological membranes consist of lipids and proteins. The lipids
are arranged as a fluid bilayer and the proteins are either embedded in the
lipid or are bound to the membrane surface. Research on membranes has moved
from early studies of the lipids and membrane models to the determination of
the molecular structure of membrane proteins.
Nitrogen Fixation
Authors: Burris Robert H
Published: September 2006

Nitrogen fixation is the process by which nitrogen in the atmosphere is converted into a more active form that can be used by plants. Symbiotic biological nitrogen fixation occurs in leguminous and nonleguminous plants, and nitrogen is also fixed biologically by free‐living and associative nitrogen fixers.
Gluconeogenesis
Authors: Wallace John C , Barritt Greg J
Published: September 2006

The gluconeogenic pathway, which is found in the liver and kidney, involves the synthesis of glucose from three‐carbon precursors such as lactate, alanine and glycerol. The main function of gluconeogenesis is to supply glucose to tissues, such as brain and red blood cells, that depend on glucose as their main or sole energy source.
Amino Acid Biosynthesis
Authors: Deferrari Giacomo , Garibotto Giacomo
Published: September 2006

Amino acids are classically considered as the building blocks for the synthesis of proteins. Besides this, some of them play a major role in other functions, such as regulation of protein turnover and signal transduction, transport of nitrogen and carbon across the organs, or neurotransmission.
Binding and Catalysis
Authors: Toney Michael D
Published: September 2006

Binding and catalysis in the biological context are defined as the formation of a relatively long‐lived and specific complex between a macromolecular catalyst and a substrate molecule, which subsequently undergoes a chemical transformation much faster than would occur in the absence of the macromolecular catalyst.
Insulin and Glucagon
Authors: Brady Matthew J , Saltiel Alan R
Published: September 2006

Insulin and glucagon are reciprocal hormones which regulate plasma glucose concentrations. Together, these hormones maintain blood glucose in a narrow range, despite wide variances in glucose production and utilization by the body.
Starvation: Metabolic Changes
Authors: Brosnan John T , Watford Malcom
Published: September 2006

Animals, including humans, invoke a comprehensive programme of hormonal and metabolic adaptations that enable them to withstand prolonged periods of starvation. The main goal of such adaptations is to provide glucose for the brain and fat‐derived fuels for most of the other tissues of the body. This is achieved through a well orchestrated pattern of tissue‐specific fuel metabolism.
Lysosomal Degradation of Proteins
Authors: Dice J Fred
Published: September 2006

Lysosomal enzymes and lysosomal membrane proteins are targeted to lysosomes by distinct mechanisms. Mutations that cause a reduction in activity of a lysosomal enzyme cause a variety of lysosomal storage diseases. Lysosomes are able to take up and degrade proteins by at least five different pathways, and their contribution to overall proteolysis depends on the cell type and its physiological status.
Thiamin Diphosphate and Vitamin B
1
Authors: Schowen Susana K , Schowen K Barbara , Schowen Richard L
Published: September 2006

Thiamin diphosphate is the active form of thiamin (vitamin B
1
)
required as an enzyme cofactor to assist in fission and formation of
carbon–carbon bonds in biosynthetic and bioenergetic reactions.
Sodium, Calcium and Potassium Channels
Authors: Heinemann Stefan H
Published: September 2006

Sodium, calcium and potassium channels form the basis for the electrical excitability of various cell types. They are membrane proteins which harbour voltage‐gated pores providing selective permeation pathways for Na
+
, Ca
2+
and K
+
ions, respectively.
Water Channels
Authors: King Landon S , Agre Peter
Published: September 2006

Water can cross plasma membranes by diffusion through the lipid bilayer or by channel‐mediated water movement. Aquaporins are transmembrane proteins that are selectively permeable to water. These proteins are the first identified molecular water channels.
Myoglobin
Authors: Ishimori Koichiro
Published: September 2006

Myoglobin is an oxygen‐binding haem protein of vertebrate and
invertebrate skeletal and cardiac muscle.
Light‐harvesting Complex
Authors: Isaacs Neil W , Cogdell Richard J
Published: September 2006

Photosynthesis in purple photosynthetic bacteria takes place in a photosynthetic unit located in the cell membrane. Part of this unit is the light‐harvesting complex, an assembly of protein and pigment molecules.
Photosystem I
Authors: Krauß Norbert , Saenger Wolfram
Published: September 2006

In oxygenic photosynthesis, the two protein–pigment complexes photosystem I and photosystem II are involved in the light‐driven charge separation across the thylakoid membrane, which results in the oxidation of water to O
2
and in the reduction of NADP
+
to NADPH. In addition to a photosynthetic reaction centre, each of these photosystems contains a core antenna system. The crystal structure of photosystem I reveals the spatial organization of protein subunits and cofactors.
Coenzymes: Haem
Authors: Cheek Jennifer , Dawson John H
Published: September 2006

