1st Bimonthly Transes (1-7) PDF

UNIT 2: EMBRYOLOGY, GENETICS, CELLS AND TISSUES MICROVILLI - extensions of the plasma TRANSPORTS ACROSS PLASMA MEMBRANE...

UNIT 2: EMBRYOLOGY, GENETICS, CELLS AND TISSUES MICROVILLI - extensions of the plasma TRANSPORTS ACROSS PLASMA MEMBRANE membrane containing microfilaments. Increases 1st year 1st Semester (2nd week) LDCU-COM surface area of the plasma membrane for Transmembrane Proteins & Membrane Transport absorption and secretion; modified to form sensory receptors. Diffusion - transports small, nonpolar molecules DEFINITION & DESCRIPTION OF CELLS AND ITS BASIC FUNCTIONS LIST OF DIFFERENT CELL STRUCTURES & FUNCTIONS directly through the lipid bilayer. Lipophilic (fat-soluble) NUCLEOLUS - the largest nuclear organelle and is molecules diffuse through membranes readily, water PLASMA MEMBRANE - Lipid bilayer composed of the primary site of ribosome subunit biogenesis in very slowly. phospholipids & cholesterol, protein are attached eukaryotic cells. It is assembled around arrays of 1. CELLS AND ITS FUNCTION to lipid bilayer. Outer boundary of the cell, ribosomal DNA genes, forming specific Channels - are multipass proteins forming chromosomal features known as nucleolar transmembrane pores through which ions or small Basic (membrane- bound) unit of all living things controls entry and exit of substances, protein organizing regions (NORs) which are the sites of molecules pass selectively. Cells open and close Building blocks of the body function, marker molecules for cells to identify ribosomal DNA transcription. specific channels. for Na+, K+, Ca2+, and other ions in Provide structure for the body’s tissues and organs each other. response to various physiological stimuli. Water Ingest nutrients converting them to energy NUCLEUS - enclosed by nuclear envelop, a Perform specialized functions PLASMA MEMBRANE & ITS COMPOSITION molecules usually cross the plasma membrane double membrane w/ nuclear pores. Contains through channel proteins called aquaporins. chromatin. Control center of the cell, regulates Phospholipids - amphipathic, consists of two 1.1. EUKARYOTIC CELLS protein synthesis and chemical reactions of the nonpolar (hydrophobic) long chained fatty acids Carriers - are transmembrane proteins that bind cell. small molecules and translocate them across the linked to a charged polar (hydrophilic) that bears Endoplasmic reticulum present membrane via conformational changes. RIBOSOMES - macromolecular machines, about the phosphate group. It is made of glycerol, two- Mitochondria present 20 × 30 nm in size, which assemble polypeptides fatty acid tails, and phosphate-linked head group. Transport by Vesicles: Endocytosis & Exocytosis Cytoskeleton present from amino acids on molecules of transfer RNA Two phospholipid layers with their tails pointing Phagocytosis - (“cell eating”) is the ingestion of (tRNA) in a sequence specified by mRNA. inward, an arrangement called phospholipid particles such as bacteria or dead cell remnants. Larger ribosomes bilayer. (KEYWORD: PHAGOSOME) Membrane-bound nucleus ROUGH ENDOPLASMIC RETICULUM - Pinocytosis - (“cell drinking”) involves smaller Cholesterol - composed of four carbon rings, membranous tubules and flattened sacs with invaginations of the cell membrane which fuse and 1.1 PROKARYOTIC CELLS attached ribosomes. Synthesizes proteins, found alongside phospholipids. Restricting their movements and modulating the fluidity of all entrap extracellular fluid and its dissolved contents. Endoplasmic reticulum absent transported to Golgi apparatus. The latter process, called transcytosis, accomplishes membrane components. Mitochondria absent bulk transfer of dissolved substances across the cell. SMOOTH ENDOPLASMIC RETICULUM - Proteins - extend partway into the plasma Receptor-mediated endocytosis - Receptors for Cytoskeleton absent membranous tubules and flattened sacs without membrane, cross the membrane entirely, or be many substances, such as low-density lipoproteins and Smaller ribosomes ribosomes. Makes lipids and carbohydrates, loosely attached to its inside or outside face. Major protein hormones, are integral membrane proteins at detoxification, calcium storage. constituent of the PM (50%) Integral proteins are the cell surface. High-affinity binding of such ligands to No membrane-bound nucleus incorporated directly within the lipid bilayer, their receptors causes these proteins to aggregate in GOLGI APPARATUS - stacked flattened whereas peripheral proteins are bound to one of special membrane regions that then invaginate and membrane sacs. Modifies, packages, and the two