NO ES MÁGIA SOLO ES FÍSICA!! (contracción y expansión térmica del aire)

Experimento

Analizar la contracción y la expansión térmica del aire

Materiales:

*un huevo cocido sin cascara
*un frasco con un diámetro poco menor que el del huevo
*Dos recipientes resistentes al calor
*Dos litros de agua
*hielo


 Procedimiento :

♥hervir un litro de agua

♥ponemos hielo en uno de los recipientes y luego le ponemos agua

♥ ponemos el huevo en la entrada del frasco.Observemos que no se cae

Después

♥Ponemos el frasco en el recipiente con agua y hielo ,el huevo se hunde

♥Ahora ponemos el recipiente con agua caliente, el huevo asciende


☺Conclusión:

la presión de una cantidad fija de gas, es inversamente proposicional al volumen que ocupa, siempre y cuando se mantenga la temperatura  constante

tenemos en claro que: a volumen constante con un aumento de temperatura de un gas ideal se corresponde inmediatamente con un aumento de la presión y viceversa

experiment

To analyze the thermal expansion and contraction of air

materials:

* a peeled boiled egg
* a jar with a diameter slightly smaller than the egg
* Two heat resistant containers
* Two liters of water
* ice



  procedure:

♥ boil a liter of water

♥ put ice in one of the containers and then put water

♥ put the egg in the input that does not fall frasco.Observemos

after

♥ We put the bottle in the container with water and ice, the egg sinks

♥ Now we put the container with hot water, the egg rises


☺ Conclusion:

the pressure of a fixed amount of gas is inversely propositional to the volume it occupies, as long as the temperature is maintained constant

have made clear that: at constant volume with increasing temperature of an ideal gas immediately corresponds with an increase in pressure and vice versa

Clonación 

La clonación (del griego κλών, "retoño, rama") puede definirse como el proceso por el que se consiguen, de forma asexual, copias semejantes de un organismo, célula omolécula ya desarrollado.

Se deben tomar en cuenta las siguientes características

• En primer lugar se necesita clonar las moléculas, ya que no se puede hacer un órgano o parte del "clon" si no se cuenta con las moléculas que forman a dicho ser.
• Ser parte de un animal ya "desarrollado", porque la clonación responde a un interés por obtener copias de un determinado animal que nos interesa, y sólo cuando es adulto conocemos sus características.
• Por otro lado, se trata de crearlo de forma asexual. La reproducción sexual no nos permite obtener copias idénticas, ya que este tipo de reproducción por su misma naturaleza genera diversidad.

Clonación molecular

La clonación molecular se utiliza en una amplia variedad de experimentos biológicos y las aplicaciones prácticas van desde la toma de huellas dactilares a producción de proteínasa gran escala.

En la práctica, con el fin de amplificar cualquier secuencia en un organismo vivo, la secuencia a clonar tiene que estar vinculada a un origen de replicación; que es una secuencia de ADN.

Transfección

Se introduce la secuencia formada dentro de células.

Selección

Finalmente se seleccionan las células que han sido transfectadas con éxito con el nuevo ADN.

Inicialmente, el ADN de interés necesita ser aislado de un segmento de ADN de tamaño adecuado. Posteriormente, se da el proceso de ligación cuando el fragmento amplificado se inserta en un vector de clonación: El vector se linealiza (ya que es circular),usando enzimas de restricción y a continuación se incuban en condiciones adecuadas el fragmento de ADN de interés y el vector con la enzima ADN ligasa.

Tras la ligación del vector con el inserto de interés, se produce la transfección dentro de las células, para ello las células transfectadas son cultivadas; este proceso, es el proceso determinante, ya que es la parte en la que vemos si las células han sido transfectadas exitosamente o no.

Tendremos que identificar por tanto las células transfectadas y las no transfectadas, existen vectores de clonación modernos que incluyen marcadores de resitencia a losantibióticos con los que sólo las células que han sido transfectadas pueden crecer. Hay otros vectores de clonación que proporcionan color azul/ blanco cribado. De modo, que la investigación de las colonias es necesaria para confirmar que la clonación se ha realizado correctamente.

Clonación celular

Clonar una célula consiste en formar un grupo de ellas a partir de una sola. En el caso de organismos unicelulares como bacterias y levaduras, este proceso es muy sencillo, y sólo requiere la inoculación de los productos adecuados.

Sin embargo, en el caso de cultivos de células en organismos multicelulares, la clonación de las células es una tarea difícil, ya que estas células necesitan unas condiciones del medio muy específicas.

Una técnica útil de cultivo de tejidos utilizada para clonar distintos linajes de células es el uso de aros de clonación (cilindros).