The tetrapyrrole porphyrin haem prosthetic group is found in a wide variety of proteins in almost all prokaryotic organisms. These proteins perform a diverse range of functions, including dioxygen binding, oxygen atom transfer, substrate oxidation and electron transport.
Iron Cofactors: Non‐haem
Authors: Fox Brian G
Published: September 2006

Proteins and enzymes with non‐haem iron centres display many functions: metal centres with primarily sulfur ligation are involved in electron transfer, electrophilic activation of hydroxyl groups, regulation of gene expression and fixation of N
2
; mononuclear and diiron centres with oxygen and nitrogen ligation have roles in various reactions with O
2
and in hydrolysis. The principles of their mechanisms of action are beginning to emerge from the considerable experimental data obtained on these proteins. Future research will attempt to manipulate the enzymes to extend their already substantial catalytic capabilities.
Motor Proteins
Authors: Cooke Roger
Published: September 2006

Motor proteins use chemical energy to produce force and movement in all living cells.
Radical Enzymes
Authors: Sjöberg Britt‐Marie , Sahlin Margareta
Published: September 2006

Radical enzymes are enzymes that harbour a stable free radical in their polypeptide chain or generate a transient free radical, that participates in catalysis. A growing number of enzymes are known to require a posttranslationally generated free radical for their proper functioning. The radical is generally used to remove a hydrogen atom from an unreactive position in the substrate, activating the substrate to undergo chemical transformations. Some radical enzymes have unexpectedly been found to harbour a stable radical on an amino acid side‐chain that is distinct from the side‐chains of the active site region; during catalysis the stable free radical interacts with the active site via electron or radical transfer and between turnovers it serves as a radical sink.
Myosin Superfamily
Authors: Kendrick‐Jones J , Hodge TP , Lister IMB , Roberts RC , Buss F
Published: September 2006

Myosins are a large family of actin‐based mechanoenzymes that bind and hydrolyse ATP to generate the force and movement along actin filaments necessary to drive a wide variety of cellular functions. Phylogenetic analysis has so far identified 17 distinct classes of myosin (designated I–XVII).
Peptide Chain Elongation: Models of the Elongation Cycle
Authors: Nierhaus Knud H
Published: September 2006

Three models of the ribosomal elongation cycle are used to explain the mechanism of protein synthesis on the ribosome. These are the allosteric three‐site model, the hybrid site model, and the α‐ε model. The α‐ε model reconciles most of the experimental data currently available.
Ubiquitin Pathway
Authors: Lam Y Amy , Pickart Cecile M
Published: September 2006

The conserved protein ubiquitin acts as a signal for degradation in a multienzyme, energy‐dependent proteolytic pathway.
Selenocysteine
Authors: Böck August
Published: September 2006

The trace element selenium is present in the form of selenocysteine in selected proteins of organisms from all three lines of descent. Selenocysteine incorporation is DNA encoded, determined by the UGA codon and occurs via a unique mechanism representing an expansion of the genetic code.
Monosaccharides
Authors: Ferrier Robin
Published: September 2006

Monosaccharides (sometimes imprecisely referred to as ‘sugars’) are the molecular ‘building blocks’ from which the carbohydrate family of natural products are constructed.
Plant Gums
Authors: BeMiller James N
Published: September 2006

The term gum is commonly applied to water‐soluble, nonstarch polysaccharides of commerce; such gums are present in both higher and lower plants. Plant gums and other gums are used in practical applications primarily to thicken or gel aqueous systems and to control water. They may also function as adhesives, crystallization inhibitors, emulsifying agents, emulsion stabilizers, encapsulating agents, film formers, foam stabilizers, suspending agents, suspension stabilizers, or syneresis inhibitors and/or impart other specific properties.
Glycolipids: Animal
Authors: Sen‐itiroh Hakomori , Ineo Ishizuka
Published: September 2006

Glycolipids are carbohydrates linked to lipid (either ceramide or glyceride). They are found in animal cells and tissues.
Lectins
Authors: Sharon Nathan , Lis Halina
Published: September 2006

Lectins are carbohydrate‐specific proteins that mediate cellular recognition and serve as tools in the study of glycoconjugates.
Enzyme Activity and Assays
Authors: Scopes Robert K
Published: September 2006

Enzyme activity refers to the general catalytic properties of an enzyme, and enzyme assays are standardized procedures for measuring the amounts of specific enzymes in a sample.
Triacylglycerols
Authors: Mann Jim , Skeaff Murray
Published: September 2006

