Bebenhausen
Bebenhausen is a village in the Tübingen district, Baden-Württemberg, Germany. Since 1974 it is a district of the city of Tübingen and it is located 3 km north of Tübingen proper, in the southeastern part of the protected landscape of the Schönbuch, a dense forest. Bebenhausen is famous for its monastery, Bebenhausen Abbey, founded in 1183 by Count Palatine Rudolph of Tübingen, early 19th century the monastery became a hunting palace for the kings of Württemberg. King William II of Württemberg lived there until his death in 1921 and it became the seat of Württemberg-Hohenzollern from 1947 and until 1952 when Baden-Württemberg was created. In 1974, Bebenhausen became a district of Tübingen
Developmental biology
Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology encompasses the biology of regeneration, asexual reproduction and metamorphosis and in the growth, regional specification refers to the processes that create spatial pattern in a ball or sheet of initially similar cells. This generally involves the action of cytoplasmic determinants, located within parts of the fertilized egg, the early stages of regional specification do not generate functional differentiated cells, but cell populations committed to develop to a specific region or part of the organism. These are defined by the expression of combinations of transcription factors. Morphogenesis relates to the formation of three-dimensional shape and it mainly involves the orchestrated movements of cell sheets and of individual cells. Morphogenesis is important for creating the three layers of the early embryo and for building up complex structures during organ development. Cell differentiation relates specifically to the formation of cell types such as nerve, muscle.
Differentiated cells contain large amounts of proteins associated with the cell function. Growth involves both an increase in size, and the differential growth of parts which contributes to morphogenesis. Growth mostly occurs through cell division but changes of cell size. The control of timing of events and the integration of the processes with one another is the least well understood area of the subject. It remains unclear whether animal embryos contain a master clock mechanism or not, the development of plants involves similar processes to that of animals. However plant cells are mostly immotile so morphogenesis is achieved by differential growth, the inductive signals and the genes involved in plant development are different from those that control animal development. Cell differentiation is the process whereby different functional cell types arise in development, for example, muscle fibers and hepatocytes are well known types of differentiated cell. The genes encoding these proteins are highly active, for example, NeuroD is a key transcription factor for neuronal differentiation, myogenin for muscle differentiation, and HNF4 for hepatocyte differentiation.
Cell differentiation is usually the final stage of development, preceded by several states of commitment which are not visibly differentiated, a single tissue, formed from a single type of progenitor cell or stem cell, often consists of several differentiated cell types. Control of their formation involves a process of inhibition, based on the properties of the Notch signaling pathway. For example, in the plate of the embryo this system operates to generate a population of neuronal precursor cells in which NeuroD is highly expressed
Transcription factor
In molecular biology, a transcription factor is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. In turn, this helps to regulate the expression of genes near that sequence, transcription factors work alone or with other proteins in a complex, by promoting, or blocking the recruitment of RNA polymerase to specific genes. A defining feature of transcription factors is that they contain at least one DNA-binding domain, transcription factors are usually classified into different families based on their DBDs. Transcription factors are essential for the regulation of expression and are, as a consequence. The number of factors found within an organism increases with genome size. Therefore, approximately 10% of genes in the code for transcription factors. Hence, the use of a subset of the approximately 2000 human transcription factors easily accounts for the unique regulation of each gene in the human genome during development.
Transcription factors bind to either enhancer or promoter regions of DNA adjacent to the genes that they regulate, depending on the transcription factor, the transcription of the adjacent gene is either up- or down-regulated. Transcription factors use a variety of mechanisms for the regulation of gene expression and these mechanisms include, stabilize or block the binding of RNA polymerase to DNA catalyze the acetylation or deacetylation of histone proteins. The transcription factor can either do this directly or recruit other proteins with this catalytic activity and they bind to the DNA and help initiate a program of increased or decreased gene transcription. As such, they are vital for important cellular processes. Many of these GTFs do not actually bind DNA, but rather are part of the large transcription preinitiation complex that interacts with RNA polymerase directly, the most common GTFs are TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH. The preinitiation complex binds to regions of DNA upstream to the gene that they regulate.