De acuerdo con esta técnica, una agrupación de células unicelulares que han sido expuestas a un agente mutagénico o a un medicamento utilizado para propiciar la selección se ponen en una alta dilución para crear colonias aisladas; cada una proviniendo de una sola célula potencialmente y clónicamente diferenciada.

En una primera etapa de crecimiento, cuando las colonias tienen sólo unas pocas células; se sumergen aros estériles de poliestireno en grasa, y se ponen sobre una colonia individual junto con una pequeña cantidad de tripsina.

Las células que se clonan, se recolectan dentro del aro y se llevan a un nuevo contenedor para que continúe su crecimiento en forma natural.

Clonación de organismos de forma natural

La clonación de un organismo es crear un nuevo organismo con la misma información genética que una célula existente. Es un método de reproducción asexual, donde lafertilización no ocurre. En términos generales, sólo hay un progenitor involucrado. Esta forma de reproducción es muy común en organismos como las amebas y otros seres unicelulares, aunque la mayoría de las plantas y hongos también se reproducen asexualmente.

También se incluye la obtención de gemelos idénticos de manera natural. Se considera como una alteración espontánea durante el desarrollo embrionario, ignorándose su causa, aunque existe una correlación familiar estadísticamente significativa.

Consideraciones éticas a la clonación

Argumentos en favor de la clonación humana terapéutica

El aumento de la esperanza de vida de los seres humanos ha provocado un notable aumento de las enfermedades crónicas o degenerativas, como las enfermedades cardíacas, elalzheimer o el cáncer. El principal problema es que estas enfermedades afectan a partes del organismo que, debido a un aumento de la longevidad o al daño irreversible sufrido, el cuerpo no puede regenerar por sí solo. Una solución a estas enfermedades puede ser la clonación terapéutica, al ser una especialización del tratamiento con células madre. Cuando un órgano o tejido ha sido dañado es necesario regenerarlo o realizar un trasplante, pero los trasplantes tienen varias dificultades, como la dificultad para encontrar donantes, el posible rechazo inmunitario o la imposibilidad de trasplantar ciertos tejidos u órganos.

La clonación terapéutica ofrece grandes posibilidades, aún en investigación, para aplicarse en sustitución a los trasplantes u otras terapias poco efectivas contra enfermedades graves. La obtención de células embrionarias de un individuo, para utilizarlas en beneficio de su propia salud, supone una posibilidad de curación que es tomada en consideración, por el derecho a la salud que tienen los seres humanos, según la Organización Mundial de la Salud.

Cloning

loning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments (molecular cloning), cells (cell cloning), or organisms. The term also refers to the production of multiple copies of a product such as digital media or software.

The term clone is derived from the Ancient Greek word κλών (klōn, “twig”), referring to the process whereby a new plant can be created from a twig. In horticulture, the spelling clon was used until the twentieth century; the final e came into use to indicate the vowel is a "long o" instead of a "short o". Since the term entered the popular lexicon in a more general context, the spelling clone has been used exclusively.

In botany, the term lusus was traditionally used.^]

In the United States, the human consumption of meat and other products from cloned animals was approved by the FDA on December 28, 2006, with no special labeling required. Cloned beef and other products have since been regularly consumed in the US without distinction. Such practice has met strong resistance in other regions, such as Europe, particularly over the labeling issue.

Molecular cloning refers to the process of making multiple molecules. Cloning is commonly used to amplify DNA fragments containing whole genes, but it can also be used to amplify any DNA sequence such as promoters, non-coding sequences and randomly fragmented DNA. It is used in a wide array of biological experiments and practical applications ranging from genetic fingerprinting to large scale protein production. Occasionally, the term cloning is misleadingly used to refer to the identification of the chromosomal location of a gene associated with a particular phenotype of interest, such as in positional cloning. In practice, localization of the gene to a chromosome or genomic region does not necessarily enable one to isolate or amplify the relevant genomic sequence. To amplify any DNA sequence in a living organism, that sequence must be linked to an origin of replication, which is a sequence of DNA capable of directing the propagation of itself and any linked sequence. However, a number of other features are needed and a variety of specialised cloning vectors (small piece of DNA into which a foreign DNA fragment can be inserted) exist that allow protein expression, tagging, single stranded RNA and DNA production and a host of other manipulations.

Cloning of any DNA fragment essentially involves four steps

1. fragmentation - breaking apart a strand of DNA
2. ligation - gluing together pieces of DNA in a desired sequence
3. transfection - inserting the newly formed pieces of DNA into cells
4. screening/selection - selecting out the cells that were successfully transfected with the new DNA

Although these steps are invariable among cloning procedures a number of alternative routes can be selected, these are summarized as a 'cloning strategy'.