Triacylglycerols are an important source of energy in the human diet, and when not immediately required for this purpose may be stored in the body in adipocytes.They are transported in thebloodstream as chylomicrons and very low‐density lipoproteins and stores are continually being broken down and resynthesized.
Enzyme Kinetics: Transient Phase
Authors: Johnson Kenneth A
Published: September 2006

Transient kinetic methods allow events occurring at the active site of an enzyme to be observed directly by monitoring reactions on a short time scale and with a sufficiently high concentration of enzyme to witness product formed in a single enzyme turnover. Rapid mixing methods provide unique kinetic information to define the reaction mechanism in terms that can be directly related to structure.
Metalloenzymes and Electrophilic Catalysis
Authors: Eames Jason , Watkinson Michael
Published: September 2006

Enzymes perform a number of remarkable synthetic transformations at neutral pH and ambient temperatures. Many enzymes employ metal ions to aid in electrophilic catalysis. Zinc, the commonest Lewis acid in biochemistry, is an essential cofactor in over 300 enzymes.
Glycerophospholipids
Authors: Farooqui Akhlaq A , Yeo Young K , Horrocks Lloyd A
Published: September 2006

Glycerophospholipids are derivatives of
sn‐
glycero‐3‐phosphoric acid. They contain an
O
‐acyl or
O
‐alkyl or
O
‐alk‐1′‐enyl residue at the
sn‐
1 position and an
O
‐acyl residue at the
sn‐
2 position of the glycerol moiety. Glycerophospholipid classes are defined on the basis of the substituents on the phosphoric acid at the
sn‐
3 position.
Vertebrate Embryo: Establishment of Left‐Right Asymmetry
Authors: Cooke Jonathan
Published: September 2006

All vertebrates have normally consistent left–right asymmetries of structure, and abnormalities of this asymmetry in humans are clinically important.
Vertebrate Embryo: Limb Development
Authors: Niswander Lee Ann
Published: September 2006

Limb development in the vertebrate embryo is an excellent model system for the study of embryonic growth and pattern formation. This process is mediated through a wide range of cellular and molecular signals.
XenopusEmbryo: β‐Catenin and Dorsal‐Ventral Axis Formation
Authors: Moon Randall T
Published: September 2006

During embryonic development of the amphibian,Xenopus laevis, the dorsal side of the embryo forms approximately opposite the sperm entry point, and the anterior and posterior axes are linked to this through the process of gastrulation. The mechanisms responsible for specification of the dorsal axis include a postfertilization cortical rotation that promotes a dorsal accumulation of β‐catenin, and the activation of a cascade of regulatory genes by the complexes of β‐catenin and HMG box transcription factors which starts the process of gastrulation.
XenopusEmbryo: Mesoderm Induction
Authors: Dale Leslie
Published: September 2006

Mesoderm induction has been most extensively studied in embryos of the frogXenopus laevis. These studies have demonstrated the key roles played by members of the TGF‐ß, FGF, and Wnt families of extracellular signalling molecules.
Zebrafish Embryo as a Developmental System
Authors: Amacher Sharon L
Published: September 2006

Zebrafish are simple, rapidly‐developing animals that are amenable to detailed developmental and genetic analyses. Despite their relatively simple morphology, they share many developmental features with other vertebrates. By combining developmental studies in zebrafish with those in other animals, we will begin to understand the complex events that occur as an embryo develops from a one‐celled zygote to a complex, multicellular organism.
Mammalian Embryo: Establishment of the Embryonic Axes
Authors: Beddington Rosa SP
Published: September 2006

In the mammalian embryo the establishment of the embryonic axes is not yet fully understood. At present, most is known about axis formation in the mouse.
Arabidopsis
: Flower Development and Patterning
Authors: Bowman John L
Published: September 2006

The development of flowers and floral organs is directed by genetic programmes likely to be universal amongst the angiosperms. A simple model explaining how a small number of regulatory genes acting alone and in combination to specify the identity of the floral organs (sepals, petals, stamens and carpels) is supported by both molecular and genetic experiments in
Arabidopsis
.
Vertebrate Embryo: Patterning the Neural Crest Lineage
Authors: Kalcheim Chaya
Published: September 2006

Neural crest cells form as epithelial progenitors during the process of neurulation, then undergo an epitheliomesenchymal transition and become motile. These mesenchymal cells migrate through stereotypical pathways, reach their homing sites, and differentiate into a large variety of neural and nonneural derivatives.
Mammalian Embryo: Hox Genes
Authors: Manzanares Miguel , Krumlauf Robb
Published: September 2006

Mammals have 39 Hox genes clustered in four complexes. This gene family controls transcription and is involved in patterning structures along the anterior–posterior axis of the embryo, including the nervous system, axial skeleton and limb bud.
Bacterial Flagella: Flagellar Motor
Authors: Berry Richard M
Published: September 2006

