Moderator: Moridin
Биолог с двайсетина години стаж.Marfa wrote:Е кой е авторът на туй чудо?!
- но кохерентно вътре в рамките на обяснението) аналогията с компютрите, даже бих могъл да я пренапиша, преразказвайки някои от фразите (като "хармоничен геном", "освождава се в околната среда", "като вирусите заразяват"), които са създали "конфликти в разбирането". Някой има ли нужда?kalein wrote: Биолог с двайсетина години стаж.
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Пич, някой като иска да оспорва нещо конкретно, нека провери първо преди да скача, нека да прочете как точно става цялото одобрение на ГМО, много е лесно да се говори с генерални изводи като - ти си в грешка, ама аз макар да не съм чел, няма и да се опитам да прочета и да се опитам да докажа че грешиш...passer-by wrote:Itilon ти задава доста конкретни въпроси, ти отговаряш с едно общо и нищонезначещо изречение.Samail wrote:Ще ми се да не беше вярно но е, светът не е толкова перфектен колкото си мислеше, а?
Трудно ще бъдеш приет насериозно ако правиш голи твърдения, а при поискване на доказателства отвръщаш "Ами просто е вярно и точка."
Линкове в подкрепа на това твърдение, моля.Samail wrote:И да спомена щото там може би не го пише, че открито се знае, че цялото тестване на ГМО-та в ЕС се прави от самите ГМ компании, като Монсанто, просто защото никой не смята за нужно че независима експертиза е нужна. Е как да не критикуваш цялата тая лудница тогава?!
<-Подробно описание на нещата, които ми образуват нерви По-специално при растенията:Since the emergence of horizontal gene transfer as a way of explaining phylogenetic incongruence using different gene trees, a considerable number of studies have been published about genes that have been acquired by horizontal gene transfer (Gogarten et al. 2002; Lerat et al. 2005), both in Bacteria (Saunders et al. 1999; Ochman et al. 2000) and Archaea (Doolittle & Logsdon 1998; Faguy & Doolittle 1999), as well as in eukaryotes (Andersson 2005). These studies show that the transfer can occur not only among but also between domains in all possible directions: from Bacteria to Archaea (Rest & Mindell 2003), from Archaea to Bacteria (Gophna et al. 2004), from Archaea to Eukarya (Andersson et al. 2003), from Bacteria to Eukarya (Watkins & Gray 2006), from Eukarya to Bacteria (Guljamow et al. 2007) and even within Eukarya (Nedelcu et al. 2008). However, it is in bacterial and archaeal evolution that horizontal gene transfer has been more widely documented and accepted.
In addition, it has been shown that the acquisition of foreign genes from bacteria and other eukaryotes is also important in fungi (Richards et al. 2006) and plant evolution (Martin et al. 1993; Huang & Gogarten 2008), and has contributed to the evolution of bdelloid rotifers (Gladyshev et al. 2008). On the other hand, horizontal gene transfer in eukaryotic evolution would be even more important if we consider animal and plant hybridization a massive horizontal gene transfer event, as well as the proposed role of hybridization in evolution (Seehausen 2004).
За „дисхармонизирането” на генома (въпреки че цитатът на Калин наистина не е коректен като аналогии): GE = генно инженерствоIntrogression is the movement of a gene or genes from donor plants to sexually compatible recipient plants of a different genotype (e.g., different species, variety, or biotype) by sexual crossing, followed by backcrossing of the hybrid with the recipient population until the gene is stabilized in the population. This process is sometimes called gene flow. Gressel (2002a) points out that there are more confirmed cases of gene flow from weeds to crops than vice versa. Gene flow between plants may occur if the source and recipient plants are grown close enough to each other. Pollen can be carried for long distances by wind, water, insects, and animals, but viability decreases with time and environmental stresses. So, increased distance only reduces, but does not eliminate, the probability of gene flow. Also, to occur, the potential gene source and recipient populations must flower at the same time and must be open-pollinated. For full movement of the gene or genes into another population, several backcrosses are required. Introgression of herbicide resistance transgenes into weedy species has the potential to exacerbate problems with existing weed species in GRCs or to create a new weed problem with species that are normally not a problem.
За това кое би могло да е вредно на ГМО като храна:As mentioned earlier, one of the major capabilities of GE is to introduce genes from sexually incompatible backgrounds. A gene is therefore placed into a new genetic background to which—during evolution—it has not been exposed, nor has the genetic background been exposed to this gene. Is this a serious concern?
