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Terms and Conditions

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1. GENERAL PROVISIONS By accessing or using this website or any of its contents, you hereby agree to these terms and conditions, and consent to be bound by it. If you do not agree, you should not access or use this website. The authors of this website reserve the right to change these terms and conditions at any time without prior notice. Your continuance in accessing or using this website signifies your acceptance and agreement with these terms and conditions. The authors of this website reserve the right to change its contents, and to restrict, withdraw, cancel, disconnect, deactivate, suspend or discontinue any or all of its contents without prior notice. 2. COPYRIGHT AND FAIR USE This website is operated as a free service for the public. Some materials contained herein, however, are protected by copyright. You must abide by all the copyright notices or restrictions set by their respective copyright holders accordingly. 2.1. ORIGINAL WORKS The use and distribution, wit
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Regulaton of Gene Expression

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Gene regulation is the process of promoting or suppressing the expression of genes. Regulation can occur anywhere during transcription or translation. Sometimes, gene regulation also happens even before transcription. This is called epigenetic modification. Epigenetic modifications  occurs when compounds attach to DNA genes and alters gene expression. A good example of this is methylation. Methylation happens when methyl attaches to histones. This do not alter the DNA sequence. However, this gets the the DNA tightly wound around the histones. Transcription factors cannot bind to the DNA and the genes, therefore, cannot be expressed. Histone acetylation is another form of Epigenetic modifcation. This results in loosed packing of nucleosomes making it accessible for the transcription factors to bind enabling gene expression. Expression of genes regulated during transcription or translation results to either suppression or promotion of RNA or protein synthesis. A  Certain s
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Gene expression: Eukaryotes

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Gene expression  is  the molecular process by which DNA  is converted into a functional product called proteins[1]. The two key steps in the production of proteins is Transcription (DNA to RNA) and Translation (RNA to proteins)[1][2]. The processes are different in prokaryotes and eukaryotes. EUKARYOTIC GENE EXPRESSION Unlike prokaryotes, eukaryotic cells have nucleus. This means that transcription and translation cannot occur at the same time. Transcription is carried out inside the nucleus of the cell. Transcription a) Initiation The initiation of transcription in eukaryotes requires the participation of the promoter region, transcription factors, and RNA polymerase. There are several core promoter elements in eukaryotes. The most commonly studied is the TATA box . This is located 25-30 base pairs upstream from the transcription start site. The TATA box is where the transcription factors bind. Transcription factors are composed of several proteins. The first tr
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Cell to cell communication

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Cells need to communicate with each other to enable proper physiological response.  The movements of the body, for example, are controlled by the brain and the muscles. For this to happen, cells of the brain and the muscle tissues must interact. Communication between cells are usually through chemical signals. Chemical signals, called ligand, are released from a "sending cell" into the extracellular space. The target cells must have the correct receptor for that signal. Once the signal molecule binds to the correct receptor, the target cell changes in conformation to allow the signal molecule to enter the cell. Once the ligand is inside the target cell, chemical reactions take place affecting the activity inside the cell. I-Types of cell signaling There are four types of cell-cell signaling mainly differing in the distance the signal travels through. These are: Autocrine signaling Signaling by direct contact Paracine signaling Endocrine signaling 1. Auto
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Environmental Factors Affecting Growth and Development

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Phenotypic characters are not only an expression of inherited genes, rather they are influenced by environmental factors as well. Environmental factors that influence phenotypic expression can be temperature, diet, and presence of predators. I - Phenotypic plasticity Phenotypic plasticity is the ability of an organism to react to an environmental input with a change in form, state, movement, or rate of activity. There are two main types of phenotypic plasticity: reaction norm and polyphemism. A. Reaction norm In reaction norm, the genome encodes a range of potential phenotypes, and the environment that the individual is exposed to determines what phenotype should be expressed.  B. Polyphemism The genome only encodes for the phenotype that would best suit the organism in the environment it is in. The environmental factors that usually influences the organism's phenotype are temperature, diet, and presence of predator. 1. Temperature-induced polyphemism
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Mammalian Development: Formation of blastocyst to development of organs