The bacterial flagellar motor is a rotary molecular motor situated in the cell envelopes of bacteria that is driven by a flow of charged ions across the bacterial plasma membrane. The motor powers the rotation of helical flagellar filaments so that bacteria swim, frequently towards a more favourable location.
Bromoviridaeand Allies
Authors: Scott Simon W
Published: September 2006

The familyBromoviridaeconsists of five genera:Alfamovirus,Bromovirus,Cucumovirus,IlarvirusandOleavirus. All viruses in these genera possess tripartite genomes of single‐stranded, linear, positive‐sense RNA, in which expression of the downstream codon of the RNA3 is via a subgenomic messenger RNA (RNA4).Raspberry bushy dwarf virus, the sole member of the genusIdaeovirus, shares features in common with members of the genusIlarvirusandAlfamovirusbut possesses a bipartite genome and has not been assigned to a family.
Caulimoviridae
(Plant Pararetroviruses)
Authors: Hull Roger
Published: September 2006

The
Caulimoviridae
family comprises six genera whose members replicate by reverse transcription hence the fact that they are also called pararetroviruses. The family
Caulimoviridae
is the only plant virus taxon whose members have double‐stranded DNA genomes.
Luteoviruses
Authors: Brault Véronique
Published: September 2006

Luteoviruses are plant viruses which can infect a wide range of host plants. They have icosahedral particles, are limited to the phloem tissue of the plant and are only transmitted by aphids.
Potexviruses and Carlaviruses ‐ Short Filamentous Viruses
Authors: Brunt Alan
Published: September 2006

Potexviruses and carlaviruses are plant‐infecting viruses; they have slightly flexuous filamentous particles containing 93–95% protein and 5–7% single‐stranded ribonucleic acid (RNA) and similar genomic organizations.
Tombusviridae
Authors: Giesman‐Cookmeyer Donna , Sit Tim L , Lommel Steven A
Published: September 2006

The family Tombusviridae is a relatively large and diverse family of viruses that have single‐stranded, positive‐sense, RNA genomes and that share morphological, structural, molecular and genetic features. It is a particularly well‐characterized family of viruses in the areas of virus structure, gene expression strategies, virus movement and the support of satellite viruses and defective‐interfering RNAs.
Plant Resistance to Infection with Viruses
Authors: Valkonen Jari P T
Published: September 2006

Infection of plants by viruses involves cycles of viral replication and cell‐to‐cell movement (for spread within the infected tissue), and viral long distance movement via the vascular tissue to different parts of the plant according to the source‐sink partitioning of photoassimilates. Plants defend themselves against viral infections by recognizing viral proteins with specific resistance genes, which induces the host defence mechanisms, or by destroying viral RNA using a cellular RNA surveillance mechanism (posttranscriptional gene silencing).
Virus Diseases of Cereals
Authors: Plumb Roger T
Published: September 2006

World food supply depends on cereals; wheat, maize, rice, barley, sorghum, oats, millet and rye provide much of the world's food and drink. Many different viruses cause diseases and yield loss on these crops.
Plant Virus Identification
Authors: Koenig Renate , Lesemann Dietrich‐Eckhardt
Published: September 2006

A reliable diagnosis is essential for the development of efficient stategies for the control of virus‐induced diseases. A large variety of identification procedures is available.
Plant Virus Satellites
Authors: Roossinck Marilyn J , Xu Ping
Published: September 2006

Plant virus satellites are molecular parasites of plant viruses that rely on a helper virus for replication but do not supply any essential function to the helper virus. They can alter the disease induced by the helper virus, often in the absence of any apparent protein products.
Bacteriophages
Authors: Maniloff Jack
Published: September 2006

Bacteriophages are viruses that infect bacteria. They are ubiquitous in the biosphere, and have evolved a wide range of morphologies and replication mechanisms to enable them to infect many kinds of eubacteria and archaebacteria.
Archaeal Viruses
Authors: Leisinger Thomas , Pfister Peter
Published: September 2006

Archaeal viruses are viruses that replicate in a host of the domain Archaea.
Bacteriophages in Industry
Authors: Callanan Michael J , Klaenhammer Todd R
Published: September 2006

The biotechnology industry has benefited from the molecular knowledge and tools derived from the study of bacteriophage biology. For industries that rely on bacteria for bioprocessing, fermentation failure due to phage infection is a long‐term and continuing problem.
Bacteriophages with ssRNA
Authors: van Duin Jan
Published: September 2006

The single‐stranded RNA (ssRNA) phages include about 100 isolates. The best‐characterized are those infecting
Escherichia coli
, a Gram‐negative bacterium found in the gut and faecal sewage. The genome of ssRNA phages assumes a highly optimized and unique structure that regulates translation of genes, confers RNAase resistance in the bacterial cytoplasm and ensures recognition by replicase.
Bacteriophages: Lipid‐containing
Authors: Bamford Dennis H
Published: September 2006

