The School of Biomedical Sciences Wiki - User contributions [en]

Promoters

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The DNA region or sequence that helps in initiating transciption is known as the promoter. Rna polymerase binds to the promoter and further initiates transcription of a gene. They can be present close to the transcription start site or many kilobases away.  Based on their location they can be characterised as Core/Basal promoter elements or the Regulatory region elements. 

Core/Basal elements include TATA boxes and Initiator Sequences (Inr). CpG islands are also present in mammals. Regulatory region elements include UAS/enhancer elements and URS/silencer elements. Other promoters are Downstream Promoter elements (DPE) and BRE (TFIIB recognition element).

Initiation factor

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Initiation factors are proteins that enhance the binding affinity of the various [[Translation|translational]] components.

=== Types of Initiation factors in ''E. coli'' ===

IF1 

IF2 

IF3 

=== Role of Initiation factors ===

IF1 - Stabilizes 30S subunit 

IF2 - Binds f-met-tRNA to 30S-mRNA complex ;  binds to GTP and stimulates [[Hydrolysis|hydrolysis ]]

IF3 - Binds 30S subunit to mRNA ; dissociates monosomes into subunits following [[termination|termination]]<ref>William S. Klug, Michael R. Cummings, Charlotte Spencer, Michael Palladino (2014). Concepts of Genetics Tenth Edition</ref> 

=== References ===

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Erythrocyte

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Erythrocytes (or red blood cell) are one of the main components in the [[Blood|blood ]]along with [[Leukocytes|leukocytes]], [[Platelets|platelets]] and [[Blood plasma|plasma]]. Every second, 2-3 million red blood cells are created<ref name="Blood Groups and Red Cell Antigens">Blood Groups and Red Cell Antigens, Dean.L., -http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=rbcantigen</ref>. These are made from the [[Haemopoetic pluripotent stem cells|haemopoetic pluripotent stem cells]] in the [[Bone marrow|bone marrow]].

They are involved in the transport of [[Oxygen|oxygen]] around the body through the binding of oxygen to the red pigment [[Haemoglobin|haemoglobin]].

=== Structure ===

Erythrocytes contain no [[Nucleus|nucleus]] or [[Mitochondria|mitochondria]], which gives the cell more space so that it can contain more [[Haemoglobin|haemoglobin]]. The more haemoglobin present in the cells, the more [[Oxygen|oxygen]] each red blood cell is able to transport, therefore erythrocytes are able to carry out their function more effectively.

The lack of nuclei or mitochondria gives mature red blood cells their biconcave disc shape, which gives the cell a higher surface area to volume ratio, aiding [[Diffusion|diffusion]] and increasing the cell's ability to absorb oxygen. More oxygen is, therefore, able to diffuse into the cell at any one time.

=== Blood Types ===

Red blood cells also have a role in determining [[Blood types|blood types]]. There are four main blood groups: A, B, O and AB. These are caused by different [[Antigen|antigens]] and different sugars attached to the surface of the erythrocyte.

A blood group contains [[N-acetyl-galactosamine|N-acetyl-galactosamine]] whilst B blood group contains just galactosamine.

=== References ===

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Dementia

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Dementia is a condition associated with an on-going decline in the brain and its abilities; it can lead to having problems with memory loss, thinking speed, understanding, judgement and language. It is an umbrella term for different conditions that involve a decline in cognitive abilities that interfere with daily life<ref>http://www.nhs.uk/conditions/dementia-guide/pages/ about-dementia.aspx</ref>. There are currently around 800,000 people in the UK with dementia and one in three people over 65 will develop dementia; with current estimations that by 2025, dementia sufferers in the UK will reach one million<ref>Alzheimer's Society. Dementia 2014 report statistics. cited [4/12/16] Available from: https://www.alzheimers.org.uk/statistics</ref>.