membrane surfaces, particularly on the pinch off internally as vesicles. distributes proteins and lipids for cytoplasmic side. Integration of the proteins within Endocytosis - Macromolecules normally enter cells by secretion/internal use. the lipid bilayer is mainly the result of hydrophobic being enclosed within folds of plasma membrane LYSOSOME - membrane-bound vesicle pinched interactions between the lipids and nonpolar amino (often after binding specific membrane receptors) off from Golgi apparatus. Contains digestive acids of the proteins. Also acts as receptors, that which fuse and pinch off internally as spherical enzymes (cellular digestion). acts on cell adhesion, cell recognition, and the cytoplasmic vesicles (or vacuoles). response to protein hormones. Exocytosis - Movement of large molecules from inside 1.2 SPECIALIZED CELLS AND THEIR GENERAL CELLULAR ACTIVITY PEROXISOME - membrane-bound vesicle. Site of lipid and amino acid degradation; breaks down Carbohydrate group - present only on the outer to outside the cell usually involves vesicular transport. hydrogen peroxide. surface of the plasma membrane and are attached to proteins, forming glycoproteins, or lipids, GERM LAYERS AND THEIR DERIVATIVES PROTEASOME - tube-like protein complexes in forming glycolipids. the cytoplasm. Breaks down protein in cytoplasm. Trilaminar germ disc: An embryonic disc made up of three layers called ectoderm (outer), endoderm (inner) and MITOCHONDRIA - spherical, rod-shaped, or FUNCTIONS OF THE PLASMA MEMBRANE mesoderm (middle). It is formed during the early threadlike structures. Enclosed by double gastrulation (3rd week of development) phase. membrane. Has projections called cristae. Major 1. Physical barrier: Establishes a flexible site of ATP synthesis of oxygen is available ECTODERM— Outermost layer of the three germ layers. boundary, protects cellular contents, and Surface ectoderm CENTRIOLES - cylindrical organelles with triplets supports cell structure. Phospholipid adenohypophysis of parallel microtubules. Located in the bilayer separates substances inside and lens of the eye centrosome. Centers for microtubule formation. outside the cell. sensory organs Determine cell polarity during cell division & forms 2. Selective permeability: Regulates entry ear basal bodies of cilia and flagella. and exit of ions, nutrients, and waste olfactory epithelium MICROTUBULES - rigid hollow rods that are molecules through the membrane. epithelial linings approx25nm in size that forms the cytoskeleton. 3. Electrochemical gradients: Establishes oral cavity Regulates cell growth and movement, as well as and maintains an electrical charge lower anal canal key signaling events. difference across the plasma membrane. external auditory meatus 4. Communication: Contains receptors epidermis, hair, and nails CILIA - extensions of plasma membrane that recognize and respond to molecular mammary, sweat, and salivary glands containing parallel microtubules. 10 micrometers signals. Neuroectoderm - CNS and brain brain - all neurons in length. Moves materials over the surface of the cells. within brain and spinal cord/CNS neurohypophysis FLAGELLLUM - extension of the plasma oligodendrocytes membrane containing doublets of parallel astrocytes microtubules. 55 micrometers in length. In ependymal cells humans, propel spermatozoa. pineal gland retina  MESODERM— Middle layer of the three germ layers. Muscular Tissue Muscle (smooth, cardiac, and skeletal) - muscle tissue is composed of elongated cells Epithelial Cells and their Surfaces SECRETORY (GLANDULAR) EPITHELIA Dermis and subcutaneous layers of skin specialized for contraction, has moderate amount of The major function in many epithelial cells is APICAL SURFACES Bone, cartilage, and connective tissue ECM and specializes for body movements synthesis and secretion of specialized products; Microvilli Dura mater organs composed primarily of such epithelia are called Nervous Tissue small membrane projections with cores of actin filaments that Serous linings of body cavities glands. - is composed of cells with long, fine processes generally function to increase epithelial cells’ apical surface peritoneum Exocrine glands have epithelial ducts carrying specialized to receive, generate, and transmit nerve area for absorption. Spleen secretions to specific sites; the ducts of simple glands impulses. Has very small amount of ECM. Stereocilia Cardiovascular structures are unbranched and those of compound glands are long microvilli with specialized mechanosensory function in Lymphatics branched. cells of the inner ear and for absorption