Bacteriophages, viruses that infect bacteria, are a large, varied group of viruses. Some of them have lipid constituents in addition to nucleic acid and protein. This has implications in particular for cell entry processes.
Bacteriophages: Tailed
Authors: Ackermann Hans‐W
Published: September 2006

Tailed bacteriophages constitute the order
Caudovirales
with three families. They are the largest and probably oldest virus group and are extremely diversified in dimensions and physicochemical properties, but have retained many common properties in morphology and replication.
Bacteriophage Lambda and its Relatives
Authors: Casjens Sherwood R , Hendrix Roger W
Published: September 2006

Bacteriophage lambda is a virus that infects the bacterial species
Escherichia coli
. It is a temperate virus, in that it can either make virion progeny in its host, or establish a state in which its chromosome is integrated into the host chromosome and its own replicative genes are turned off.
Bacteriophage T4
Authors: Mathews Christopher K
Published: September 2006

Analysis of molecular events following infection of

Escherichia coli

by
bacteriophage T4
has revealed some of the most fundamental principles of biology, including the chemical nature of genes and mechanisms of gene expression. In addition, the phage has provided researchers with virus‐coded proteins that are continuing to serve as reagents to help fuel the biological revolution that began in 1953 with Watson and Crick and is continuing today.
Ear and Lateral Line of Vertebrates: Organization and Development
Authors: Fritzsch Bernd
Published: September 2006

The mechanoelectrical transducers of vertebrates (the hair cells) form the basis for two distinct sensory systems: the lateral line and the inner ear. These two sensory systems share other features such as development and central projections and are therefore grouped together as the octavolateral system.
Caenorhabditis elegans
Neural Development
Authors: Brockie Penelope J , Maricq Andres V
Published: September 2006

The nervous system of the nematode
Caenorhabditis elegans
has been well described in terms of cell lineage, neural anatomy and connectivity. Identifying mutations that disrupt these defining characteristics has led to a detailed understanding of the genetic and molecular mechanisms of neural development in
C. elegans
.
Axon Guidance
Authors: Keynes Roger J , Cook Geoffrey MW
Published: September 2006

Axon guidance is the means whereby axon processes growing from differentiating nerve cells are guided to their targets during embryonic development.
Developmental Biology of Synapse Formation
Authors: Montanaro Federica , Carbonetto Salvatore
Published: September 2006

Synapses are specialized sites for communication between neurons and their targets involved in the processing of information and the generation of behaviour and thought. The formation of synapses during development and their remodelling involves a complex bidirectional signalling between the neuron and its target.
Neural Tube Defects
Authors: Copp Andrew J
Published: September 2006

Neural tube defects (NTDs) are congenital malformations of the central nervous system and axial skeleton that range from the fatal to the asymptomatic. NTDs can be classified according to the embryonic event that is disturbed, and may result from a variety of genetic defects and environmental influences. Understanding the genetic and embryonic basis of NTDs is enabling new approaches towards prevention of these serious birth defects, a strategy exemplified by the ability of folic acid and other vitamins to prevent spina bifida.
BMP Antagonists and Neural Induction
Authors: Eggen Bart JL , Hemmati‐Brivanlou Ali
Published: September 2006

In vertebrates, during the gastrula stage of embryonic development, the dorsal part of the ectoderm (the animal pole) is fated to form the neural plate, whereas the ectoderm located at the ventral side will primarily form epidermis. Embryonic factors known as BMP antagonists play a critical role in the processes of neural and epidermal induction.
Hedgehog Signalling
Authors: Capdevila Javier
Published: September 2006

Hedgehog genes encode a family of secreted proteins that control the development of many organs and structures in vertebrates and invertebrates.
Nucleic Acids as Genetic Material
Authors: Judd Burke H
Published: September 2006

Nucleic acids are long linear or circular macromolecules, either DNA or various types of RNA, that are composed of linked nucleotides. These molecules carry genetic information that directs all cellular functions.
Genetic Code: Introduction
Authors: Watanabe Kimitsuna
Published: September 2006

The genetic code establishes the relationship between all 64 possible arrangements of the four nucleotide bases contained in either DNA (A, T, G and C) or RNA (A, U, G and C) and the 20 amino acids that are used to construct proteins. The historical events that contributed to the deciphering of the genetic code led to the development of the field of molecular biology.
Genetic Code and its Variants
Authors: Watanabe Kimitsuna , Suzuki Tsutomu
Published: September 2006

