Genetics is the study of genes, genetic variations, and heredity in living organisms. It is generally regarded as a field of biology, but it is often cut with many other life sciences and is strongly associated with the study of information systems.
The inventor of genetics is Gregor Mendel, a nineteenth-century scientist and Augustinian monk. Mendel studied "inherited traits", patterns in ways derived from parents to offspring. He observes that organisms (pea plants) inherit traits by means of discrete "inherited units". This term, still used today, is a rather ambiguous definition of what is called a gene.
Molecular inheritance and molecular inheritance mechanisms of genes are still the main principles of genetics in the 21st century, but modern genetics has evolved beyond inheritance to study the function and behavior of genes. Gene structures and functions, variations, and distributions are studied in the context of cells, organisms (eg dominance), and in the context of populations. Genetics has spawned a number of subfields, including epigenetic and population genetics. The organisms studied in the wide span of life domain (archaea, bacteria, and eukarya).
The genetic process works in combination with the environment and the organism's experience to influence development and behavior, often referred to as nature versus parenting. The intracellular or extracellular environment of a cell or organism may alter or deactivate gene transcription. The classic examples are two genetically identical corn kernels, one placed in a temperate climate and one in a dry climate. While the average height of two corn stalks may be genetically determined equally, one in dry climates grows only half the height in the temperate climate due to lack of water and nutrients in the environment.
Video Genetics
Etimologi
The word genetics comes from the ancient Greek ????????? geneticos meaning "genitive"/"generative", which in turn comes from < span lang = "grc" title = "Ancient Greek subtitle"> ??????? genesis which means "origin".
Maps Genetics
History
The observation that living things inherited the properties of their parents has been used since prehistoric times to improve plant and animal crops through selective breeding. The science of modern genetics, which seeks to understand this process, begins with the work of Augustinian monk Gregor Mendel in the mid-19th century.
Before Mendel, Imre Festetics, a Hungarian noble, living in K? Szeg before Mendel, was the first to use the word "genetics." He describes some genetic inheritance rules in his Natural Genetic Law (Die genetische GesÃÆ'¤tze der Natur, 1819). The second law is the same as what Mendel publishes. In its third law, he developed the basic principle of mutation (he could be regarded as the pioneer of Hugo de Vries).
Another theory of inheritance precedes Mendel's work. A popular theory during the 19th century, and implied by Charles Darwin in 1859 On the Origin of Species , is the mixing of inheritance: the idea that individuals inherit the subtle mixed properties of their parents. Mendel's work provides examples where definite characteristics are not mixed after hybridization, suggesting that they are produced by different combinations of genes rather than ongoing mixes. Integrating traits in heredity is now explained by the action of several genes with quantitative effects. Another theory that had some support at the time was a characteristic inheritance gained: the belief that individuals inherit the properties reinforced by their parents. This theory (commonly associated with Jean-Baptiste Lamarck) is now known to be false - individual experiences do not affect the genes they give to their children, although evidence in the field of epigenetics has rekindled some aspects of Lamarck's theory. Other theories include Charles Darwin pangenesis (which has acquired and inherited aspects) and Francis Galton's reformulation of pangenesis as particulate and inherited.
Mendel's Genetics and classics
Modern genetics begins with Mendel's study of the nature of inheritance in plants. In his paper " Versuche ÃÆ'¼ber Pflanzenhybriden " ("Experiments on Plant Hybridization"), presented in 1865 to the Naturforschender Verein (Society for Research in Nature) at BrÃÆ'¼nn, Mendel traced the pattern inheritance of certain properties in pea plants and described mathematically. Although this pattern of inheritance can only be observed for some traits, Mendel's work shows that heredity is particulate, not obtained, and that the pattern of inheritance of many traits can be explained by simple rules and ratios.
The importance of Mendel's work did not gain widespread understanding until 1900, after his death, when Hugo de Vries and other scientists rediscovered his research. William Bateson, a supporter of Mendel's work, invented the word genetics in 1905 (the genetic adjective , derived from the Greek word genesis -? ???, "Origin", preceded the noun and was first used in a biological sense in 1860). Bateson both acted as mentors and assisted significantly by the work of female scientists from Newnham College in Cambridge, in particular the work of Becky Saunders, Nora Darwin Barlow, and Muriel Wheldale Onslow. Bateson popularized the use of the word genetics to describe inheritance studies in his inaugural address to the Third International Conference on Plant Hybridization in London in 1906.