in tissues of the male Laryngeal cartilage The secretory portions of exocrine glands may form reproductive tract. Blood: RBCs, WBCs, Kupffer cells, and microglia round, saclike acini (also called alveoli) or elongated Cilia Urogenital structures tubules; both types of secretory units may themselves long, highly motile apical structures, larger than microvilli, and > male: testes, epididymis, ductus deferens, seminal vesicle, branch. containing internal arrays of microtubules. and ejaculatory duct Endocrine glands lack ducts; secreted substances > female: ovaries, uterus, uterine tubes, and upper 1/3 of are hormones carried throughout the body by the LATERAL SURFACES vagina interstitial fluid and blood, with specificity produced by Tight or occluding junctions Kidneys the hormone receptors of target cells. Form a seal between adjacent cells. Adrenal cortex Glands have three basic secretory mechanisms: Adherent or anchoring junctions merocrine, which uses exocytosis; holocrine, in which Sites of strong cell adhesion. terminally differentiated cells filled with lipid product ENDODERM — inner layer of the three germ layers. >Zonula adherens: encircle epithelial cells just below are released; and apocrine, in which apical, Epithelium lining of respiratory: their tight junctions. Features & Functions of Epithelium product-filled areas of cells are extruded. urinary: urinary bladder, female urethra, and majority of >Desmosomes or maculae adherens: scattered, spot- Intercellular adhesion and other junctions Exocrine glands producing mucus, or similar male urethra like attachment sites. Tight or occluding junctions individual cells called goblet cells, are called mucous GI tract Gap junctions Form a seal between adjacent cells. glands. biliary system Channels for communication between adjacent cells. lower 2/3 of vagina Adherent or anchoring junctions BASAL MEMBRANE middle ear cavity and auditory tube Sites of strong cell adhesion. BASAL SURFACES Zonula adherens Hemidesmosomes a thin extracellular layer that commonly trachea, bronchi, and lungs Encircles epithelial cells just below their tight Composed of transmembrane integrins attach cells to proteins consists of two layers, the basal lamina and Liver junctions. of the basal lamina. reticular lamina. Parathyroid Thyroid follicular cells Macula adherens COVERING (LINING) EPITHELIA Attach to and supporting the overlying epithelial Thymus Scattered, spot-like attachment sites. tissue Hemidesmosomes Stratified squamous keratinized epithelium - found mainly in Pancreas It separates tissues and protect them from Composed of transmembrane integrins attach cells the epidermis of skin, where it helps prevent dehydration from Parafollicular (C) cells of thyroid mechanical stress the tissue. Its cells form many layers, with the less differentiated to proteins of the basal lamina. Exchange of substances between epithelial tissues cuboidal cells near the basement membrane. These cells have NEURAL CREST Gap or communicating junctions and connective tissues occurs by diffusion. many desmosomes and become more irregular in shape and PNS and nearby non-neural structures Channels for communication between adjacent cells. They form a surface along which epithelial cells then flatten as they accumulate keratin in the process of ANS Covering, lining, and protecting surfaces keratinization and are moved progressively toward the skin migrate during growth or wound healing enteric nervous system (eg, epidermis) surface, where they become thin, metabolically inactive packets restrict passage of larger molecules between ganglia (dorsal root, cranial, and autonomic) Absorption (eg, the intestinal lining) (squames) of keratin lacking nuclei. epithelium and connective tissue cranial nerves Secretion (eg, parenchymal cells of glands) participate in filtration of blood in the kidneys. celiac ganglion Stratified squamous nonkeratinized epithelium lines moist Basement membrane play formative roles in melanocytes internal cavities (eg, mouth, esophagus, and vagina) where shaping tissues. (Morrisey and Sherwood, 2015) chromaffin cells of adrenal medulla Types of Epithelial Cells water loss is not a problem. Here the flattened cells of the enterochromaffin cells surface layer retain their nuclei and most metabolic functions. Schwann cells Shape pia and arachnoid Squamous epithelium: Squamous epithelial bones of the skull cells are flat and sheet-like in appearance. odontoblasts Cuboidal epithelium: Cuboidal epithelial cells aorticopulmonary septum are cube-like in appearance, meaning they have equal width, height and depth. TISSUES Columnar