Initially, the DNA of interest needs to be isolated to provide a DNA segment of suitable size. Subsequently, a ligation procedure is used where the amplified fragment is inserted into a vector (piece of DNA). The vector (which is frequently circular) is linearised using restriction enzymes, and incubated with the fragment of interest under appropriate conditions with an enzyme called DNA ligase. Following ligation the vector with the insert of interest is transfected into cells. A number of alternative techniques are available, such as chemical sensitivation of cells, electroporation, optical injection and biolistics. Finally, the transfected cells are cultured. As the aforementioned procedures are of particularly low efficiency, there is a need to identify the cells that have been successfully transfected with the vector construct containing the desired insertion sequence in the required orientation. Modern cloning vectors include selectable antibiotic resistance markers, which allow only cells in which the vector has been transfected, to grow. Additionally, the cloning vectors may contain colour selection markers, which provide blue/white screening (alpha-factor complementation) on X-gal medium. Nevertheless, these selection steps do not absolutely guarantee that the DNA insert is present in the cells obtained. Further investigation of the resulting colonies must be required to confirm that cloning was successful. This may be accomplished by means of PCR, restriction fragment analysis and/or DNA sequencing.

Cellular cloning

Unicellular organisms

Cloning a cell means to derive a population of cells from a single cell. In the case of unicellular organisms such as bacteria and yeast, this process is remarkably simple and essentially only requires the inoculation of the appropriate medium. However, in the case of cell cultures from multi-cellular organisms, cell cloning is an arduous task as these cells will not readily grow in standard media.

A useful tissue culture technique used to clone distinct lineages of cell lines involves the use of cloning rings (cylinders). According to this technique, a single-cell suspension of cells that have been exposed to a mutagenic agent or drug used to drive selection is plated at high dilution to create isolated colonies; each arising from a single and potentially clonal distinct cell. At an early growth stage when colonies consist of only a few of cells, sterile polystyrene rings (cloning rings), which have been dipped in grease are placed over an individual colony and a small amount of trypsin is added. Cloned cells are collected from inside the ring and transferred to a new vessel for further growth.

Cloning in stem cell research

Somatic cell nuclear transfer, known as SCNT, can also be used to create embryos for research or therapeutic purposes. The most likely purpose for this is to produce embryos for use in stem cell research. This process is also called "research cloning" or "therapeutic cloning." The goal is not to create cloned human beings (called "reproductive cloning"), but rather to harvest stem cells that can be used to study human development and to potentially treat disease. While a clonal human blastocyst has been created, stem cell lines are yet to be isolated from a clonal source.

Therapeutic cloning is achieved by creating embryonic stem cells in the hopes of treating diseases such as diabetes and Alzheimer’s. The process begins by taking out the nucleus that contains the DNA from an egg and putting it in a nucleus from an adult. In the case of someone with Alzheimer’s disease, the nucleus from a skin cell of that patient is placed into an empty egg. The reprogrammed cell begins to develop into an embryo because the egg reacts with the transferred nucleus. The embryo will become genetically identical to the patient. The embryo will then form a blastocyst which has the potential to form/become any cell in the body.

The reason why SCNT is used for cloning is because somatic cells can be easily acquired and cultured in the lab. This process can either add or delete specific genomes of farm animals. A key point to remember is that cloning is achieved when the oocyte maintains its normal functions and instead of using sperm and egg genomes to replicate, the oocyte is inserted into the donor’s somatic cell nucleus. The oocyte will react on the somatic cell nucleus, the same way it would on sperm cells.

SCNT Process The process of cloning a particular farm animal using SCNT is relatively the same for all animals. The first step is to collect the somatic cells from the animal that will be cloned. The somatic cells could be used immediately or stored in the laboratory for later use.The hardest part of SCNT is removing maternal DNA from an oocyte at metaphase II. Once this has been done, the somatic nucleus can be inserted into an egg cytoplasm. This creates a one-cell embryo. The grouped somatic cell and egg cytoplasm are then introduced to an electrical current. This energy will hopefully allow the cloned embryo to begin development. The successfully developed embryos are then placed in surrogate recipients, such as a cow or sheep in the case of farm animals.

Applications of SCNT SCNT is seen to be a great method for producing agriculture animals for food consumption. It successfully cloned sheep, cattle, goats, and pigs. Another benefit is SCNT is seen as a solution to clone endangered species that are on the verge of going extinct.

Limitations of SCNT Stresses placed on both the egg cell and the introduced nucleus are enormous, leading to a high loss in resulting cells. For example, Dolly the sheep was born after 277 eggs were used for SCNT, which created 29 viable embryos. Only three of these embryos survived until birth, and only one survived to adulthood. As the procedure currently cannot be automated, but has to be performed manually under a microscope, SCNT is very resource intensive. The biochemistry involved in reprogramming thedifferentiated somatic cell nucleus and activating the recipient egg is also far from understood.