After the rediscovery of Mendel's work, scientists are trying to determine which molecules in the cell are responsible for inheritance. In 1911, Thomas Hunt Morgan argued that genes were on chromosomes, based on observations of white-linked eye mutations in fruit flies. In 1913, his disciple Alfred Sturtevant used the phenomenon of genetic linkage to show that genes are arranged linearly on chromosomes.
Genetika molekuler
Although genes are known to exist on chromosomes, chromosomes are composed of proteins and DNA, and scientists do not know which of the two are responsible for inheritance. In 1928, Frederick Griffith discovered the phenomenon of transformation (see Griffith's experiment): dead bacteria can transfer genetic material to "transform" other living bacteria. Sixteen years later, in 1944, the Avery-MacLeod-McCarty experiment identified DNA as the molecule responsible for transformation. The core role as a repository of genetic information in eukaryotes was established by HÃÆ'¤mmerling in 1943 in his work on single celled algae Acetabularia . The Hershey-Chase experiment in 1952 confirmed that DNA (not protein) is the genetic material of a virus that infects bacteria, providing further evidence that DNA is a molecule responsible for inheritance.
James Watson and Francis Crick determined the structure of DNA in 1953, using the work of Xal Rosalind Franklin and Maurice Wilkins's X-ray crystallography which indicates DNA has a helical structure (ie, shaped like a bottle opener). Their double-helix model has two DNA strands with nucleotides pointing inward, each matching a complementary nucleotide on another strand to form what looks like a staircase on a crooked ladder. This structure shows that genetic information exists in a nucleotide sequence on each strand of DNA. The structure also suggests a simple method for replication: if the strands are separated, new partner strands can be reconstructed for each based on the order of the old strand. This property is what gives DNA a semi-conservative nature in which a new strand of DNA comes from the original parent strand.
Although the structure of DNA shows how inheritance works, it remains unknown how DNA affects cell behavior. In the years that followed, scientists tried to understand how DNA controls the protein production process. It was found that cells use DNA as a template to create matching messenger RNAs, molecules with nucleotides that are very similar to DNA. The nucleotide sequence of the messenger RNA is used to create a sequence of amino acids in proteins; this translation between the nucleotide sequence and the amino acid sequence is known as the genetic code.
With a new understanding of inheritance, explosive research emerged. A famous theory emerged from Tomoko Ohta in 1973 with his amendment to the neutral theory of molecular evolution through the publication of an almost neutral molecular evolutionary theory. In this theory, Ohta emphasizes the importance of natural selection and the environment to the extent to which genetic evolution takes place. One of the most important developments was the chain-ending DNA sequence in 1977 by Frederick Sanger. This technology allows scientists to read the nucleotide sequence of a DNA molecule. In 1983, Kary Banks Mullis developed a polymerase chain reaction, providing a quick way to isolate and amplify specific parts of DNA from the mixture. The Human Genome Project, Department of Energy, NIH, and parallel personal efforts by Celera Genomics led to the human genome sequence in 2003.
Inheritance features
Discrete and Mendelian legacy
At the most fundamental level, inheritance in organisms occurs by giving discrete inherited units, called genes, from parents to offspring. This property was first observed by Gregor Mendel, who studied the inherited segregation of trait in bean plants. In his experiments studying properties for the color of flowers, Mendel observes that the flowers of any pea plants are either purple or white - but never intermediate between the two colors. Different and separate versions of the same genes are called alleles.
In the case of peas, which are diploid species, each plant has two copies of each gene, one copy inherited from each parent. Many species, including humans, have this inheritance pattern. The diploid organisms with two copies of the same allele of the given gene are called homozygous at the gene locus, while organisms with two different alleles of the given gene are called heterozygotes.
A set of alleles for a particular organism is called its genotype, while the observable trait of an organism is called its phenotype. When organisms are heterozygous in genes, often one allele is called dominant as its quality dominates the phenotype of the organism, while the other allele is called recessive as its quality recedes and is not observed. Some alleles do not have full dominance and instead have incomplete dominance by expressing intermediate phenotypes, or codominance by expressing both alleles at once.