Other transcription factors regulate the expression of various genes by binding to enhancer regions of DNA adjacent to regulated genes. These transcription factors are critical to making sure that genes are expressed in the cell at the right time and in the right amount. Many transcription factors in multicellular organisms are involved in development, the Hox transcription factor family, for example, is important for proper body pattern formation in organisms as diverse as fruit flies to humans. Another example is the transcription factor encoded by the Sex-determining Region Y gene, cells can communicate with each other by releasing molecules that produce signaling cascades within another receptive cell. If the signal requires upregulation or downregulation of genes in the recipient cell, the estrogen receptor goes to the cells nucleus and binds to its DNA-binding sites, changing the transcriptional regulation of the associated genes
Embryology
Embryology is the branch of biology that studies the prenatal development of gametes and development of embryos and fetuses. Additionally, embryology encompasses the study of disorders that occur before birth. After cleavage, the cells, or morula, becomes a hollow ball, or blastula. In bilateral animals, the blastula develops in one of two ways that divides the whole animal kingdom into two halves. If in the blastula the first pore becomes the mouth of the animal, it is a protostome, the protostomes include most invertebrate animals, such as insects and molluscs, while the deuterostomes include the vertebrates. In due course, the changes into a more differentiated structure called the gastrula. The middle layer, or mesoderm, gives rise to the muscles, skeleton if any, the outer layer of cells, or ectoderm, gives rise to the nervous system, including the brain, and skin or carapace and hair, bristles, or scales. Embryos in many species appear similar to one another in early developmental stages.
The reason for this similarity is because species have an evolutionary history. These similarities among species are called homologous structures, which are structures that have the same or similar function and mechanism, Drosophila melanogaster, a fruit fly, is a model organism in biology on which much research into embryology has been done. Before fertilization, the female produces an abundance of mRNA - transcribed from the genes that encode bicoid protein. These mRNA molecules are stored to be used in what become the developing embryo. The male and female Drosophila gametes exhibit anisogamy, the female gamete is larger than the male gamete because it harbors more cytoplasm and, within the cytoplasm, the female gamete contains an abundance of the mRNA previously mentioned. At fertilization, the male and female gametes fuse and the nucleus of the male gamete fuses with the nucleus of the female gamete, note that before the gametes nuclei fuse, they are known as pronuclei. A series of nuclear divisions will occur without cytokinesis in the zygote to form a cell known as a syncytium.
All the nuclei in the syncytium are identical, just as all the nuclei in every cell of any multicellular organism are identical in terms of the DNA sequence of the genome. Before the nuclei can differentiate in transcriptional activity, the embryo must be divided into segments, in each segment, a unique set of regulatory proteins will cause specific genes in the nuclei to be transcribed. The resulting combination of proteins will transform clusters of cells into early embryo tissues that will develop into multiple fetal
Magdeburg
Magdeburg is the capital city and the second largest city of the state of Saxony-Anhalt, Germany. Magdeburg is situated on the Elbe River and was one of the most important medieval cities of Europe, Emperor Otto I, the first Holy Roman Emperor, founder of the archbishopric of Magdeburg, was buried in the towns cathedral after his death. Magdeburgs version of German town law, known as Magdeburg rights, spread throughout Central, the city is well known for the 1631 Sack of Magdeburg, which hardened Protestant resistance during the Thirty Years War. Prior to it Magdeburg was one of the largest German cities, Magdeburg was destroyed twice in its history. Magdeburg is the site of two universities, the Otto-von-Guericke University and the Magdeburg-Stendal University of Applied Sciences, nowadays Magdeburg is a traffic junction as well as an industrial and trading centre. In 2005 Magdeburg celebrated its 1200th anniversary, in June 2013 Magdeburg was hit by record breaking flooding. Founded by Charlemagne in 805 as Magadoburg, the town was fortified in 919 by King Henry I the Fowler against the Magyars and Slavs.