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II - Early Development A. Cleavage Cleavage is when the fertilized egg divides several times to create a multicellular embryo. This process occurs as the embryo travels along the oviduct towards the uterus (figure 1). Cleavage ends when a blastocyst is formed. 1. Events in the ampulla The first cleavage starts when "arrested" meisos in the egg resumes. At this time sperm DNA are involved. The first cleavage is usually meriodional, producing 2 cells (figure 2a). Production of four cells is achieved through rotational cleavage where one blastomere divides meriodionally and the other one equatorially (figure 2b).  2. Events in the Isthmus The blastomeres divide further to produce 8 cells. At this point  compaction  happens. During compaction, blastomeres adhere to each other forming a compact ball of cells. These compacted cells divide further to produce a  morula (figure 2d). The 8-cell morula is composed of a small group of internal cells which
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Mammalian Development: Fertilization

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I- Fertilization Fertilization accomplishes two objectives: 1. sex and 2. reproduction. Sex is accomplished when genes from two parents are combined. Reproduction is accomplished when there is successful generation of a new organism. A. Sex 1. Contact and recognition between sperm and egg Mammalian sperm and egg interaction takes place inside the female reproductive tract. Fertilization takes place at the ampulla . For fertilization to happen, the sperm has to get to the ampulla. This is accomplished by means of translocation and capacitation. a. Translocation For sperm to travel from the vagina to the oviduct, it is assisted by several processes. These processes are sperm motility, uterine muscle contraction, and sperm rheotaxis. Sperm motility is accomplished by flagellar action. The flagellar action of the sperm alone, however, cannot transport it to the site of the egg at they right time. Translocation of sperm is further assisted by uterine muscle con
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Effects of Climate Change on Animal Physiology

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The study of physiology basically deals with the functions and mechanisms within a living system. These functions and mechanisms may be influenced by the external environment. Changes in temperature for example can affect the growth, reproduction, and  survival of organisms. Thus, studying animal physiology can help us determine the effect of climate change on the diversity and distribution of organisms. Changes in temperature Changes in environmental temperatures have a great influence on species geographical distribution, population collapse, species extinction, and on an organism's growth and reproduction[1].  Molecular, cellular, and systemic processes within a living system function at a limited range of temperature (thermal window). Performance in an organism's growth, reproduction, foraging, immune competence, behaviors and competitiveness is directly affected by climatic warming. Such performance is supported by increase in oxygen consumption by aerobic
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Gene expression: Prokaryotes

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Gene expression is  the molecular process by which DNA  is converted into a functional product called proteins[1]. The two key steps in the production of proteins is Transcription (DNA to RNA) and Translation (RNA to proteins)[1][2]. The processes are different in prokaryotes and eukaryotes. PROKARYOTIC GENE EXPRESSION Transcription a) Initiation In prokaryotes, like bacteria, the chromosome is a covalently-closed circle. For transcription to occur, the DNA double helix must partially unwind. The unwound region is called the transcription bubble . A holoenzyme (a fully functioning enzyme) and promoter is necessary for the initiation of transcription[3]. Prokaryotic RNA polymerase  is the holoenzyme which assembles each time a gene is transcribed, and disassembles once transcription is complete. It is composed of 5 polypeptide subunits. These subunits are α, α, β, β', and σ[3]. α-subunits are used to assemble the polymerase on the DNA β-subunit binds to t
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Evolution: the core of Biology

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The key to understanding Biology is through the study of Evolution[1]. Evolution is what makes life possible[2]. How life started and how life came to be is all through the process of evolution. Evolution can explain how complex organisms came to be, how simple forms stay simple, and how organisms are related to each other. Evolution not only explains the development of visible morphological characters. At the molecular level, functions and forms of genes are influenced by the process of evolution as well[1]. To further understand how evolution is the heart of life processes, we need to understand the concepts and ideas that explain life: the theories of evolution. History of Evolution Before the conception of evolution, people believed in the paradigm of the   ' Fixity '   of species[4], that everything was created through Divine Conception [5].   The accepted idea is that every single organism was created as it is, nothing is mutated, everything is unchanging
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