In SCNT, not all of the donor cell's genetic information is transferred, as the donor cell's mitochondria that contain their own mitochondrial DNA are left behind. The resulting hybrid cells retain those mitochondrial structures which originally belonged to the egg. As a consequence, clones such as Dolly that are born from SCNT are not perfect copies of the donor of the nucleus.

Human cloning

Human cloning is the creation of a genetically identical copy of an existing or previously existing human. The term is generally used to refer to artificial human cloning; human clones in the form of identical twins are commonplace, with their cloning occurring during the natural process of reproduction. There are two commonly discussed types of human cloning: therapeutic cloning and reproductive cloning. Therapeutic cloning involves cloning adult cells for use in medicine and is an active area of research. Reproductive cloning would involve making cloned humans. A third type of cloning called replacement cloning is a theoretical possibility, and would be a combination of therapeutic and reproductive cloning. Replacement cloning would entail the replacement of an extensively damaged, failed, or failing body through cloning followed by whole or partial brain transplant.

The various forms of human cloning are controversial. There have been numerous demands for all progress in the human cloning field to be halted. Most scientific, governmental and religious organizations oppose reproductive cloning. The American Association for the Advancement of Science (AAAS) and other scientific organizations have made public statements suggesting that human reproductive cloning be banned until safety issues are resolved. Serious ethical concerns have been raised by the future possibility of harvesting organs from clones. Some people have considered the idea of growing organs separately from a human organism - in doing this, a new organ supply could be established without the moral implications of harvesting them from humans. Research is also being done on the idea of growing organs that are biologically acceptable to the human body inside of other organisms, such as pigs or cows, then transplanting them to humans, a form of xenotransplantation.

The first hybrid human clone was created in November 1998, by Advanced Cell Technologies. It was created from a man's leg cell, and a cow's egg whose DNA was removed. It was destroyed after 12 days. Since a normal embryo implants at 14 days, Dr Robert Lanza, ACT's director of tissue engineering, told the Daily Mail newspaper that the embryo could not be seen as a person before 14 days. While making an embryo, which may have resulted in a complete human had it been allowed to come to term, according to ACT: "[ACT's] aim was 'therapeutic cloning' not 'reproductive cloning'"

On January, 2008, Wood and Andrew French, Stemagen's chief scientific officer in California, announced that they successfully created the first 5 mature human embryos usingDNA from adult skin cells, aiming to provide a source of viable embryonic stem cells. Dr. Samuel Wood and a colleague donated skin cells, and DNA from those cells was transferred to human eggs. It is not clear if the embryos produced would have been capable of further development, but Dr. Wood stated that if that were possible, using the technology for reproductive cloning would be both unethical and illegal. The 5 cloned embryos, created in Stemagen Corporation lab, in La Jolla, were destroyed.

Herencia genética

La herencia genética es la manera en que se transmiten, de generación en generación, las características fisiológicas, morfológicas y bioquímicas de los seres vivos bajo diferentes condiciones ambientales.

Introducción

La herencia genética sólo representa una parte de la herencia, es decir, el porcentaje de la variabilidad fenotípica debido a efectos genéticos aditivos. Pero definir las fuentes y el origen de las semejanzas entre miembros de una misma familia incluye también otro tipo de variables. El estudio de la herencia cuantifica la magnitud de la semejanza entre los familiares y representa el porcentaje de variación que se debe a todos los efectos aditivos familiares, incluyendo la epidemiología genética aditiva y los efectos del medio ambiente. En los casos en que los miembros de una misma familia conviven resulta imposible discriminar las variables genéticas fenotípicas de las del entorno y medioambiente. Los estudios de mellizos separados al nacer y de hijos adoptivos permiten realizar estudios epidemiológicos separando los efectos hereditarios entre los de origen genético y las etiologías más complejas, incluyendo las interacciones entre los individuos y la educación. Además, diversos factores influyen al momento de interpretar los estudios de la herencia incluyendo los supuestos previos por parte de los investigadores. 

Uno de los debates entre los científicos es cual es el peso de la naturaleza y cual es el peso de la cultura, es decir, la magnitud de la influencia de los genes versus la magnitud de la educación y el medioambiente.³ El dilema de una oposición entre naturaleza y cultura, lo innato versus lo adquirido, es decir innato o adquirido, frase acuñada por Francis Galtonen el siglo XIX.

Está comprobado que en los genes se transmite el color de la piel, del cabello, de los ojos. ¿Se transmite también algo de la personalidad, los gustos, el carácter, las capacidades o la inteligencia?