[[Alzheimer's_disease|Alzheimer’s disease]], [[lewy bodies|Lewy Bodies]], Vascular Dementia and Frontotemporal are the most common types of dementia. Less common variants can include: [[Parkinson's Disease|Parkinson's disease]], [[Creutzfeuldt-Jakob disease|Creutzfeldt-Jakob disease]], [[Huntington's disease|Huntington's disease]] and various others. With [[Alzheimer's disease|Alzheimer’s disease]] being the most common variant, with about sixty-two percent of UK dementia sufferers having this form of condition<ref>http://www.nhs.uk/conditions/dementia-guide/pages/ about-dementia.aspx</ref>. Early onset dementia is another key variant, where dementia-like symptoms can be diagnosed at a generally accepted early age. With most early-onset cases showing symptoms of Dementia between the ages of forty to fifty years old<ref>https://www.alzheimers.org.uk/site/scripts/documents_info.php?documentID=164</ref>.

=== Symptoms ===

The key symptoms of dementia can include<ref>http://www.nhs.uk/Conditions/dementia-guide/Pages/symptoms-of-dementia.aspx</ref>:

*Memory loss
*Communication difficulties
*Become apathetic and lose interest in daily activities very quickly
*Orientation problems i.e. becoming lost and forgetting where they live
*Changes in personality and mood
*Depression
*Hallucinations
*Difficulty recognising loved ones

=== Causes ===

Dementia is caused by gradual changes and damage in the [[Brain|brain]]. The most common causes of Dementia involve the brain cells degeneration and hence die more quickly than they would as part of the normal ageing process. The changes usually happen because of a build-up of abnormal [[Proteins|proteins]] in the brain. This damage leads to a decline in a person's mental and sometimes, physical abilities. The abnormal proteins are different and have differing effects in each type of Dementia<ref>NHS Choices. Causes of Dementia. Cited [4/12/16], Available from: http://www.nhs.uk/Conditions/dementia-guide/Pages/causes-of-dementia.aspx</ref>. Causes of conditions involved with Dementia may be genetically linked, as [[Tandem repeat polymorphisms|polymorphisms]] in the [[APP gene|APP gene]] is a significant factor in causing Alzheimer's disease and Huntington's disease is caused by a [[Autosomal Dominant Disorders|autosomonal]] dominant inherited mutation<ref>https://ghr.nlm.nih.gov/gene/APP#conditions</ref>.

=== Treatment ===

At the present moment, there are no drug treatments that can cure the common types of Dementia. However, medicines have been developed which can temporarily alleviate symptoms, or slow down their progression<ref>http://www.nhs.uk/Conditions/dementia-guide/Pages/dementia-cure.aspx</ref>. There are two types of medication used to treat Alzheimer’s disease: [[Acetylcholinesterase|Acetylcholinesterase]] inhibitors and NMDA receptor antagonists. The generic names for the [[Cholinesterase|Cholinesterase]] inhibitors are Doneprezil, Rivastigmine and Galantamine; these can temporarily improve or stabilize memory and thinking skills. A specific type of [[NMDA receptor|NMDA receptor]] agonists called Memantine prevents a decline in learning and memory<ref>Dementia and Healthcare. NHS Booklet.</ref>. There are currently no medications to treat other types including Dementia with Lewy Bodies, Parkinson’s disease, Frontotemporal disorders or Vascular Dementia, yet treatment currently focuses on reducing symptoms by making more people comfortable living with the condition. There are research projects being undertaken that involve treatment using: BACE (B Amyloid Cleaving Enzyme) inhibitor, which stops [[Amyloid|amyloid]] being produced. There are trials involving anti-amyloid treatment, which are [[Immunizins|immunizins]] against amyloid.<ref>NIHR DENDRON Research Questionnaire. DJ. cited [January 2016]</ref>

There are also many alternative psychological treatments being used such as there are increasing numbers of Dementia villages (as found in Hogewey, Netherlands<ref>http://hogeweyk.dementiavillage.com</ref>), dementia cafés and increased awareness of Dementia related conditions. The latter involves promoting the education of the public, through celebrity endorsed advertisements<ref>https://www.youtube.com/watch?v=x9MvEZskR6o</ref> and fundraising events for various Dementia related charities<ref>https://www.alzheimers.org.uk/site/scripts/documents.php?categoryID=200388</ref>.