epithelium: Columnar epithelial cells are column-like in appearance, meaning they are Connective Tissue taller than they are wide. - provides a matrix that supports and physically connects other Arrangement tissues and cells together to form the organs of the body. The interstitial fluid of connective tissue gives metabolic support to cells Simple: A simple epithelium means that there’s as the medium for diffusion of nutrients and waste products. only one layer of cells. Characterized by cells producing very abundant ECM; Stratified: A stratified epithelium is made up of more than one layer of cells. Epithelial Tissue Pseudostratified: A pseudostratified epithelium is made up of closely packed cells that appear to - are composed of closely aggregated polyhedral cells adhering be arranged in layers because they’re different strongly to one another and to a thin layer of ECM, forming cellular sizes, but there’s actually just one layer of cells. sheets that line the cavities of organs and cover the body surface. Epithelia (Gr. epi, upon + thele, nipple) line all external and internal surfaces of the body and all substances that enter or leave an organ must cross this type of tissue. CONNECTIVE TISSUES Hypoblast: Caspases (for cysteine aspartic acid–specific proteases) - exist as inactive precursors BONE Located ventrally near the blastocyst cavity (procaspases), are activated to produce cellular - classified as either compact or spongy, depending on how Some hypoblast cells will form the anterior visceral morphologic changes during apoptosis. its extracellular matrix and cells are organized. endoderm, which becomes the cranial end of the Apoptotic Bodies - small enclosed-membraned cells Bones are organs composed of several different connective embryo that have undergone apoptosis; coated with tissues A cavity emerges within the hypoblast to form the phosphatidylserine bone or osseous tissue (OS-e¯-us), primary yolk sac. Phagocytosis - process of elimination of the debris the periosteum On the ventral side of the yolk sac, the hypoblast red and yellow bone marrow expands to form the extraembryonic mesoderm Necrosis - cells that die as a result of an acute injury the endosteum (a membrane that lines a space within Somatic mesoderm: lines the usually swell and burst due to loss of cell membrane bone that stores yellow bone marrow). cytotrophoblast and amnion integrity. Splanchnic mesoderm surrounds the yolk CARTILAGE sac EXTRINSIC AND INTRINSIC SIGNALS IN - form of connective tissue in which the cells and fibers are Epiblast: APOPTOSIS embedded in a gel-like matrix, the fibers lending firmness and resilience. A fibrous membrane called the Extrinsic signals bind to cell surface receptors Located dorsally (Fas ligand and granzyme B/perforin). perichondrium covers the cartilage except on the exposed A small cavity will emerge within the epiblast to form surfaces in joints. the amniotic cavity. BLOOD COMPONENTS Intrinsic signals (the release of cytochrome c from mitochondria) - connective tissue with a liquid extracellular matrix and formed elements. Blood plasma - pale yellow fluid that consists mostly of All of these can trigger cell death. water and contained dissolved substances. RBC - oxygen carrying unit of the blood WBC - phagocytosis, fights off bacteria & viruses/malignant diseases. Platelet - coagulation, stops bleeding MUSCLE TISSUE - composed of cells specialized for contraction and generation of force. Muscular tissues generate heat that warms the body, and provide motion, pumps blood, and for structural support. Smooth Muscle Tissue - lines visceral organs, APOPTOSIS involuntary, not striated, centrally-located nucleus, It is a rapid, highly regulated cellular activity that shrinks and spindle-shaped. eliminates defective and unneeded cells. Cardiac Muscle Tissue - uninucleated, branching fibers, Eliminated in a manner that does not provoke a local has striations and intercalated disks, involuntary. inflammatory reaction in the tissue. Skeletal Muscle Tissue - cylindrical, multinucleated, Occurs when cells are no longer needed or become a striated and under voluntary control. threat to the organism NERVOUS TISSUE NEURULATION Bcl-2 family - cytoplasmic proteins that controls the onset - it consists of only two principal types of cells: of apoptosis; -a process of formation of neural plate, neural folds and first identified by a genetic mutation in a specific B-cell closure of these folds to form neural tube. Neurons - They convert stimuli into electrical signals lymphoma - is lengthening of the neural plate and body axis by the called