La doctora en neurobiología Catherine Vidal, directora de investigación en el Instituto Pasteur en París, refiriéndose al determinismo genético, sostiene que la estructura mental no es inmutable, ya que la plasticidad cerebral hace que continuamente aparezcan nuevos circuitos neuronales basados en la experiencia y en el aprendizaje, por lo que, a nivel cerebral, nada es fijo o programado desde el nacimiento. Nacemos con sólo el 10% de los 100 mil millones de neuronas ya interconectadas. El 90% de las conexiones restantes se construirá progresivamente a lo largo de nuestra vida en función de las influencias de la familia, la educación, la cultura, la sociedad y el medio ambiente.⁴

El doctor Albert Rothenberg, profesor de psiquiatría en la Universidad de Harvard y la doctora Grace Wyshak, profesora de psiquiatría en la misma universidad, estudiaron el árbol genealógico 435 de los 488 químicos, físicos, médicos y fisiólogos galardonados con el Premio Nobel entre 1901 y 2003, y el de 50 escritores ganadores del Premio Nobel de literatura y 135 ganadores del Premio Pulitzer. Los resultados de sus investigaciones contradicen la teoría de la transmisión directa del genio del británico Francis Galton publicada en el libro «Hereditary Genius». Según Albert Rothenberg y Grace Wyshak la genialidad no depende de los genes sino de una constelación de factores que no son genéticos sino psicológicos. Los procesos afectivos y cognitivos involucrados en la creatividad son el resultado de una combinatoria de educación, genética y factores sociales. Los premiados no llevaban la genialidad grabada en el ADN ni provenían de familias con coeficientes intelectuales privilegiados sino que se habían educado con el incentivo y la orientación creativa de sus padres. Los deseos incumplidos de estos padres buscaban realizarse a través de sus hijos.

Heredity

Heredity is the passing of traits to offspring (from its parent or ancestors). This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause somespecies to evolve. The study of heredity in biology is called genetics, which includes the field of epigenetics.

Overview

In humans, eye color is an inherited characteristic and an individual might inherit the "brown-eye trait" from one of the parents. Inherited traits are controlled by genes and the complete set of genes within an organism's genome is called itsgenotype.

The complete set of observable traits that make the structure and behavior of an organism is called its phenotype. These traits come from the interaction of its genotype with the environment. As a result, many aspects of an organism's phenotype are not inherited. For example, suntanned skin comes from the interaction between a person's genotype and sunlight; thus, suntans are not passed on to people's children. However, some people tan more easily than others, due to differences in their genotype; a striking example are people with the inherited trait of albinism, who do not tan at all and are very sensitive to sunburn.

Heritable traits are known to be passed from one generation to the next via DNA, a molecule that encodes genetic information. DNA is a long polymer composed of four types of bases. The sequence of bases along a particular DNA molecule specify the genetic information, in a manner similar to a sequence of letters spelling out a word. Before a cell divides, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. Portions of a DNA molecule that specify a single functional unit are called genes; different genes have different sequences of bases. Within cells, the long strands of DNA form condensed structures called chromosomes. The specific location of a DNA sequence within a chromosome is known as a locus. If the DNA sequence at a locus varies between individuals, the different forms of this sequence are called alleles. DNA sequences can change through mutations, producing new alleles. If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism.

However, while this simple correspondence between an allele and a trait works in some cases, most traits are more complex and are controlled bymultiple interacting genes within and among organisms. Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlay some of the mechanics in developmental plasticity and canalization.

Recent findings have confirmed important examples of heritable changes that cannot be explained by direct agency of the DNA molecule. These phenomena are classed asepigenetic inheritance systems that are causally or independently evolving over genes. Research into modes and mechanisms of epigenetic inheritance is still in its scientific infancy, however, this area of research has attracted much recent activity as it broadens the scope of heritability and evolutionary biology in general. DNA methylation markingchromatin, self-sustaining metabolic loops, gene silencing by RNA interference, and the three dimensional conformation of proteins (such as prions) are areas where epigenetic inheritance systems have been discovered at the organismic level^. Heritability may also occur at even larger scales. For example, ecological inheritance through the process of niche construction is defined by the regular and repeated activities of organisms in their environment. This generates a legacy of effect that modifies and feeds back into the selection regime of subsequent generations. Descendants inherit genes plus environmental characteristics generated by the ecological actions of ancestors. Other examples of heritability in evolution that are not under the direct control of genes include the inheritance of cultural traits, group heritability, and symbiogenesis. These examples of heritability that operate above the gene are covered broadly under the title of multilevel or hierarchical selection, which has been a subject of intense debate in the history of evolutionary science.

Relation to theory of evolution

When Charles Darwin proposed his theory of evolution in 1859, one of its major problems was the lack of an underlying mechanism for heredity. Darwin believed in a mix of blending inheritance and the inheritance of acquired traits (pangenesis). Blending inheritance would lead to uniformity across populations in only a few generations and thus would remove variation from a population on which natural selection could act. This led to Darwin adopting some Lamarckian ideas in later editions of On the Origin of Species and his later biological works. Darwin's primary approach to heredity was to outline how it appeared to work (noticing that traits that were not expressed explicitly in the parent at the time of reproduction could be inherited, that certain traits could be sex-linked, etc.) rather than suggesting mechanisms.