The reductionist approach to molecular biology posits that genes can be studied in isolation and that they have discrete and unambiguous effects on the phenotype. This is reflected to a large extent in the current strategy in genomics research where a limited number of (in some cases, one) genotypes are studied. Disruptions of genes either by physical, chemical, and insertional mutagenesis are used to make inferences about the function of the gene. This approach assumes that genes will be expressed regardless of the genetic background and the environment. Likewise, expression analyses by such technologies as microarrays are conducted with limited reference to quantitative approaches. In reality, some genes may only be expressed in certain genetic backgrounds and environments. This lack of consistent expression results in phenotypic plasticity, whereby the same genotype produces multiple phenotypes depending on the environmental conditions (Pigliucci et al., 1999; Sultan, 2000).
Conversely, genetic heterogeneity refers to a situation where different genotypes produce the same phenotype. Although these are widespread phenomena, the molecular, biochemical, and physiological bases are poorly understood. Much of the available information comes from studies on experimental organisms such as yeast, Drosophila, and Caenorhabditis elegans. For example, double mutants have been identified that lead to synthetic lethality, which defines a relationship where the presence of one gene allows the organism to tolerate genetic variation in another gene that would be lethal in the absence of the first gene. For example, some 170 genes have been identified in the protein secretion pathway of yeast into the vacuoles. These and other genes are involved in some 240 synthetic lethal interactions (Hartman et al., 2001). In comprehensive synthetic lethal screens, individual genes interacted with between three and eight genes. These epistatic interactions are by no means unique to yeast, but are general among living organisms and, from a methodological standpoint, can be used to actually determine the order of genes in biochemical and developmental cascades (Avery and Wasserman, 1993). In plants, genes involved in pathogen recognition and response pathways may provide a similar example of genetic buffering through redundancies (Dangl and Jones, 2001).
The available data therefore show that far from acting in isolation, genes act in concert with others and are influenced by the environment. The response of transgenes to environmental influences and the genetic background in which they operate has to be taken into account. It should be pointed out here that these concerns are not limited to transgenes but any genes that are introgressed into crops within the same species or from other species, whether by classical breeding or GE. Examples of these phenomena, observed after transfer by sexual crosses from close relatives, include reversal of dominance, epistasis, and differential sensitivity to environmental conditions of the tb1 gene in maize (Doebley et al., 1995; Lukens and Doebley, 1999) and the effect of epistasis on some traits distinguishing annual species of sunflower (Helianthus spp., Kim and Rieseberg, 2001) and on seed yield in wide crosses of rice (Li et al., 1997; Yu et al., 1997) and common bean (Johnson and Gepts, 2002). These observation immediately raise the question whether introduction of genes from more distant genetic backgrounds, such as might be the case with GE, will be faced with a larger or smaller number of interactions. No answer is available to this question, which may well be faced with difficult experimental difficulties related to linkage drag in sexual crosses. From a practical standpoint, however, testing that normally takes place during the breeding process should eliminate deleterious mutations or underperforming genotypes resulting from these interactions, whether they arise from the introduction of genes via GE or classical breeding.
A corollary of Observation 6 is that the purported speed of introduction of genes by GE compared with classical breeding is overstated. There are three main reasons why the duration of the introduction of new genes is more similar between classical breeding and GE than generally stated. First, the length of the process in classical backcross breeding is not as long as usually presented, other things being equal, especially if it is guided by molecular markers. Crops produced in this way are not considered transgenic because the transfer of genes occurs solely through the usual sexual processes. Classical breeding typically would introduce a single gene by backcrossing. Without molecular markers, at least six backcrosses would be needed. For the average annual crop, this would represent around two calendar years. The use of molecular markers to select for the gene(s) and against the genetic background of the donor parent shortens this introduction by two or three generations so that introduction by classical means can be achieved in somewhat more than 1 yr.