When a pair of organisms reproduce sexually, their offspring randomly inherit one of two alleles from each parent. This observation of the discrete inheritance and segregation of alleles is collectively known as Mendel's first law or the Law of Segregation.
Notations and diagrams
Geneticists use diagrams and symbols to describe inheritance. A gene is represented by one or more letters. Often "" symbols are used to mark regular, non-mutant alleles for genes.
In conception and breeding experiments (and especially when discussing Mendel's laws) parents are referred to as "P" generation and descendants as "F1" generation (first generation). When the F1 pair mates with each other, the offspring is called "F2" generation (second generation). One of the common diagrams used to predict the crosses is Punnett square.
When studying human genetic diseases, geneticists often use genealogical charts to represent the inheritance of traits. These charts map the inheritance of a trait in the family tree.
Double gene interactions
Organisms have thousands of genes, and in sexually reproducing organisms, these genes generally pair up independently of each other. This means that inheritance of alleles for yellow or green peanut color is not associated with inheritance of alleles for white or purple flowers. This phenomenon, known as Mendel's "second law" or "various independent law", means that different gene alleles are shuffling between parents to form offspring with many different combinations. (Some genes do not pair independently, indicate genetic linkages, topics discussed later in this article.)
Often different genes can interact in ways that affect the same trait. In Blue-eyed Mary (Omphalodes verna ), for example, there is a gene with an allele that determines the color of the flower: blue or magenta. Other genes, however, control whether the flower has any color at all or white. When a plant has two copies of this white allele, the flowers are white - regardless of whether the first gene has a blue allele or magenta. The interaction between these genes is called epistasis, with the second gene being epistatic to the first.
Many features are not separate features (such as purple or white flowers) but are a continuous feature (eg, the height and color of human skin). These intricate features are the product of many genes. The influence of these genes is mediated, to varying degrees, by the environment experienced by an organism. The extent to which a gene of an organism contributes to the complex nature is called heritability. Measuring the heritability of a relative trait - in a more varied environment, the environment has a greater influence on the total variation of the trait. For example, human height is a trait with complex causes. It has 89% heritability in the United States. But in Nigeria, where people experience more diverse access to good nutrition and health care, it has a high rate of only 62%.
The molecular basis for inheritance
DNA and chromosomes
The molecular basis for the gene is deoxyribonucleic acid (DNA). DNA consists of nucleotide chains, consisting of four types: adenine (A), cytosine (C), guanine (G), and thymine (T). Genetic information exists in this nucleotide sequence, and genes exist as sequences of strings along the DNA chain. Viruses are the only exceptions to this rule - sometimes the virus uses a very similar RNA molecule rather than DNA as their genetic material. The virus can not reproduce without host and is unaffected by many genetic processes, so it is unlikely to be considered a living organism.
DNA usually exists as a double-stranded molecule, rolled into a double helix shape. Each nucleotide in DNA is paired with its partner's nucleotide on the opposite strand: The pair with T, and C are paired with G. Thus, in the form of two strands, each strand effectively contains all the necessary information, exaggerated with its partner strand. This DNA structure is the physical basis for inheritance: DNA replication duplicates the genetic information by separating the threads and using each strand as a template for synthesizing a new partner strand.
Genes are arranged linearly along the long chain of DNA base pair pairs. In bacteria, each cell usually contains a single circular genophore, while eukaryotic organisms (such as plants and animals) have their DNA arranged in several linear chromosomes. These DNA strands are often very long; the largest human chromosome, for example, about 247 million long base pairs. DNA from chromosomes is associated with structural proteins that regulate, compact, and control access to DNA, forming a substance called chromatin; in eukaryotes, chromatin is usually composed of nucleosomes, segments of DNA lesions around the histone protein core. A complete set of hereditary materials in an organism (usually a combination of DNA sequences of all chromosomes) is called the genome.
While haploid organisms have only one copy of each chromosome, most animals and many plants are diploid, containing two of each chromosome and two copies of each gene. The two alleles for the gene lie in the identical locus of two homologous chromosomes, each of which is the allele inherited from a different parent.