The universal genetic code is a common language for almost all organisms to translate nucleotide sequences of DNA and RNA to amino acid sequences of proteins. Some organisms and organelles use variants of the universal genetic code.
Experimental Organisms Used in Genetics
Authors: Judd Burke H
Published: September 2006

Most model genetic systems share important characteristics that make them amenable to growth and analysis in the laboratory. These include genetic mapping by recombination, tests for dominance and complementation. Development of a system for transformation and obtaining the complete nucleotide sequence of the genome are also very important.
Linkage and Crossing over
Authors: Kohli Jürg
Published: September 2006

Genetic mapping of genes in eukaryotes is based on the mechanisms leading to new combinations of genes: random assortment of chromosomes and crossing‐over.
Gene Conversion
Authors: Hurles Matthew E
Published: September 2006

Gene conversion is the nonreciprocal transfer of information between homologous sequences and is closely associated with meiotic recombination and the mismatch repair of DNA heteroduplex.
Yeast as a Model Genetic Organism
Authors: Mell Joshua Chang , Burgess Sean M
Published: September 2006

The budding yeast is an ideal experimental organism for genetic research. The yeast shares a common life cycle and cellular architecture with higher eukaryotes, and as a microorganism it is easily propagated and manipulated in the laboratory.
Neurogenesis in
Drosophila
Authors: Dambly‐Chaudière Christine , Ghysen Alain
Published: September 2006

The diversity of neural cell types in
Drosophila
is generated by genetic modulations of reiterated processes.
Axon Guidance at the Midline
Authors: Tear Guy , Georgiou Marios
Published: September 2006

Much has been learnt about how axons are guided along their appropriate paths by studying axon growth at the midline of the central nervous system in a number of model systems. The specialized midline cells produce both attractive and repellent short‐ and long‐range signals and the axons express specific receptors that are dynamically regulated. It has become clear from these studies that the molecular mechanisms used to guide axons have been highly conserved during evolution.
Ephrins
Authors: Klein Rüdiger
Published: September 2006

Ephrins are cell surface‐associated or transmembrane proteins which can bind via their extracellular domain members of the Eph receptor tyrosine kinases. Ephrin–Eph interactions can trigger a variety of responses, including axon and cellular guidance and patterning of brain structures.
Photoreceptor Cell Development Control
Authors: Zhang Xin , Maas Richard L
Published: September 2006

Photoreceptor development is directed by both extrinsic signals and intrinsic factors. The mechanism of regulation is now studied in molecular detail.
Motor Control Network Development
Authors: Sillar Keith Thomas
Published: September 2006

Reviewed knowledge on the development of motor networks in the vertebrate spinal chord and brainstem that control rhythmic locomotory movements.
Microsatellite Instability
Authors: Schlötterer Christian , Harr Bettina
Published: September 2006

Microsatellites are a ubiquitous component of the genome of higher organisms. Their high mutation rate provides the basis for the successful use of microsatellites as genetic markers. Exceptionally long microsatellites have been found to be associated with certain human genetic diseases.
Transposons as Natural and Experimental Mutagens
Authors: Woodruff RC , Thompson James N
Published: September 2006

Transposons are sequences of deoxyribonucleic acid (DNA) that have the ability to move from one genome location to another causing deleterious mutations and chromosome rearrangements. These elements, which are under self‐regulation and regulation by their hosts, are used as vectors to move foreign DNA into transgenic plants and animals and as experimental mutagens to tag genes. Transposons are also occasionally used in adaptive ways by the host in spite of their short‐term deleterious effects on fitness.
Repression Mechanism
Authors: Adhya Sankar
Published: September 2006

Repressors are regulator proteins that inhibit transcription initiation at gene promoters in order to modulate gene expression in response to variations in environmental conditions. The molecular and biochemical mechanisms by which such repression is achieved vary widely, and are often modulated by signal molecules which act by altering their mechanism of action.
Sigma Factors in Gene Expression
Authors: Helmann John D
Published: September 2006

Sigma factors control the promoter selectivity of bacterial RNA polymerase. The synthesis of new sigma factors allows the coordinated activation of discrete sets of genes and thereby contributes to stress responses, motility, endospore formation, and numerous other adaptive responses.
Regulatory Systems: Two‐component
Authors: Raivio Tracy L , Silhavy Thomas
Published: September 2006

Two‐component systems constitute a large class of regulatory proteins that function as signal transducers. Each system is comprised of a sensor or histidine kinase and an effector or response regulator, which communicate through a conserved set of phosphotransfer reactions to effect adaptive changes in response to specific environmental signals.
Translation Control by
RNA
Authors: Goldman Emanuel
Published: September 2006