nerve action potentials (nerve impulses) and conduct these action potentials to other neurons, to phenomenon of convergent extension, whereby there is a Specific Bcl-2 proteins induce a process with the following lateral to medial movement of cells in the plane of the muscle tissue, or to glands. Consists of Cell Body, features: ectoderm and mesoderm. Dendrites, Axon. 1. Loss of mitochondrial function and caspase activation: Neuroglia - Do not generate or conduct nerve release of cytochrome c - activation of proteolytic enzymes impulses. It supports the activities of neurons. It also called caspases. nourish and protect neuron and maintain interstitial 2. Fragmentation of DNA: fluid that bathes them. Endonucleases are activated which makes the DNA into small fragments EMBRYOBLAST & TROPHOBLAST DEVELOPMENT 3. Shrinkage of nuclear and cell volumes: Cytoskeleton and chromatin destruction EMBRYOBLAST 4. Cell membrane changes: - The embryoblast gives rise to the bilaminar disc Forms “blebs” and amniotic cavity. The embryoblast differentiates 5. Formation and phagocytic removal: into the epiblast and hypoblast. Together, they are Remnants - Apoptotic bodies referred to as the bilaminar disc. The process begins around the 8th day of gestation.  STAGES OF NEURULATION CELLULAR RESPIRATION 1.Neuroectoderm and neural plate stage Cellular respiration is the oxidation of glucose to produce ATP. In presomitic period (16th–19th day): Involves 4 sets of reactions: Surface ectoderm differentiates and thickens in the center, GLYCOLYSIS becoming the neural plate or medullary plate. Notochord acts as a primary inducer for neural plate A set of reactions in which one glucose molecule is oxidized formation and differentiation and two molecules of pyruvic acid are produced. Neural plate grows rapidly and elongates craniocaudally in The reactions also produce two molecules of ATP and two the length. energy containing NADH + H+ Location: Cytoplasm 2. Neural folding stage 2 Phases: Preparative and ATP Generating Continuous growth of neural plate makes it depressed in the Anaerobic = lactic acid midline. This linear depression is called neural groove. Elevated margins of neural groove form neural folds. At the junctional zone of neural plate and surface ectoderm, the cells differentiate to form neural crest. Neural crest forms peripheral and autonomic nerves. 3. Stage of neural tube formation Due to rapid proliferation of neural plate, the neural folds Electron transport chain reactions come closer to each other and start fusion in the midline Occurs in the inner membrane of mitochondria forming the neural tube. These reactions oxidize NADH + H+ and FADH2 Fusion begins in cervical region and extends in cranio-caudal and transfer their electrons through a series of direction. electron carriers. Neural tube forms central nervous system. 4. Stage of neural tube closure Neural tube remains open at cranial end as cranial (anterior) neuropore and at caudal end as caudal (posterior) neuropore. FORMATION OF ACETYL COENZYME A Open neural tube facilitates circulation of amniotic fluid A transition step that prepares pyruvic acid for entrance into through the lumen of neural tube; provides nutrition to the Krebs cycle. rapidly developing neuroectodermal cells before the This step also produces energy-containing NADH + H+ plus establishment of sufficient uteroplacental circulation. carbon dioxide (CO2) Cranial neuropore closes by 25th day of IUL, whereas caudal neuropore closes by 27th day of IUL. Closure of cranial neuropore occurs at the 20 somite stage, whereas closure of posterior neuropore occurs at 25 somite stage. CELL MATURATION Non-closure of neuropore results in neural tube defects. In later life, the location of anterior neuropore is represented The process of cells maturing and specializing, by lamina terminalis, whereas posterior neuropore by losing their ability to split and become new cells. terminal ventricle (lies in caudal end of spinal cord). The regular sequence of events that produce GENETIC CODE new cells. Improved knowledge about how each phase of the cell cycle is controlled and how the - The letters A, G, T, and C correspond to the quality of molecular synthesis, particularly DNA nucleotides found in DNA. Within the protein-coding KREB CYCLE PROCESS OF FORMATION OF NEURAL CREST replication, is monitored has led to genes, these nucleotides are organized into three-letter Hans Krebs Neural crest is a portion of lateral margins of the neural understanding the causes of many types of code words called codons, and the collection of these Other names: Citric Acid