Many species have sex chromosomes that determine the sex of every organism. In humans and many other animals, the Y chromosome contains genes that trigger the development of male-specific characteristics. In evolution, this chromosome has lost most of its contents as well as most of its genes, while the X chromosome is similar to other chromosomes and contains many genes. X and Y chromosomes form very heterogeneous pairs.
Reproduction
When cells divide, their full genome is copied and each child cell inherits one copy. This process, called mitosis, is the simplest form of reproduction and is the basis for asexual reproduction. Asexual reproduction can also occur in multicell organisms, producing offspring that inherit their genomes from single parents. Descendants that are genetically identical to their parents are called clones.
Eukaryotic organisms often use sexual reproduction to produce offspring that contain a mixture of genetic material inherited from two different parents. The process of sexual reproduction alternates between forms containing single (haploid) and double copies (diploid) copies. Haploid cells converge and combine genetic material to create diploid cells with paired chromosomes. Diploid organisms form haploids by dividing, without replicating their DNA, to create a daughter cell that randomly inherits one of each pair of chromosomes. Most animals and many plants are diploid for most of their lifetime, with haploid forms reduced to single cell gametes such as sperm or eggs.
Although they do not use the haploid/diploid sexual reproductive method, bacteria have many methods for obtaining new genetic information. Some bacteria may experience conjugation, transferring a small circular piece of DNA to other bacteria. Bacteria can also pick up raw DNA fragments found in the environment and integrate them into their genome, a phenomenon known as transformation. These processes produce horizontal gene transfer, transmitting fragments of genetic information between organisms that will be unrelated.
Genetic recombination and linkage
The diploid nature of chromosomes allows genes on different chromosomes to pair independently or separated from their homologous pairs during sexual reproduction in which haploid gametes are formed. In this way new gene combinations can occur in the offspring of the mating pair. The genes on the same chromosome will theoretically never rejoin. However, they do so, through a crossover chromosome cellular process. During crossovers, chromosomes exchange stretches of DNA, effectively shuffling gene alleles between chromosomes. This chromosome crossover process generally occurs during meiosis, a series of cell divisions that create haploid cells.
The first cyberspace demonstration was deviated by Harriet Creighton and Barbara McClintock in 1931. Their research and experiments on corn provide cytological evidence for the genetic theory that links genes on a paired chromosome in fact exchange places from one homologue to another.
The probability of a chromosome crossover occurring between two points given on a chromosome is related to the distance between points. For long distances, the probability of crossover is high enough that gene inheritance is effectively uncorrelated. For closer genes, however, the lower probability of crossover means that genes exhibit a genetic link; alleles for two genes tend to be inherited together. The number of links between gene sequences can be combined to form a linear relationship map that roughly describes the arrangement of genes along the chromosomes.
Gene expression
Genetic code
Genes generally express their functional effects through the production of proteins, which are complex molecules responsible for most of the functions in the cell. Proteins comprise one or more polypeptide chains, each composed of a series of amino acids, and a gene DNA sequence (via intermediate RNA) used to produce a specific amino acid sequence. This process begins with the production of RNA molecules in sequences that correspond to the sequence of gene DNA, a process called transcription.
This messenger RNA molecule is then used to produce an appropriate amino acid sequence through a process called translation. Each group of three nucleotides in a sequence, called a codon, corresponds to one of twenty possible amino acids in the protein or an instruction to terminate the amino acid sequence; This correspondence is called the genetic code. The flow of information is not unidirectional: information is transferred from the nucleotide sequence to the amino acid sequence of the protein, but never moves from the protein back to the DNA sequence - a phenomenon Francis Crick is called the central dogma of molecular biology.
The specific sequence of amino acids produces a unique three-dimensional structure for the protein, and the three-dimensional structure of the protein is related to its function. Some are simple structural molecules, such as fibers formed by collagen proteins. Proteins can bind to proteins and other simple molecules, sometimes acting as enzymes by facilitating chemical reactions in bound molecules (without changing the structure of the protein itself). Protein structure is dynamic; the hemoglobin protein bends into slightly different forms as it facilitates the capture, transport, and release of oxygen molecules in mammalian blood.