Edith loved the town and often lived there, at her death she was buried in the crypt of the Benedictine abbey of Saint Maurice, in 937, Magdeburg was the seat of a royal assembly. Otto I repeatedly visited Magdeburg and was buried in the cathedral. He granted the abbey the right to income from various tithes, the Archbishopric of Magdeburg was founded in 968 at the synod of Ravenna, Adalbert of Magdeburg was consecrated as its first archbishop. The archbishopric under Adalbert included the bishoprics of Havelberg, Merseburg, the archbishops played a prominent role in the German colonisation of the Slavic lands east of the Elbe river. In 1035 Magdeburg received a patent giving the city the right to hold exhibitions and conventions. These laws were adopted and modified throughout Central and Eastern Europe, visitors from many countries began to trade with Magdeburg. In the 13th century, Magdeburg became a member of the Hanseatic League, with more than 20,000 inhabitants Magdeburg was one of the largest cities in the Holy Roman Empire.
The town had a maritime commerce on the west, with the countries of the North Sea. The citizens constantly struggled against the archbishop, becoming independent from him by the end of the 15th century. In about Easter 1497, the twelve-year-old Martin Luther attended school in Magdeburg, in 1524, he was called to Magdeburg, where he preached and caused the citys defection from Catholicism. The Protestant Reformation had quickly found adherents in the city, where Luther had been a schoolboy, Emperor Charles V repeatedly outlawed the unruly town, which had joined the Alliance of Torgau and the Schmalkaldic League
Drosophila melanogaster
Drosophila melanogaster is a species of fly in the family Drosophilidae. The species is generally as the common fruit fly or vinegar fly. It is typically used because it is a species that is easy to care for, has four pairs of chromosomes, breeds quickly. D. melanogaster is a common pest in homes, flies belonging to the family Tephritidae are called fruit flies. This can cause confusion, especially in Australia and South Africa, the D. melanogaster lifespan is about 30 days at 29 °C. The developmental period for D. melanogaster varies with temperature, as with many ectothermic species, the shortest development time,7 days, is achieved at 28 °C. Development times increase at higher temperatures due to heat stress, under ideal conditions, the development time at 25 °C is 8.5 days, at 18 °C it takes 19 days and at 12 °C it takes over 50 days. Under crowded conditions, development time increases, while the emerging flies are smaller, females lay some 400 eggs, about five at a time, into rotting fruit or other suitable material such as decaying mushrooms and sap fluxes.
The eggs, which are about 0.5 mm long, the resulting larvae grow for about 4 days while molting twice, at about 24 and 48 h after hatching. During this time, they feed on the microorganisms that decompose the fruit, the mother puts feces on the egg sacs to establish the same microbial composition in the larvaes guts which has worked positively for herself. Then the larvae encapsulate in the puparium and undergo a four-day-long metamorphosis, the female fruit fly prefers a shorter duration when it comes to sex. Males, on the hand, prefer it to last longer. Males perform a sequence of five behavioral patterns to court females, males orient themselves while playing a courtship song by horizontally extending and vibrating their wings. Soon after, the positions itself at the rear of the females abdomen in a low posture to tap. Finally, the male curls its abdomen and attempts copulation, females can reject males by moving away and extruding their ovipositor. Copulation lasts around 15–20 minutes, during which males transfer a few hundred, females store the sperm in a tubular receptacle and in two mushroom-shaped spermathecae, sperm from multiple matings compete for fertilization. A last male precedence is believed to exist in which the last male to mate with a female sires about 80% of her offspring and this precedence was found to occur through both displacement and incapacitation.
The displacement is attributed to sperm handling by the fly as multiple matings are conducted and is most significant during the first 1–2 days after copulation
RNA polymerase
RNA polymerase, known as DNA-dependent RNA polymerase, is an enzyme that produces primary transcript RNA. In cells, RNAP is necessary for constructing RNA chains using DNA genes as templates, RNA polymerase enzymes are essential to life and are found in all organisms and many viruses. In chemical terms, RNAP is a transferase that polymerizes ribonucleotides at the 3 end of an RNA transcript. RNAP was discovered independently by Charles Loe, Audrey Stevens, the 2006 Nobel Prize in Chemistry was awarded to Roger D. Kornberg for creating detailed molecular images of RNA polymerase during various stages of the transcription process. Therefore, it is surprising that the activity of RNAP is long, complex. In Escherichia coli bacteria, more than 100 transcription factors have been identified, RNAP can initiate transcription at specific DNA sequences known as promoters. It produces an RNA chain, which is complementary to the template DNA strand, the process of adding nucleotides to the RNA strand is known as elongation, in eukaryotes, RNAP can build chains as long as 2.4 million nucleotides.