=== References. ===

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Microvilli

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Microvilli are thin, finger-like projections on the surface of cells and are particularly abundant in [[Epithelial cells|epithelia]], where a large surface area is required for efficient functionality such as absorption. Microvilli increase the surface area of the cell<ref>Lodish et al.(2013)Molecular Cell Biology.United States: Katherine</ref> and can be often found in large numbers. A multitude of microvilli seen in the lining of the small intestine are described as a ''brush border ''due to their 'paintbrush tip' appearance<ref>W J Krause. Krause's essential human histology for medical students, third edition. Boca Raton 2005. p37</ref>.

Each microvilli has about 20-30 parallel [[Actin filaments|actin filaments]] that extend from the tip into the cell cortex. In all the actin filaments the plus ends point away from the cell body and are held together by actin-bundling proteins. The most important of which is villin, a [[Protein|protein]] that is specific to microvilli and cross-links actin filaments into tight bundles.

At the base of each microvillus the actin filaments are anchored into a specialized region known as the terminal web. This contains a concentrated network of spectrin molecules and a layer of [[Intermediate filaments|intermediate filaments]]. It is thought that spectrin imparts rigidity to the cell cortex; because the actin filaments are anchored to the terminal web, this keeps the microvilli orientated perpendicularly to the apical surface of the cell. The [[Actin|actin]] filaments are attached to the [[Plasma membrane|plasma membrane]] by lateral bridges composed of [[Myosin-I|myosin-I]] and several other [[Molecules|molecules]] including the Ca2+<ref>G M. Fuller and D, Shiels. Molecular Basis of Medical Cell Biology (1998) 1st edition. Chapter 7 PP.140-141</ref>.

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Le Chatelier's Principle

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Le Chatelier's Principle states that when a system experiences a disturbance, it will respond in order to restore the [[Equilibrium|equilibrium]] state<ref>Khan Academy. (2017). Le Chatelier's principle. [online] Available at: https://www.khanacademy.org/science/chemistry/chemical-equilibrium/factors-that-affect-chemical-equilibrium/v/le-chatelier-s-principle [Accessed 4 Dec. 2017].</ref>. This means that when one or more factors that affect an equilibrium is changed, the position of equilibrium shifts in the direction that opposes the change. For example, if more reactants are added to an equilibrium system, according to Le Chatelier's Principle, more products will be produced and the equilibrium position is said to be shifted to the right until the equilibrium is resotred. 

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Resting membrane potential

2017-12-05T10:43:24Z

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The resting membrane potential of a neurone is the electrical potential, or voltage, across the [[Plasma_membrane|plasma membrane]] of an unstimulated nerve cell. <ref>Jeff Hardin, Gregory Bertoni, Lewis J. Kleinsmith. Becker's World of the Cell, Eighth edition. p G-20.</ref>  It occurs when the net flow of [[Ions|ions]] across the [[Plasma membrane|plasma membrane]] equals zero. In humans this is said to be around -70mV<ref>Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P. (2008) Molecular Biology of the Cell, 5th edition, New York: Garland Science (page 669)</ref>.  This means that the inside of the cell is negatively charged in comparison to the outside.