A single nucleotide difference in DNA can cause changes in the amino acid sequence of a protein. Because protein structure is the result of their amino acid sequence, some changes can dramatically alter the properties of proteins by destabilizing structures or altering the surface of proteins in a way that alters their interactions with proteins and other molecules. For example, sickle cell anemia is a human genetic disease resulting from a single base difference in the coding region for the hemoglobin-globin section, causing a change in a single amino acid that alters the physical properties of hemoglobin. The crescent sickle cell version attaches itself, accumulating to form fibers that distort the shape of red blood cells that carry proteins. These sickle-shaped cells no longer flow smoothly through the blood vessels, have a tendency to clog or degrade, causing medical problems associated with this disease.
Some DNA sequences are transcribed into RNA but not translated into protein products - RNA molecules thus called non-coding RNA. In some cases, these products fold into structures involved in critical cell functions (eg ribosomal RNA and RNA transfer). RNA can also have regulatory effects through hybridization interactions with other RNA molecules (eg microRNA).
Nature and maintain
Although genes contain all the information that organisms use to function, the environment plays an important role in determining the final phenotype that organisms display. The phrase "nature and nurture" refers to this complementary relationship. The phenotype of an organism depends on the interaction of genes and the environment. An interesting example is the staining of the Siamese cat mantle. In this case, the cat's body temperature plays an environmental role. Code the cat genes for dark hair, so the hair-producing cells in cats make cellular proteins produce dark hair. But these black hair-producing proteins are sensitive to temperature (ie having a mutation that causes temperature sensitivity) and denaturation in high temperature environments, failing to produce dark hair pigments in areas where cats have higher body temperatures. In a low-temperature environment, the protein structure is stable and produces normal dark-pigmented hair. Protein stays functioning in areas of colder skin - such as the feet, ears, tail and face - so the cat has black hair at the ends.
The environment plays a major role in the phenylketonuria effect of human genetic disease. Mutations that cause phenylketonuria interfere with the body's ability to break down the amino acid phenylalanine, leading to the formation of toxic intermediate molecules, which in turn, leads to severe symptoms of progressive intellectual disability and seizures. However, if someone with phenylketonuria mutations follows a strict diet that avoids these amino acids, they remain normal and healthy.
Common methods for determining how genes and environments ("nature and nurture") contribute to phenotypes involving studying identical and fraternal twins, or other twin siblings of twinning. Since identical siblings come from the same zygote, they are genetically alike. Birth twins are just as genetically different from each other as normal siblings. By comparing how often certain disorders occur in identical twin pairs with how often it occurs in a pair of fraternal twins, scientists can determine whether the disorder is caused by genetic environmental factors or after birth - whether it has "properties" or "maintenance". One of the notable examples involves the study of Genain quadruplets, which are identical twin twins that are all diagnosed with schizophrenia, but such tests can not separate genetic factors from environmental factors that affect fetal development.
Gene rules
The genome of a particular organism contains thousands of genes, but not all of these genes must be active at any given moment. A gene is expressed while being transcribed to mRNA and there are many cellular methods controlling gene expression so that proteins are only produced when needed by the cell. Transcription factors are regulatory proteins that bind DNA, either promoting or inhibiting gene transcription. In the bacterial genome Escherichia coli , for example, there is a series of genes necessary for the synthesis of tryptophan amino acids. However, when tryptophan is readily available to cells, these genes for tryptophan synthesis are no longer necessary. The presence of tryptophan directly affects the activity of the gene - the tryptophan molecule binds to a tryptophan repressor (transcription factor), alters the structure of the repressor in such a way that the repressor binds to the gene. Tryptophan repressors block transcription and gene expression, thus creating negative feedback regulation of the tryptophan synthesis process.
The differences in gene expression are very evident in multicellular organisms, in which all cells contain the same genome but have very different structures and behaviors due to the expression of different sets of genes. All cells in multicellular organisms come from a single cell, which differentiates them into variant cell types in response to external and intercellular signals and gradually forms different gene expression patterns to create different behaviors. Since no single gene is responsible for the development of structures in multicellular organisms, these patterns arise from complex interactions between many cells.
In eukaryotes, there is a structural feature of chromatin that affects the transcription of genes, often in the form of DNA and chromatin modifications that are inherently inherited by the child's cells. These features are called "epigenetic" because they exist "above" from the DNA sequence and retain inheritance from one generation of cells to the next. Because of the epigenetic features, different types of cells that grow in the same medium can retain very different properties. Although epigenetic features are generally dynamic during development, some, such as the phenomena of paramutation, have multigenerational inheritance and exist as rare exceptions to the general rule of DNA as the basis of inheritance.