RNAP will preferentially release its RNA transcript at specific DNA sequences encoded at the end of genes, products of RNAP include, Messenger RNA —template for the synthesis of proteins by ribosomes. Non-coding RNA or RNA genes—a broad class of genes that encode RNA that is not translated into protein, the most prominent examples of RNA genes are transfer RNA and ribosomal RNA, both of which are involved in the process of translation. However, since the late 1990s, many new RNA genes have been found and it is able to do this because specific interactions with the initiating nucleotide hold RNAP rigidly in place, facilitating chemical attack on the incoming nucleotide. Such specific interactions explain why RNAP prefers to start transcripts with ATP, in contrast to DNA polymerase, RNAP includes helicase activity, therefore no separate enzyme is needed to unwind DNA. There are multiple interchangeable sigma factors, each of which recognizes a set of promoters. After binding to the DNA, the RNA polymerase switches from a complex to an open complex.
This change involves the separation of the DNA strands to form a section of DNA of approximately 13 bp. Ribonucleotides are base-paired to the template DNA strand, according to Watson-Crick base-pairing interactions, supercoiling plays an important part in polymerase activity because of the unwinding and rewinding of DNA. Because regions of DNA in front of RNAP are unwound, there are compensatory positive supercoils, regions behind RNAP are rewound and negative supercoils are present. As noted above, RNA polymerase makes contacts with the promoter region, however these stabilizing contacts inhibit the enzymes ability to access DNA further downstream and thus the synthesis of the full-length product. Once the open complex is stabilized, RNA polymerase synthesizes an RNA strand to establish a DNA-RNA heteroduplex at the active center, which stabilizes the elongation complex
Edward B. Lewis
Edward Butts Lewis was an American geneticist, a corecipient of the 1995 Nobel Prize in Physiology or Medicine. Lewis was born in Wilkes-Barre, the son of Laura Mary Lewis and Edward Butts Lewis. His full name was supposed to be Edward Butts Lewis Jr. Lewis graduated from E. L. Meyers High School. He received a BA in Biostatistics from the University of Minnesota in 1939, in 1942 Lewis received a Ph. D. from California Institute of Technology, working under the guidance of Alfred Sturtevant. After serving as a meteorologist in the U. S. Air Force in World War II, in 1956 he was appointed Professor of Biology, and in 1966 the Thomas Hunt Morgan Professor of Biology. He is credited with development of the complementation test and his key publications in the fields of genetics, developmental biology and cancer are presented in the book Genes and Cancer, which was released in 2004. During the 1950s, Lewis studied the effects of radiation from X-rays, nuclear fallout and he reviewed medical records from survivors of the atomic bombings of Hiroshima and Nagasaki, as well as radiologists and patients exposed to X-rays.
Lewis concluded that health risks from radiation had been underestimated, Lewis published articles in Science and other journals and made a presentation to a Congressional committee on atomic energy in 1957. On November 20,2001 Lewis was interviewed by Elliot Meyerowitz in the Kerckhoff Library at the California Institute of Technology and this interview was released on DVD in 2004 as Conversations in Genetics, Volume 1, No.3 - Edward B. Lewis, An Oral History of Our Intellectual Heritage in Genetics 67 min, Producer Rochelle Easton Esposito and he was elected a Foreign Member of the Royal Society in 1989. He was awarded the Gairdner Foundation International award in 1987, the Wolf Foundation prize in medicine in 1989, the Rosenstiel award in 1990 and the National Medal of Science in 1990
Embryo
An embryo is an early stage of development of a multicellular diploid eukaryotic organism. In general, in organisms that reproduce sexually, an embryo develops from a zygote, the zygote possesses half the DNA of each of its two parents. In plants and some protists, the zygote will begin to divide by mitosis to produce a multicellular organism, the result of this process is an embryo. First attested in English in the mid-14c, the word embryon derives from Medieval Latin embryo, itself from Greek ἔμβρυον, lit. Young one, which is the neuter of ἔμβρυος, growing in, from ἐν, in and βρύω, swell, be full, the proper Latinized form of the Greek term would be embryum. In animals, the development of the zygote into an embryo proceeds through specific stages of blastula, gastrula. The blastula stage typically features a fluid-filled cavity, the blastocoel, surrounded by a sphere or sheet of cells, in a placental mammal, an ovum is fertilized in a fallopian tube through which it travels into the uterus.