Resting membrane potentials are maintained by two different types of ion channels: the [[Sodium-potassium pump|sodium-potassium pump]] and the [[Sodium and potassium leak channels|sodium and potassium leak channels]]. Firstly, there is a higher concentration of the potassium ions inside the cell in comparison to the outside of the cell. This creates an unequal distribution of potassium ions, or more accurately, a potassium ion gradient is created. Therefore, following the concentration gradient, the potassium ions will diffuse from the inside of the cell to outside of the cell via its leaky channels. As the potassium ions leave the cell, it increases the number of anions trapped inside the cell, hence accumulating the negative charges and the positive charges are accumulated outside of the cell. Therefore more positively charged ions are being removed from the cell than are entering it making the inside environment of the cell comparatively negative to the outside.<ref>Jeff Hardin, Gregory Bertoni, Lewis J. Kleinsmith. Becker's World of the Cell. p.368-369</ref>

The sodium-potassium pump moves three sodium ions out of the cell for every two potassium ions it moves into the cell continuously. It therefore maintains the large potassium ion gradient across the membrane, which in turn providing the basis for resting membrane potential. The negatively charged macromolecules or ions, usually chloride ions , cannot pass through the plasma membrane as they are too large to be moved in or out of the cell via the chloride channels. This is due to the channels being too large and bulky, hence[[Anions| anions]] remain trapped inside the cell<ref>Khan Academy. The Neurone and Nervous System. The Membrane Potential. How ions cross the membrane. [Online]. Available at: https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/the-membrane-potential</ref>.

The resting membrane potential can be measured by placing one microelectrode inside the cell and another outside the cell. The values are generated in millivolts (mV). The ratios of the negative charges and positive charges between inside and outside of the cells are compared.<ref>Jeff Hardin, Gregory Bertoni, Lewis J. Kleinsmith. Becker's World of the Cell. p367</ref>

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Spinal chord

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The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the [[Medulla oblongata|medulla oblongata]] in the [[Brainstem|brainstem]] to the lumbar region of the vertebral column. The brain and spinal cord together make up the central nervous system (CNS).

The spinal cord starts at the medulla oblongata of the brainstem and ends at the lumbar area of the vertebral column. The spinal cord as well as the brain make up the [[Central nervous system|central nervous system]] (CNS).

Three tissue layers known as [[meninges|meninges]] surround and protect the [[Brain|brain]] and spinal cord. The outermost protective layer is called the [[dura mater|dura mater]]. The epidural space, which is made up of a network of blood vessels as well as adipose tissue, occurs between the surrounding vertebrate bone and the dura mater. The middle protective layer resembles spider webs and therefore is known as the [[arachnoid mater|arachnoid mater]]. The subarachnoid space contains [[cerebrospinal fluid|cerebrospinal fluid]], and lies in between the pia and arachnoid mater. The pia mater is the delicate, innermost  protective layer<ref>http://vanat.cvm.umn.edu/neurLab2/index.html</ref>.

The human spine has 31 segments which include: 

*8 cervical segments
*12 thoracic segments
*5 lumbar segments
*5 sacral segments 
*1 cocygeal segment 

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XYY Syndrome

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XYY syndrome, also known as 47,XXY syndrome affects males and is defined by an extra copy of the [[Y-chromosome|Y-chromosome]] <ref>Genetics Home Reference. (2014). 47,XYY Syndrome. Available: http://ghr.nlm.nih.gov/condition/47xyy-syndrome. Last accessed 25th Nov 2014.</ref>  This syndrome is usually a result of random [[Nondisjunction|nondisjunction]] during [[Meiosis II|meiosis II]] of [[Spermatogenesis|spermatogenesis]] which results in [[Sperm_cell|sperm cells]] with an additional Y-chromosome <ref>National Genetics and Genomicsc Education Centre (NHS). (2013). 47, XYY. Available: http://www.geneticseducation.nhs.uk/genetic-conditions-54/632-47-xyy-new. Last accessed 26th Nov 2014.</ref>. Most of the cases of this sydrome therefore are not inherited. Children with this syndrome appear normal with no medical problems or illnesses.Their intellectual ability is considered to be normal even though they have a need for learning support. They also are very vulnerable to stress along with behaviour problems<ref>Rare Chromosome Disorder Support Group. (2005). Unique XYY. Available: http://www.rarechromo.org/information/Chromosome_Y/XYY%20FTNW.pdf. Last accessed 26th Nov 2014.</ref>. 