Translation control by RNA refers to the process by which protein synthesis is regulated by structural elements in RNA (primary, secondary or tertiary), usually
cis
‐acting in the messenger RNA encoding the protein being synthesized, but also
trans
‐acting in some systems.
Enzyme Activity: Control
Authors: Yohrling IV George J , Jiang George C‐T , Vrana Kent E
Published: September 2006

Enzymes are the metabolic catalysts that effect a multitude of physiological processes and responses. Tight control of enzyme activity is therefore essential in maintaining the steady state of all organisms.
Catalytic
RNA
Authors: Walter Frank , Westhof Eric
Published: September 2006

Some RNA molecules can function like enzymes and exert a catalytic action on themselves or on other molecules. These ribozymes are diverse in size and sequence and differ in important aspects of their three‐dimensional structure and folding. Catalytic RNAs present a new target for drugs and can be used for inactivating unwanted RNA or DNA molecules by a specific cleavage reaction.
Engineered Enzymes
Authors: Dunn Ben M
Published: September 2006

The term ‘engineered enzymes’ encompasses the process of creating new proteins through manipulation of the DNA of the gene encoding the protein. The engineered gene is translated into protein through expression in a suitable cellular system.
Cellular
RNA
s: Varied Roles
Authors: Gu Jian , Reddy Ram
Published: September 2006

In the cell, there are three major types of RNA directly involved in protein synthesis. In addition, many other cellular RNAs also play important functions.
Messenger
RNA
in Prokaryotes
Authors: Kushner Sidney R
Published: September 2006

Messenger RNAs (mRNAs) are molecules that represent the intermediate step in converting the genetic information carried in a cell's DNA to functional proteins. Structural features of mRNAs control both how effectively their contained data are translated into functional proteins and how rapidly they are destroyed.
Messenger
RNA
: Interaction with Ribosomes
Authors: Carr‐Schmid Anne , Kinzy Terri Goss
Published: September 2006

The recruitment and binding of a messenger RNA (mRNA) to the ribosome is a highly specific and regulated process. This process depends on unique sequences and structures within the mRNA, soluble auxiliary factors as well as the RNA and protein components of the ribosome to allow the synthesis of proteins.
Ribosomal RNA
Authors: Lafontaine Denis LJ , Tollervey David
Published: September 2006

All proteins are synthesized by ribosomes, large RNA–protein complexes that function as ribozymes and are the targets of several clinically relevant antibiotics. Ribosomes contain highly conserved rRNA species, which catalyse the key steps in protein synthesis, together with 70–80 proteins that play important roles in the correct folding and packaging of the rRNAs.
m
RNA
Splicing: Role of
sn
RNA
s
Authors: Padgett Richard A
Published: September 2006

Many small nuclear ribonucleic acids (snRNAs) of eukaryotic cells are involved in the maturation of primary transcripts of messenger RNAs (mRNAs). Certain snRNAs are involved in the formation and function of the spliceosome, a large ribonucleoprotein structure in which pre‐mRNA splicing takes place.
Intron Homing
Authors: Edgell David R , Landthaler Markus , Shub David A
Published: September 2006

Introns belonging to the group I or group II self‐splicing types are mobile elements that can move into unoccupied sites in homologous genes (homing), or into new genomic sites (transposition). This mobility is mediated by intron‐encoded proteins: site‐specific endonucleases in the case of group I introns and chimaeric proteins containing reverse transcriptase activity for group II introns.
Introns: Group I Structure and Function
Authors: Paquin Bruno , Shub David A
Published: September 2006

Group I introns fold into characteristic secondary and tertiary structures. In a Mg
2+
‐dependent reaction initiated by a guanosine cofactor, group I ribozymes catalyse their own excision from the primary transcript. In addition, group I introns often contain an open reading frame that assists the intron in its own mobility.
Protein‐coding Segments: Evolution of Exon‐Intron Gene Structure
Authors: Long Manyuan
Published: September 2006

Many genes are disrupted by noncoding regions of DNA of variable sizes called introns, giving the genes an exon–intron structure. Most introns, particularly spliceosomal introns found in the nuclei of higher eukaryotes, have no obvious functions.
Messenger
RNA
Splicing Signals
Authors: Mount Stephen M
Published: September 2006

Splicing signals are elements in the DNA sequence of a gene that specify the accurate splicing of its primary RNA transcript to generate its mature RNA product.
RNA Editing
Authors: Sowden Mark P , Smith Harold C
Published: September 2006

RNA editing is a form of RNA processing that can occur in either the nucleus, chloroplast or mitochondrion of cells and involves the co‐ or posttranscriptional modification of RNA from that encoded in DNA through nucleotide deletion, insertion or base‐modification mechanisms.
RNA
Intracellular Transport
Authors: Palacios Isabel , Izaurralde Elisa
Published: September 2006