Cycle/Tricarboxylic Acid Cycle plate at its junction with rest of ectoderm. cancer, in which cells proliferate without those codons, once transcribed into mRNA, makes up the Reactions occur in the matrix of mitochondria and consist of At the time of separation of neural tube from surface controls. genetic code. a series of oxidation–reduction reactions and ectoderm, cells of neural crest also get separated and come · must be at least 20 distinct codons that make decarboxylation reactions that release CO2. to lie between ectoderm and neural tube. PHASES up the genetic code. These reactions oxidize acetyl coenzyme A and produce CO2, Thus, neural plate forms neural tube and neural crest M Phase (MITOSIS) ATP, NADH + H+, and FADH2. cells. G1 (the time gap between mitosis and the beginning of Nucleotide: Watson-Crick base pairing Neural crest cells further divide to form dorsal mass and DNA replication) ventral mass S (the period of DNA synthesis) Purine G2 (the gap between DNA duplication and the next · Adenine - Thymine(DNA)/Uracil(RNA) mitosis). Pyramidine · Guanine – Cytosine  PROTEIN SYNTHESIS THE DNA–GENETIC SYSTEM CONTROLS CELL REPRODUCTION Elongation. DNA polymerases are responsible for creating the new strand by a process called elongation. RNA The genes and their regulatory mechanisms determine Because replication proceeds in the 5′ to 3′ direction on Two major classes: cell growth characteristics and when or whether cells will the leading strand, the newly formed strand is · Protein coding RNAs divide to form new cells. continuous. The lagging strand begins replication by o mRNAs binding with multiple primers that are only several bases · Non-protein coding RNAs DNA apart. o rRNAs is the genetic material of cells o tRNAs contains genes, which determine the structure of proteins DNA polymerase then adds pieces of DNA, called Okazaki o lncRNAs a double helix-two strands of nucleotides joined together fragments, to the strand between primers. This process of o snRNAs to form a twisted, ladder-like structure. replication is discontinuous because the newly created o miRNAs Okazaki fragments are not yet connected. An enzyme, DNA o siRNAs NUCLEOTIDES ligase, joins the Okazaki fragments to form a single unified basic building blocks of DNA and RNA strand. mRNAs, rRNAs, tRNAs directly involved in protein synthesis NITROGENOUS BASES Termination. After the continuous and discontinuous other RNAs participate in either mRNA splicing or strands are both formed, the enzyme exonuclease modulation of gene expression by altering mRNA Single-ringed molecules removes the RNA primers from the original strands, and RNA is synthesized from DNA template Thymine the primers are replaced with appropriate bases. o Steps: TRANSLATION CYCLE Cytosine Another exonuclease “proofreads” the newly formed 1. INITIATION Uracil DNA, checking and clipping off any mismatched or 1. Small ribosomal unit binds to mRNA 2. ELONGATION unpaired residues. 2. tRNA with an amino acid and an anticodon will now 3. TERMINATION Double-ringed molecules. attach to its complement codon which is the start Adenine Topoisomerase, can transiently break the phosphodiester codon AUG or methionine. Guanine bond in the backbone of the DNA strand to prevent the DNA 3. The large ribosomal unit will join in front of the replication fork from being overwound. E site Chemical and Physical Events of DNA Replication P site 1. Both strands of the DNA in each chromosome are The process of replication therefore produces two DNA A site replicated, not just one of them molecules, each with one strand from the parent DNA and 4. charged tRNA will attach to its complementing codon 2. Both entire strands of the DNA helix are replicated from one new strand. at the A site and creating a peptide bond among the end to end, rather than small portions of them, as occurs amino acid. The the uncharged tRNA will now be in the transcription of RNA. DNA replication is often described as semiconservative; released to the E site. And the cycle goes on. 3. Multiple enzymes: DNA polymerase, which is comparable half of the chain is part of the original DNA molecule and 5. Until it terminates when it reaches a stop codon then to RNA polymerase, are essential for replicating DNA. It half is brand new. a release factor will bind. attaches to and moves along the DNA template strand, 6. Releasing the protein and the entire complex will adding nucleotides in the 5′ to 3′ direction MECHANISM OF MOLECULAR (GENETIC) CONTROL OF dissociate and will be used to another protein GROWTH AND DEVELOPMENT synthesis. DNA ligase- causes bonding of successive