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Cancer

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[[Image:Age specific incidence.gif|right|age specific incidence of cancer in 30-80 year old individuals]][[Image:Japan.gif|right|fig 3. incidence of cancer between different ethnic backgrounds]][[Image:Agr.gif|right|fig 2. Childhood incidence of cancer]] Cancer is an uncontrolled proliferation of [[Cell|cells]] inside the body. These cells have an abnormal [[Mitosis|mitotic]] cycle causing them to grow uncontrollably, leading to [[tumour|tumours]], and thus a [[Disease|disease]] state. Hanahan and Weinberg's [http://www.ncbi.nlm.nih.gov/pubmed/21376230 Hallmarks of Cancer] is a much-cited paper that is useful for defining cancer and understanding the six traits that many different cancer types have in common<ref>Hanahan D, Weinberg RA, 'Hallmarks of Cancer: The Next Generation' Cell 144 p646-674, Cell. Available at http://www.cell.com/cell/abstract/S0092-8674(11)00127-9 Last accessed on 24 October 2014.</ref>. The study and treatment of cancer is known as [[oncology|oncology]].

=== Causal factors ===

There are many different forms of cancer associated with every [[Organ|organ]] in the body from the extremely rare (heart cancer) to the four most common cancers ([[Prostate|prostate]], [[Lungs|lung]], [[Breast Cancer|breast]] (women) and [[Colon|colon]]). The causal factors in cancer vary wildly from [[Gene|genetic]] predisposition to environmental [[Carcinogen|carcinogens]] with the exact makeup of these carcinogens is highly disputed, but some are widely accepted as cancer-causing. Radiation, environmental toxins, [[UV|UV]], [[Obesity|obesity]], [[Virus|viruses]] and chemical carcinogens such as [[Benzene|benzene]]. Equally, cancers can be very age-specific such as [[Retinoblastoma|retinoblastoma]], which tends to affect the very young. [[testicular cancer|Testicular cancer]] which tends to affect the 16-25-year-old categories and [[prostate cancer|prostate cancer]] which is a very common in the 60-80-year-old category (fig 1 and 2)<ref>Dynamics of Cancer: Incidence, Inheritance, and Evolution.Frank SA.Princeton (NJ): Princeton University Press; 2007. chapter 2, fig 2.2</ref><ref>Dynamics of Cancer: Incidence, Inheritance, and Evolution.Frank SA.Princeton (NJ): Princeton University Press; 2007. chapter 2, fig 2.4</ref>. Genetically predisposed individuals will often develop cancer more severely and often earlier in life. Whereas people from different ethnic backgrounds can have very different cancer incidence curves. This is due to differential genetics between populations and the lifestyles changes that can be seen between countries (fig 3)<ref>Dynamics of Cancer: Incidence, Inheritance, and Evolution.Frank SA.Princeton (NJ): Princeton University Press; 2007. chapter 2, fig 2.21</ref>. The Japanese populous have higher rates of colon and [[Lung|lung]] cancer compared to England in the ~ 30 – 70 age category but by 80 England has nearly caught the rate up. So as you can see there are many factors and differentials related to cancer and its incidence. Old age cancers can strike in the prime of life and childhood cancers can develop late. It is a worldwide issue of great importance and will continue to be far into the future.