Genetic change
Mutations
During the DNA replication process, there is sometimes an error in the polymerization of the second strand. These errors, called mutations, can affect the phenotype of an organism, especially if they occur in the sequence of protein coding of a gene. The error rate is usually very low - 1 error in every 10-100 million bases - due to the ability to "correct" the DNA polymerase. The process that increases the rate of DNA change is called mutagenic: mutagenic chemicals promote errors in DNA replication, often by disrupting the structure of the base pair, while UV radiation induces mutations by causing damage to the DNA structure. Chemical damage to DNA occurs naturally as well and cells use DNA repair mechanisms to correct mismatches and damage. However, the fixes do not always return the original order.
In organisms that use crossover chromosomes to exchange DNA and recombine genes, errors in alignment during meiosis can also cause mutations. Errors in crossovers are highly likely when the same sequence causes partner chromosomes to adopt faulty alignment; this makes some areas of the genome more vulnerable to mutate in this way. This error creates major structural changes in the DNA sequence - duplication, inversion, deletion of entire territory - or accidental exchange of all parts of the circuit between different chromosomes (chromosomal translocation).
Natural selection and evolution
Mutations alter the genotype of the organism and sometimes this causes a different phenotype to emerge. Most mutations have little effect on the phenotype, health, or fitness of organism reproduction. Mutations that do have an effect are usually detrimental, but sometimes some can be beneficial. Rapid studies of Drosophila melanogaster show that if mutations alter the protein produced by genes, about 70 percent of these mutations would be harmful with the rest either neutral or less useful.
The genetic population studies the distribution of genetic differences in populations and how these distributions change over time. The frequency change of alleles in a population is mainly influenced by natural selection, in which the given allele provides selective or reproductive advantages to the organism, as well as other factors such as mutations, genetic drift, genetic assault, artificial selection and migration..
For generations, the genomes of organisms can change significantly, resulting in evolution. In a process called adaptation, selection for a favorable mutation can cause a species to evolve into a form that is better able to survive in their environment. New species are formed through the process of speciation, often caused by geographic separation that prevents populations from exchanging genes with one another.
By comparing homology between the genomes of different species, it is possible to calculate the evolutionary distance between them and when they may have diverged. Genetic comparisons are generally regarded as a more accurate method of characterizing the linkages between species than the comparison of phenotypic characteristics. The distance between species evolution can be used to form an evolutionary tree; these trees represent common ancestry and species differences over time, although they do not show the transfer of genetic material between unrelated species (known as horizontal gene transfer and most common in bacteria).
Model organism
Although geneticists initially studied inheritance in various organisms, researchers began to specialize in studying the genetics of a subset of certain organisms. The fact that significant research already exists for certain organisms will encourage new researchers to select it for further study, and finally some organism models form the basis for most genetic studies. General research topics in the genetics of organism models include studies of gene regulation and gene involvement in development and cancer.
Organisms are selected, in part, for convenience - short-time generation and easy gene manipulation of several popular genetic research tools. Models of widely used organisms include intestinal bacteria Escherichia coli, Arabidopsis thaliana plant, baking yeast (Saccharomyces cerevisiae), nematodes Caenorhabditis elegans , common fruit flies ( Drosophila melanogaster ), and common house mice ( Medicine
Medical genetics seeks to understand how genetic variations are related to human health and disease. When looking for unknown genes that may be involved in a disease, researchers usually use genetic links and genetic genealogical charts to locate the genomes associated with the disease. At the population level, researchers took advantage of Mendel's scrambling to locate in the disease-related genome, a very useful method for multigenic properties that is not clearly defined by a single gene. Once the candidate genes are discovered, more research is often done on the appropriate (or homologous) genes of the model organism. In addition to studying genetic diseases, increased availability of genotype methods has led to the field of pharmacogenetics: the study of how genotypes can affect drug responses.