RNA intracellular transport includes the export of an RNA from its site of synthesis, the nucleus, to the cytoplasm and for some RNAs, the subsequent localization to specific cytoplasmic subdomains.
mRNA Splicing: Regulated and Differential
Authors: Cooper Thomas A
Published: September 2006

Alternative splicing is the process by which single genes express multiple messenger RNAs (mRNAs), and therefore multiple proteins, by differential processing of the primary transcript (pre‐mRNA). The temporal and spatial regulation of protein expression by alternative splicing is determinative for such diverse biological processes as gender specification inDrosophila, commitment to apoptosis, and sound frequency recognition of individual hair cells in the avian cochlea.
Spleen
Authors: Steiniger Birte
Published: September 2006

The spleen is a secondary lymphoid organ present in all vertebrates. It is structurally complex and has a number of different functions for the purpose of maintaining normal homeostasis, such as destroying old red blood cells and storing blood.
Mucosal Lymphoid Tissues
Authors: Lycke Nils Y
Published: September 2006

The mucosal membranes host the largest component of the immune system and most of our lymphocytes are found there. These tissues are important for host defence against invasive microorganisms and also function as barriers that allow nutrients to be taken up while preventing unwanted substances from entering further into the body.
Antibody Classes
Authors: Wingren Christer , Alkner Ulf , Hansson Ulla‐Britt
Published: September 2006

Antibodies are glycoproteins belonging to the immunoglobulin family. The immunoglobulins have a common four‐chain structure (two identical light chains and two identical heavy chains) and they can be divided into different classes (and subclasses) according to the isotype of the heavy chain. The heavy‐chain isotype will confer different structural and functional properties on each antibody class, so that each isotype will occupy a specific site in the body and have a specific role to play in the immune system.
Secondary Metabolites: Attracting Pollinators
Authors: Harborne Jeffrey B
Published: September 2006

When insects, bats, birds and other animals visit flowers to feed on the nectar and pollen, they usually pollinate the flowers in the process, so that both partners benefit from this mutualistic association. Secondary metabolites are involved primarily to provide either visual or olfactory attraction in terms of flower colour and flower scent. They may also be present in the nectar and pollen to interact with certain visitors.
Plant Volatiles
Authors: Vaughn Steven F
Published: September 2006

Plant volatiles are chemicals responsible for their characteristic odours, and have important ecological functions for the plants in attracting pollinators, assisting in seed dissemination, and in resisting attack by predators and pathogens. Plant volatiles are also utilized extensively by humans as perfumes and flavourings.
Fc Receptors
Authors: Van Vugt Martine J , Van de Winkel Jan GJ
Published: September 2006

Receptors for the Fc region of immunoglobulins link humoral responses to cellular activities within the immune system. Leucocyte Fc receptors exist as hetero‐oligomeric complexes with unique ligand‐binding α chains and promiscuous accessory subunits.
Secondary Metabolites: Deterring Herbivores
Authors: Wink Michael
Published: September 2006

Secondary metabolites that can interfere with basic molecular targets of animals or microbes provide plants with protection against herbivores and/or microbes, since plants cannot run away when attacked by herbivores and do not have an immune system to defend themselves against microbes.
Major Histocompatibility Complex (MHC)
Authors: Penn Dustin J
Published: September 2006

The major histocompatibility complex (MHC) contains the most diverse genes known in vertebrates, the class I and II loci. These highly polymorphic genes encode cell surface receptors that play a central role in controlling immunological self/nonself recognition, and subsequently tissue rejection, autoimmunity, and immune responses to infectious diseases. The polymorphisms of MHC genes has been maintained by natural selection over long periods of evolutionary time.
Major Histocompatibility Complex: Human
Authors: Penn Dustin J
Published: September 2006

The major histocompatibility complex (MHC) is a large genetic region that contains the most polymorphic loci known in humans and other vertebrates. MHC genes are the most intensively studied genes because they influence so many important traits, including resistance to infectious diseases, autoimmunity, compatibility of tissue transplants, spontaneous abortion, odour and mating preferences.
Major Histocompatibility Complex (MHC): Mouse
Authors: Melvold Roger W
Published: September 2006

The major histocompatibility complex (MHC) of the mouse, the
H2
(or
Histocompatibility‐2
; formerly abbreviated as
H‐2
) complex, is located on chromosome 17. It contains genes critical to the functioning of the immune system because their products are intimately involved in the earliest steps in initiating immune responses. There is great variation among these genes, a trait that is unusual and probably critical to the immune system.
Major Histocompatibility Complex: Interaction with Peptides
Authors: Achour Adnane
Published: September 2006

MHC molecules are proteins expressed on the cell surface whose main function is to present a diversity of peptides to cells of the immune system. The quality of the MHC–peptide interaction will ultimately decide the nature of the immune response elicited.