An embryo is called a fetus at an advanced stage of development. In humans, this is from the week of gestation. During gastrulation the cells of the blastula undergo coordinated processes of cell division, invasion, in triploblastic organisms, the three germ layers are called endoderm and mesoderm. The position and arrangement of the layers are highly species-specific, however. For example, in neurogenesis, a subpopulation of cells is set aside to become the brain, spinal cord. Modern developmental biology is extensively probing the molecular basis for every type of organogenesis, including angiogenesis, myogenesis and many others. In botany, a plant embryo is part of a seed, consisting of precursor tissues for the leaves, stem. Once the embryo begins to germinate — grow out from the seed — it is called a seedling and ferns produce an embryo, but do not produce seeds. In these plants, the embryo begins its existence attached to the inside of the archegonium on a parental gametophyte from which the egg cell was generated, the structure and development of the rest of the embryo varies by group of plants.
Once the embryo has expanded beyond the enclosing archegonium, it is no longer termed an embryo, embryos are used in various fields of research and in techniques of assisted reproductive technology. An egg may be fertilized in vitro and the embryo may be frozen for use
Segmentation (biology)
Segmentation in biology refers to the division of some animal and plant body plans into a series of repetitive segments. This article focuses on the segmentation of animal body plans, specifically using the examples of the taxa Arthropoda and these three groups form segments by using a “growth zone” to direct and define the segments. While all three have a segmented body plan and use a “growth zone, ” they use different mechanisms for generating this patterning. Even within these groups, different organisms have different mechanisms for segmenting the body, segmentation of the body plan is important for allowing free movement and development of certain body parts. It allows for regeneration in specific individuals, segmentation is a difficult process to satisfactorily define. Many taxa have some form of repetition in their units. Segmentation in animals typically falls into three types characteristic of different arthropods and annelids, the arthropod fruit fly forms segments from a field of equivalent cells based on transcription factor gradients.
The vertebrate zebrafish uses oscillating gene expression to define segments known as somites, the annelid leech uses smaller blast cells budded off from large teloblast cells to define segments. Although Drosophila segmentation is not representative of the phylum in general. The drosophila as an organism is ideal for genetic screens. Early screens to identify genes involved in development led to the discovery of a class of genes that was necessary for proper segmentation of the drosophila embryo. To properly segment the drosophila embryo, the axis is defined by maternally supplied transcripts giving rise to gradients of these proteins. This gradient defines the pattern for gap genes, which set up the boundaries between the different segments. The gradients produced from gap gene expression define the pattern for the pair-rule genes. The pair-rule genes are mostly transcription factors, expressed in regular stripes down the length of the embryo and these transcription factors regulate the expression of segment polarity genes, which define the polarity of each segment.
Boundaries and identities of each segment are defined, within the arthropods, the body wall, nervous system, kidneys and body cavity are segmented, as are the appendages. Some of these elements are not segmented in their sister taxon, while not as well studied as in Drosophila and zebrafish, segmentation in the leech has been described as “budding” segmentation. Early divisions within the leech embryo result in teloblast cells, which are cells that divide asymmetrically to create bandlets of blast cells
Escherichia coli
Escherichia coli is a gram-negative, facultatively anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms. Most E. coli strains are harmless, but some serotypes can cause food poisoning in their hosts. The harmless strains are part of the flora of the gut, and can benefit their hosts by producing vitamin K2. E. coli is expelled into the environment within fecal matter, the bacterium grows massively in fresh fecal matter under aerobic conditions for 3 days, but its numbers decline slowly afterwards. E. coli and other facultative anaerobes constitute about 0. 1% of gut flora, cells are able to survive outside the body for a limited amount of time, which makes them potential indicator organisms to test environmental samples for fecal contamination. A growing body of research, has examined environmentally persistent E. coli which can survive for extended periods outside of a host, the bacterium can be grown and cultured easily and inexpensively in a laboratory setting, and has been intensively investigated for over 60 years. E. coli is a chemoheterotroph whose chemically defined medium must include a source of carbon, under favorable conditions, it takes only 20 minutes to reproduce. E.