Darwin's initial model of heredity was adopted by, and then heavily modified by, his cousin Francis Galton, who laid the framework for the biometric school of heredity. Galton rejected the aspects of Darwin's pangenesis model, which relied on acquired traits.

The inheritance of acquired traits was shown to have little basis in the 1880s when August Weismann cut the tails off many generations of mice and found that their offspring continued to develop tails.

Genetica

Genética

La genética es el campo de la biología que busca comprender la herencia biológica que se transmite de generación en generación. Genética proviene de la palabra γένος (gen) que en griego significa "descendencia".

El estudio de la genética permite comprender qué es lo que exactamente ocurre en el ciclo celular, (replicar nuestras células) y reproducción, (meiosis) de los seres vivos y cómo puede ser que, por ejemplo, entre seres humanos se transmitan características biológicas genotipo (contenido del genoma específico de un individuo en forma de ADN), características físicas fenotipo, de apariencia y hasta de personalidad.

El principal objeto de estudio de la genética son los genes, formados por segmentos de ADN (doble hebra) y ARN (hebra simple), tras la transcripicion de ARN mensajero, ARN ribosómico y ARN de transferencia, los cuales se sintetizan a partir de ADN. El ADN controla la estructura y el funcionamiento de cada célula, con la capacidad de crear copias exactas de sí mismo, tras un proceso llamado replicación,en el cual el ADN se replica.

En 1865 un monje estudioso de la herencia genética llamado Gregor Mendel observó que los organismos heredan caracteres de manera diferenciada. Estas unidades básicas de la herencia son actualmente denominadas genes.

En 1941 Edward Lawrie Tatum y George Wells Beadle demuestran que los genes [ARN-mensajero] codifican proteínas; luego en 1953 James D. Watson y Francis Crick determinan que la estructura del ADN es una doble hélice en direcciones antiparalelas, polimerizadas en dirección 5' a 3', para el año 1977 Fred Sanger, Walter Gilbert, y Allan Maxam secuencian ADN completo del genoma del bacteriófago y en 1990 se funda el Proyecto Genoma Humano.

La ciencia de la genética

Aunque la genética juega un papel muy significativo en la apariencia y el comportamiento de los organismos, es la combinación de la genética [replicación, transcripción, procesamiento (maduración del ARN] con las experiencias del organismo la que determina el resultado final.

Los genes corresponden a regiones del ADN o ARN, dos moléculas compuestas de una cadena de cuatro tipos diferentes de bases nitrogenadas (adenina, timina, citosina yguanina en ADN), en las cuales tras la transcripcion (síntesis de ARN) se cambia la timina por uracilo —la secuencia de estos nucleótidos es la información genética que heredan los organismos. El ADN existe naturalmente en forma bicatenaria, es decir, en dos cadenas en que los nucleótidos de una cadena complementan los de la otra.

La secuencia de nucleótidos de un gen es traducida por las células para producir una cadena de aminoácidos, creando proteínas —el orden de los aminoácidos en una proteína corresponde con el orden de los nucleótidos del gen. Esto recibe el nombre de código genético. Los aminoácidos de una proteína determinan cómo se pliega en una forma tridimensional y responsable del funcionamiento de la proteína. Las proteínas ejecutan casi todas las funciones que las células necesitan para vivir.

El genoma es la totalidad de la información genética que posee un organismo en particular. Por lo general, al hablar de genoma en los seres eucarióticos nos referimos sólo al ADN contenido en el núcleo, organizado en cromosomas. Pero no debemos olvidar que también la mitocondria contiene genes llamado genoma mitocondrial.

Subdivisiones de la genética

La genética se subdivide en varias ramas, como:

• Clásica o mendeliana: Se preocupa del estudio de los cromosomas y los genes y de cómo se heredan de generación en generación.
• Cuantitativa, que analiza el impacto de múltiples genes sobre el fenotipo, muy especialmente cuando estos tienen efectos de pequeña escala.
• Molecular: Estudia el ADN, su composición y la manera en que se duplica. Asi mismo, estudia la función de los genes desde el punto de vista molecular.
• Evolutiva y de poblaciones: Se preocupa del comportamiento de los genes en una población y de cómo esto determina la evolución de los organismos. En la genetica se pueden encontrar muchos rasgos familiares en comun de la familia como el color de ojos, el color de piel y el color del cabello.

Importancia de la genética

El conocimiento genético ha permitido la mejora extensa en productividad de plantas usadas para el alimento como por ejemplo el arroz, trigo, y el maíz. El conocimiento genético también ha sido un componente dominante de la revolución en salud y asistencia médica en este siglo.