=== Treatment of Cancer ===

The treatment of cancer had developed greatly over the last few years. Firstly, there are some screening techniques used to catch cancer before it has time to properly develop. These include [[Mammography|mammography]] to screen for [[Breast_Cancer|breast cancer]] as well as smear tests to screen for [[cervical cancer|cervical cancer]]<ref>Roger J. King, Mike W. Robins (2006). Cancer Biology. 3rd ed. Essex: Pearson. p230-62.</ref>. In the UK at this time, these techniques are given as standard to women over a certain age, smear tests are given out to women once they reach the age of 25. In the majority of cancer cases however the patient detects the symptoms and will then relay these to a doctor who can make a [[Diagnosis|diagnosis]]<ref>Roger J. King, Mike W. Robins (2006). Cancer Biology. 3rd ed. Essex: Pearson. p230-62.</ref>. The three main areas of cancer are [[Surgery|surgery]], [[Chemotherapy|chemotherapy]] and [[Radiotheraphy|radiotheraphy]]. Depending on the type and severity of cancer depend on which of these are used and often a combination of all of them are required<ref>Roger J. King, Mike W. Robins (2006). Cancer Biology. 3rd ed. Essex: Pearson. p230-62.</ref>.

Surgery is one of the main treatments for cancer. It might be the only treatment you need. It is a local treatment – it only treats the part of the body operated on. So it may cure cancer that is completely contained in one area and hasn't spread. Usually, the earlier a cancer is found the easier it is to remove it<ref name="null">8 Cancer Research UK, Last updated 4, April 2016, available at http://www.cancerresearchuk.org/about-cancer/cancers-in-general/treatment/surgery/surgery-to-treat-cancer#ZHp2XowRyqpib6lm.99References</ref>.

When cancer has progressed and surgery cannot be completed, [[Chemotherapy|chemotherapy]] and [[Radiotherapy|radiotherapy]] are the main opportunities for treating cancer. However, treatment with chemotherapy and radiotherapy is damaging for healthy cells too. Thus, the [[Page doesn't exist|targeted anti-cancer drugs]] are promising in cancer treatment, these drugs target only cancer cells<ref name="Uwe Marc Martens. Small Molecules in Oncology. 2nd Ed., Berlin: Springer. 2014">Uwe Marc Martens. Small Molecules in Oncology. 2nd Ed., Berlin: Springer. 2014</ref>. For instance, cancer cells distinguish by an active action of [[Protein kinases|protein kinases]]. Thus, targeting kinases is advantageous<ref>Claudio Raimondi, Veronique Calleja, Riccardo Ferro, Alessandro Fantin, Andrew M.Riley, Barry V.L. Potter, Caroline H. Brennan, Tania Maffuci, Banafshe Larijani, Marco Falasca. A Small Molecule Inhibitor of PDK/PLCγ1 Interaction Blocks Breast and Melanoma Cancer Cell Invasion. Scientific Reports 2016; 6, 1:1-14</ref>.

Many treatments, however, can come with side effects. For example, Chemotherapy can result in the patient feeling fatigue, [[nausea|nausea]] and hair loss (although there is a cold cap which can be used to prevent hair loss, this can only be used with certain cancers)<ref>http://www.nhs.uk/Conditions/Chemotherapy/Pages/Side-effects.aspx</ref>. Radiotherapy can result in sore skin, tiredness and loss of appetite and surgery can come with its own problems and complications, including infection.

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Talk:Cell differentiation

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Cell differentiation

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During development, precursor cells can become more specialized by cellular differentiation. The newly synthesized cells therefore can develop into one cell type or another. A single cell can differentiate to function as a [[Neurone|neurone]] or a [[Epithelial_Cells|epithelial cell]]. In multicelluar organisms, cell differentiation occurs multiple times to form complex system of tissues with specific functions. This process is seen during embryonic development, renewal of tissues, regeneration of missing tissues and cells, etc. [[Totipotent_stem_cells|Totipotent cells]] are the only cells that can differentiate into any cell type.

Talk:Cell differentiation

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During development, precursor cells can become more specialized by cellular differentiation. The newly synthesized cells therefore can develop into one cell type or another. A single cell can differentiate to function as a [[Neurone|neuron]] or a [[Epithelial cell|epithelial cell]]. In multicelluar organisms, cell differentiation occurs multiple times to form complex system of tissues with specific functions. This process is seen during embryonic development, renewal of tissues, regeneration of missing tissues and cells, etc. [[Totipotent stem cells|Totipotent cells]] are the only cells that can differentiate into any cell type.