coli is a Gram-negative, facultative anaerobic and nonsporulating bacterium, cells are typically rod-shaped, and are about 2.0 μm long and 0. 25–1.0 μm in diameter, with a cell volume of 0. 6–0.7 μm3. E. coli stains Gram-negative because its cell wall is composed of a peptidoglycan layer. During the staining process, E. coli picks up the color of the counterstain safranin, the outer membrane surrounding the cell wall provides a barrier to certain antibiotics such that E. coli is not damaged by penicillin. Strains that possess flagella are motile, the flagella have a peritrichous arrangement. E. coli can live on a variety of substrates and uses mixed-acid fermentation in anaerobic conditions, producing lactate, ethanol, acetate. Optimum growth of E. coli occurs at 37 °C, and it uses oxygen when it is present and available. It can, continue to grow in the absence of oxygen using fermentation or anaerobic respiration, the ability to continue growing in the absence of oxygen is an advantage to bacteria because their survival is increased in environments where water predominates.
The bacterial cell cycle is divided into three stages, the B period occurs between the completion of cell division and the beginning of DNA replication. The C period encompasses the time it takes to replicate the chromosomal DNA, the D period refers to the stage between the conclusion of DNA replication and the end of cell division. The doubling rate of E. coli is higher when more nutrients are available, the length of the C and D periods do not change, even when the doubling time becomes less than the sum of the C and D periods. At the fastest growth rates, replication begins before the round of replication has completed, resulting in multiple replication forks along the DNA
Hedgehog signaling pathway
The Hedgehog signaling pathway is a signaling pathway that transmits information to embryonic cells required for proper cell differentiation. Different parts of the embryo have different concentrations of hedgehog signaling proteins, the pathway has roles in the adult. Diseases associated with the malfunction of this pathway include basal cell carcinoma, the Hedgehog signaling pathway is one of the key regulators of animal development and is present in all bilaterians. The pathway takes its name from its polypeptide ligand, a signaling molecule called Hedgehog found in fruit flies of the genus Drosophila. Hh is one of Drosophilas segment polarity gene products, involved in establishing the basis of the fly body plan, the molecule remains important during stages of embryogenesis and metamorphosis. Mammals have three Hedgehog homologues, Desert and Sonic, of which Sonic is the best studied, the pathway is equally important during vertebrate embryonic development and is therefore of interest in evolutionary developmental biology.
In knockout mice lacking components of the pathway, the brain, musculature, gastrointestinal tract, recent studies point to the role of Hedgehog signaling in regulating adult stem cells involved in maintenance and regeneration of adult tissues. The pathway has implicated in the development of some cancers. Drugs that specifically target Hedgehog signaling to fight this disease are being developed by a number of pharmaceutical companies. In the 1970s, a problem in developmental biology was to understand how a relatively simple egg can give rise to a complex segmented body plan. In 1995, they shared the Nobel Prize with Edward B. Lewis for their work studying genetic mutations in Drosophila embryogenesis, the Drosophila hedgehog gene was identified as one of several genes important for creating the differences between the anterior and posterior parts of individual body segments. The fly hh gene was cloned in 1992 by the labs of Jym Mohler, Philip Beachy. Some hedgehog mutants result in abnormally-shaped embryos that are unusually short, rather than the normal pattern of denticles, hedgehog mutant larvae tend to have solid lawns of denticles.
The appearance of the stubby and hairy larvae inspired the name hedgehog, the SCF complex targets the 155 kDa full length Ci protein for proteosome-dependent cleavage, which generates a 75 kDa fragment. CiR builds up in the cell and diffuses into the nucleus, the steps leading to Ci protein proteolysis include phosphorylation of Ci protein by several protein kinases, PKA, GSK3β and CK1. The Drosophila protein Slimb is part of an SCF complex that targets proteins for ubiquitylation, Slimb binds to phosphorylated Ci protein. In the absence of Hh, a transmembrane protein called Patched acts to prevent high expression. Patched has sequence similarity to known membrane transport proteins, when extracellular Hh is present, it binds to and inhibits Patched, allowing Smoothened to accumulate and inhibit the proteolytic cleavage of the Ci protein