Su importancia en la rama de la Bioingeniería ha sido alterar el material genético de un organismo.

Permite alterar diversos segmentos del ADN, adquiriendo genes nuevos y nuevos rasgos genéticos, así como evitar malformaciones en el ADN.

En el área de la salud ha permitido el tratamiento y prevenir la repetición del Síndrome de Down. La bioingeniería ofrece la esperanza de crear antibióticos más eficaces, además de el descubrimiento de una hormona del crecimiento para combatir el enanismo.

Sin duda la genética juega un papel muy importante en la evolución de la especie, y la erradicación de enfermedades genéticas.

Genetics

Genetics (from Ancient Greek γενετικός genetikos, "genitive" and that from γένεσις genesis, "origin"),
a discipline of biology, is the science of genes,heredity, and variation in living organisms.
Genetics deals with the molecular structure and function of genes, gene behavior in context of a cell or organism (e.g. dominance and epigenetics), patterns of inheritance from parent to offspring, and gene distribution, variation and change in populations,such as through Genome-Wide Association Studies. Given that genes are universal to living organisms, genetics can be applied to the study of all living systems, from viruses and bacteria, throughplants and domestic animals, to humans (as in medical genetics).

The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding. However, the modern science of genetics, which seeks to understand the process of inheritance, only began with the work of Gregor Mendel in the mid-19th century.^[6] Although he did not know the physical basis for heredity, Mendel observed that organisms inherit traits via discrete units of inheritance, which are now called genes.

Genes correspond to regions within DNA, a molecule composed of a chain of four different types of nucleotides—the sequence of these nucleotides is the genetic information organisms inherit. DNA naturally occurs in a double stranded form, with nucleotides on each strand complementary to each other. Each strand can act as a template for creating a new partner strand. This is the physical method for making copies of genes that can be inherited.

The sequence of nucleotides in a gene is translated by cells to produce a chain of amino acids, creating proteins—the order of amino acids in a protein corresponds to the order of nucleotides in the gene. This relationship between nucleotide sequence and amino acid sequence is known as the genetic code. The amino acids in a protein determine how it folds into a three-dimensional shape; this structure is, in turn, responsible for the protein's function. Proteins carry out almost all the functions needed for cells to live. A change to the DNA in a gene can change a protein's amino acids, changing its shape and function: this can have a dramatic effect in the cell and on the organism as a whole.

Although genetics plays a large role in the appearance and behavior of organisms, it is the combination of genetics with what an organism experiences that determines the ultimate outcome. For example, while genes play a role in determining an organism's size, the nutrition and health it experiences after inception also have a large effect.

History

Although the science of genetics began with the applied and theoretical work of Gregor Mendel in the mid-19th century, other theories of inheritance preceded Mendel. A popular theory during Mendel's time was the concept of blending inheritance: the idea that individuals inherit a smooth blend of traits from their parents. Mendel's work provided examples where traits were definitely not blended after hybridization, showing that traits are produced by combinations of distinct genes rather than a continuous blend. Blending of traits in the progeny is now explained by the action of multiple genes withquantitative effects. Another theory that had some support at that time was the inheritance of acquired characteristics: the belief that individuals inherit traits strengthened by their parents. This theory (commonly associated with Jean-Baptiste Lamarck) is now known to be wrong—the experiences of individuals do not affect the genes they pass to their children. Other theories included the pangenesis of Charles Darwin (which had both acquired and inherited aspects) and Francis Galton's reformulation of pangenesis as both particulate and inherited.

Mendelian and classical genetics

Modern genetics started with Gregor Johann Mendel, a German-Czech Augustinian monk and scientist who studied the nature of inheritance in plants. In his paper "Versuche über Pflanzenhybriden" ("Experiments on Plant Hybridization"), presented in 1865 to the Naturforschender Verein (Society for Research in Nature) in Brünn, Mendel traced the inheritance patterns of certain traits in pea plants and described them mathematically.^[9] Although this pattern of inheritance could only be observed for a few traits, Mendel's work suggested that heredity was particulate, not acquired, and that the inheritance patterns of many traits could be explained through simple rules and ratios.

The importance of Mendel's work did not gain wide understanding until the 1890s, after his death, when other scientists working on similar problems re-discovered his research. William Bateson, a proponent of Mendel's work, coined the word genetics in 1905. (The adjective genetic, derived from the Greek word genesis—γένεσις, "origin", predates the noun and was first used in a biological sense in 1860.) Bateson popularized the usage of the word genetics to describe the study of inheritance in his inaugural address to the Third International Conference on Plant Hybridization in London, England, in 1906.