DNA nucleotides to one another, using high-energy phosphate bonds to The mechanisms that maintain proper numbers of the MUTATIONS energize these attachments. different types of cells in the body are still poorly TRANSCRIPTION CYCLE Silent mutation – Third nucleotide is changed understood. However, experiments have shown at least 1. RNAP binds to DNA strands and locates the promoter Missense effect – different amino acid is incorporated Replication fork formation. Before DNA can be three ways in which growth can be controlled. making the RNAP-promoter complex and melts DNA strand Nonsense codon - premature replicated, the double-stranded molecule must be 1. Growth often is controlled by growth factors that TBP “unzipped” into two single strands. come from other parts of the body. TATA box 2. Most normal cells stop growing when they have run out RNA 2. Open promoter complex/preinitiation complex. This uncoiling is achieved by DNA helicase enzymes that of space for growth. 3. Chain initiation: RNAP catalyzes coupling of first base to break the hydrogen bonding between the base pairs of the 3. Cells grown in tissue culture often stop growing when Messenger RNA(mRNA) the second. DNA, permitting the two strands to separate into a Y shape minute amounts of their own secretions are allowed to Carries the code for the synthesis of a specific 4. Promoter clearance known as the replication fork, the area that will be the collect in the culture medium protein RNA polymerase II/ template for replication to begin. Produced in the nucleus GTF Telomeres - Prevent the Degradation of Chromosomes. Transfer RNA(tRNA) Moves away from promoter Replication progresses only in the 5′ to 3′ direction. At the A telomere is a region of repetitive nucleotide sequences carry the amino acids to the ribosome with its 5. Chain Elongation replication fork one strand, the leading strand, is oriented in located at each end of a chromatid. anticodon Successive residues are added the 3′ to 5′ direction, toward the replication fork, while the Ribosomal RNA (rRNA) 6. Chain termination and RNAP release lagging strand is oriented 5′ to 3′, away from the replication Telomeres serve as protective caps that prevent the Component of ribosome fork. Because of their different orientations, the two strands chromosome from deterioration during cell division. Molecule in cells that forms part of the protein- Exons – RNA sequence that appear in mature RNAs are replicated differently. synthesizing organelle known as a ribosome and Introns – Intervening Sequence Regulation of Cell Size. Cell size is determined almost that is exported to the cytoplasm to help translate Spliced by Spliceosome(snRNAs) Primer binding - Once the DNA strands have been entirely by the amount of functioning DNA in the the information in messenger RNA (mRNA) into separated, a short piece of RNA called an RNA primer nucleus. If replication of the DNA does not occur, the cell protein. Modified mRNA binds to the 3′ end of the leading strand. Primers are grows to a certain size and thereafter remains at that generated by the enzyme DNA primase and always bind size. 5’ cap – 7-methylguanosine cap as the starting point for DNA replication. Conversely, use of the chemical colchicine makes it possible Poly (A) tail at 3’ to prevent formation of the mitotic spindle and therefore Protects mRNA degredation by exonucleases prevent mitosis, even though replication of the DNA continues- cell growth results from increased production of RNA and cell proteins, which, in turn, cause the cell to grow larger  Components for Gene Expression CELL DIFFERENTIATION Transcription - the information stored in a gene's DNA is passed to a similar molecule called RNA (ribonucleic acid) in the cell nucleus. Translation - the second step in getting from a gene to a protein, takes place in the cytoplasm. The mRNA interacts with a specialized complex called a ribosome, which "reads" the sequence of mRNA nucleotides. GROWTH AND DIFFERENTIAL FACTORS TRANSCRIPTION FACTORS GDF1 - mesoderm induction GDF2 - acetylcholine, iron metabolism (hepcidin) GDF3 - bone ossification, thymus, spleen, bone marrow brain, and adipose tissue of adults GDF5 - expressed in the CNS, survival of neurons that respond to a neurotransmitter (dopamine) GDF6 - bone morphogenetic proteins, ectoderm patterning and eye development GDF8 - myostatin, muscle tissue GDF9 - limited to ovaries, role in ovulation GDF10 - head formation, skeletal morphogenesis GDF11 - expression of Hox genes, olfactory receptors, ganglionic cells in retina GDF15 - regulates apoptotic pathways and inflammation