Individuals differ in their inherited tendencies to develop cancer, and cancer is a genetic disease. The process of cancer development in the body is a combination of events. Mutations sometimes occur inside cells in the body as they divide. Although these mutations will not be inherited by any offspring, they can affect cell behavior, sometimes causing them to grow and divide more often. There are biological mechanisms that try to stop this process; signals are given to improper dividing cells that should trigger cell death, but sometimes additional mutations occur that cause cells to ignore these messages. The internal process of natural selection takes place inside the body and ultimately mutations accumulate inside cells to promote their own growth, creating cancerous tumors that grow and attack various body tissues.
Typically, cells divide only in response to a signal called growth factor and stop growing after contact with surrounding cells and in response to growth inhibition signals. Usually then divide it in limited quantities and die, staying in the epithelium where it can not migrate to other organs. To become a cancer cell, the cell must accumulate mutations in a number of genes (three to seven) that allow it to pass through this rule: it no longer requires growth factors to divide, continues to grow when making contact with neighboring cells, ignoring inhibition. signals, continues to grow indefinitely and endlessly, escape from the epithelium and may eventually escape from the primary tumor, cross the vascular endothelium, transported by the bloodstream and colonize the new organ, forming a deadly metastasis. Although there is some genetic predisposition in small fragments of cancer, the main fraction is due to a set of new genetic mutations that originally appeared and accumulated in one or a small number of cells that will divide to form a tumor and not transmitted to the progeny (somatic mutation). The most common mutations are loss of p53 protein function, tumor suppressor, or p53 pathway, and acquire function mutations in Ras proteins, or on other oncogenes.
Research method
DNA can be manipulated in the laboratory. Restriction enzymes are commonly used enzymes that cut DNA in a specific sequence, producing predictable DNA fragments. DNA fragments can be visualized through the use of gel electrophoresis, which separates fragments according to their length.
The use of ligation enzymes allows the DNA fragments to be connected. By binding ("binding") the DNA fragments together from different sources, researchers can make recombinant DNA, a DNA often associated with genetically modified organisms. Recombinant DNA is usually used in the plasmid context: a short circular DNA molecule with several genes on it. In a process known as molecular cloning, researchers can amplify DNA fragments by inserting plasmids into bacteria and then culturing them in agar plates (to isolate clonal cell clones - "cloning" can also refer to various ways of creating cloning ("clonal") organisms).
DNA can also be amplified using a procedure called polymerase chain reaction (PCR). Using a short series of specific DNA, PCR can isolate and exponentially reinforce the targeted DNA area. Because it can amplify the DNA in very small amounts, PCR is also often used to detect the presence of specific DNA sequences.
DNA sequencing and genomics
DNA sequencing, one of the most fundamental technologies developed to study genetics, allows researchers to determine the order of nucleotides in DNA fragments. The chain-termination sorting technique, developed in 1977 by a team led by Frederick Sanger, is still routinely used to sequence DNA fragments. Using this technology, researchers have been able to study the molecular sequences associated with many human diseases.
Because sorting has become cheaper, researchers have sequenced the genome of many organisms using a process called genome assembly, which utilizes computational tools to unite the sequence of many different fragments. This technology is used to sequence the human genome in the Human Genome Project completed in 2003. The new high throughput sequencing technology dramatically lowers the cost of DNA sequencing, with many researchers hoping to bring the cost of resequencing the human genome up to a thousand dollars.
Sequencing generation (or high throughput sequencing) arises from increasing demand for low-cost sequencing. This sequencing technology allows the production of millions of potential sequences simultaneously. The large amount of available sequence data has created the field of genomics, research that uses computational tools to search for and analyze patterns in the full genome of organisms. Genomics can also be considered a sub-field of bioinformatics, which uses a computational approach to analyze large amounts of biological data. A common problem for this field of research is how to manage and share data relating to human subjects and personally identifiable information. See also genomic data sharing.
Society and culture
On March 19, 2015, a group of prominent biologists urged worldwide ban on the use of clinical methods, particularly the use of CRISPR and zinc fingers, to edit human genes in a heritable manner. In April 2015, Chinese researchers reported basic research results to edit the DNA of human embryos that can not live using CRISPR.
See also
References
Further reading
External links
- Genetics on In Our Time on the BBC.
- Genetics in Curlie (based on DMOZ)
Source of the article : Wikipedia
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