After the rediscovery of Mendel's work, scientists tried to determine which molecules in the cell were responsible for inheritance. In 1911, Thomas Hunt Morgan argued that genes are on chromosomes, based on observations of a sex-linked white eye mutation in fruit flies.^[14] In 1913, his student Alfred Sturtevant used the phenomenon of genetic linkage to show that genes are arranged linearly on the chromosome.

Nature versus nurture

Although genes contain all the information an organism uses to function, the environment plays an important role in determining the ultimate phenotype—a phenomenon often referred to as "nature vs. nurture". The phenotype of an organism depends on the interaction of genetics with the environment. One example of this is the case of temperature-sensitive mutations. Often, a single amino acid change within the sequence of a protein does not change its behavior and interactions with other molecules, but it does destabilize the structure. In a high temperatureenvironment, where molecules are moving more quickly and hitting each other, this results in the protein losing its structure and failing to function. In a low temperature environment, however, the protein's structure is stable and it functions normally. This type of mutation is visible in the coat coloration of Siamese cats, where a mutation in an enzyme responsible for pigment production causes it to destabilize and lose function at high temperatures.The protein remains functional in areas of skin that are colder—legs, ears, tail, and face—and so the cat has dark fur at its extremities.

Environment also plays a dramatic role in effects of the human genetic disease phenylketonuria.The mutation that causes phenylketonuria disrupts the ability of the body to break down the amino acid phenylalanine, causing a toxic build-up of an intermediate molecule that, in turn, causes severe symptoms of progressive mental retardation and seizures. If someone with the phenylketonuria mutation follows a strict diet that avoids this amino acid, however, they remain normal and healthy.

A popular method to determine how much role nature and nurture play is to study identical and fraternal twins or siblings of multiple birth.Because identical siblings come from the same zygote they are genetically the same. Fraternal siblings however are as different genetically from one another as normal siblings. By comparing how often the twin of a set has the same disorder between fraternal and identical twins, scientists can see whether there is more of a nature or nurture effect. One famous example of a multiple birth study includes the Genain quadruplets, who were identical quadruplets all diagnosed with schizophrenia.

Medicine

Medical genetics seeks to understand how genetic variation relates to human health and disease. When searching for an unknown gene that may be involved in a disease, researchers commonly use genetic linkage and genetic pedigree charts to find the location on the genome associated with the disease. At the population level, researchers take advantage of Mendelian randomization to look for locations in the genome that are associated with diseases, a method especially useful for multigenic traits not clearly defined by a single gene. Once a candidate gene is found, further research is often done on the corresponding gene (called an orthologous gene) in model organisms. In addition to studying genetic diseases, the increased availability of genotyping methods has led to the field of pharmacogenetics—studying how genotype can affect drug responses.

Individuals differ in their inherited tendency to develop cancer,and cancer is a genetic disease. The process of cancer development in the body is a combination of events.Mutations occasionally occur within cells in the body as they divide. Although these mutations will not be inherited by any offspring, they can affect the behavior of cells, sometimes causing them to grow and divide more frequently. There are biological mechanisms that attempt to stop this process; signals are given to inappropriately dividing cells that should trigger cell death, but sometimes additional mutations occur that cause cells to ignore these messages. An internal process of natural selection occurs within the body and eventually mutations accumulate within cells to promote their own growth, creating a cancerous tumor that grows and invades various tissues of the body.

Normally, a cell divides only in response to signals: "growth factors", it stops growing when making contact with surrounding cells (contact inhibition), and in response to growth inhibitory signals, it divides a limited number of times and dies (apoptosis), it stays inside the epithelium and is not able to migrate to invade other organs. To become a cancer cell, a cell has to accumulate mutations in a number of genes (3-7) that allow it to bypass all these regulations: it no longer needs growth factors to divide, it continues growing when making contact to neighbor cells, and ignores inhibitory signals, it will keep growing indefinitely and is immortal, it will escape from the epithelium and ultimately may be able to escape from the primary tumor, cross the endothelium of a blood vessel, be transported by the bloodstream and will colonize a new organ, forming deadly metastasis. Although there are some genetic predispositions in a small fraction of cancers, the major fraction is due to a set of new genetic mutations that originally appear and accumulate in one or a small number of cells that will divide to form the tumor and are not transmitted to the progeny (somatic mutations). The most frequent mutations are a loss of function of p53 protein, a tumor suppressor, or in the p53 pathway, and gain of function mutations in the ras proteins, or in other oncogenes.

For human genetic diseases see Genetic Disorders.

Bibliografia
http://www.youtube.com/watch?v=ifsqgucj_J4
http://es.wikipedia.org/wiki/Clonaci%C3%B3n_(biolog%C3%ADa)
http://es.wikipedia.org/wiki/Gen%C3%A9tica
http://es.wikipedia.org/wiki/Herencia_gen%C3%A9tica