Second, the introduction of genes by GE is faced with uncertainties related to the transgenic nature of the gene introduction (Zhong, 2001). These uncertainties are generally not observed with standard backcrossing. Genetic engineering lacks precision in that the integration point is uncertain. Ideally, the transgene(s) should be integrated in a location of the genome where (i) stable expression and predictable Mendelian transmission is assured and (ii) the expression of endogenous genes is not disrupted or silenced (Iyer et al., 2000; Kunz et al., 2001; Meyer, 2000; Morel et al., 2000). Precise integration of transgenes by homologous recombination, although possible in yeast, is still elusive in higher plants. Additional issues associated with transgenic transfer are stability of gene expression as a function of the environment and the point of integration into the genome ("position effect"). Thus, the initial introduction of transgenes have to be followed by extensive progeny testing to identify those integration events that are consistent with a high level of stable expression, which further reduces the supposed time advantage of GE. An example of the intensive testing to be conducted following transformation is provided by the case of glyphosate-tolerant line 40-3-2 of soybean (Padgette et al., 1995) for which seven generations were needed to verify stability and level of expression by classical breeding procedures. These pitfalls in transgenic methodology and potential solutions are discussed in greater details in a recent review (Zhong, 2001). Potential solutions to these problems have been proposed (reviewed in Allen et al., 2000; Chandler and Jorgensen, 2000; De Wilde et al., 2000; Hohn and Puchta, 1999; Kumar and Fladung, 2001).
Thirdly, current genetic engineering methods are generally genotype dependent. Often the genotypes used for GE are not elite genotypes used in the development of new cultivars. Therefore, successful transformation has to be followed by a classical backcross program to introduce te transgenes into the desired genetic background. These additional backcrosses, even when aided by marker-assisted selection, represent an additional time cost.
A good example of the need to breed the transgene (i.e., getting it into improved genetic background) is currently happening with herbicide resistant soybean developed through GE. The first wave of herbicide resistant soybean varieties proved to be very susceptible to Sclerotinia stem rot [cause by Sclerotinia sclerotiorum (Lib.) de Bary]. Through necessity, the genetic background of the germplasm chosen for transformation was very narrow and proved to be highly susceptible to S. sclerotiorum. As a result the GE herbicide resistant varieties showed increased susceptibility to Sclerotinia stem root because of their genetic background but not as a result of the introduction of the transgene or any sensitivity to the herbicide (Lee et al., 2000).
In summary, selection for the transformation events with the highest and most stable expression will require multilocation, multiyear testing, making GE more akin to classical breeding. In addition, testing for the possible disruption of existing developmental or biochemical pathways also takes time, especially if the introduced genes come from a widely different genetic background. It is likely that technical advances will advance the precision of genome insertion and the stability of expression of transgenes. In turn, these advances will increase the speed of GE in generating new genotypes.
A transgene might pose a food safety risk for two basic reasons. First, the transgene protein product itself could be toxic, due to direct toxicity, anti-nutritive effects, or allergenic effects. Second, the gene could cause a change in the metabolic pathways of the crop changing the levels of already existing metabolites or introducing a new metabolite. The latter risk can be due either to a direct effect of the transgene product or to insertion into the genome at a place that alters expression of other genes.
Това ще го приема като комплимент - нямаш представа колко неща не са ми ясни и ги научавам в движение :)thorn wrote:.......Това, че на теб са ти ясни нещата, не значи, че с всички други е така. .........
A genome-integrated hepatitis B virus DNA in human neuroblastoma*1
Nailya E. Tagieva**, Rinat Z. Gizatullin, Vladimir M. Zakharyev and Lev L. Kisselev,
Engelhardt Institute of Molecular Biology, 117984, Moscow, Russia
Received 30 June 1994; revised 8 July 1994; accepted 26 September 1994. ; Available online 23 December 1999.
It is known that hepatitis B virus (HBV) DNA is capable of integrating into host genome (reviewed by Buendia, 1992). Recently, it has been assumed that HBV affects many human cell types in addition to hepatocytes (Dejean et al., 1984; Harrison, 1990). Among children with lymphoid and solid tumors the HBV markers are much more frequent than in control groups (Tabor et al., 1978, Vergani et al., 1982). Naumova and Kisselev (1990) have described a considerable prevalence of HBV markers in children with embryonic tumors and in their parents. Furthermore, DNA from the fresh embryonic tumors (neuro- and nephroblastomas) were tested by blot hybridization analysis with HBV DNA. In six out of nine tumors HBV DNA has been found.
Марфа, идеята ми беше, че аз няма хиляда часа да се ровя да търся пак това на което съм се натъкнал преди, затова трябваше да мина с този цитат, който според теб е аматьорски, макар че самият цитат не дава никакви количествени данни които да трябва да доказва, а просто те кара да се замислиш. Който не ми вярва, ми хубаво, аз повтарям, нямам време да върша черната работа на други и да им търся сам референциите, като хората които искат да ме оборят ги мързи ще си прехвърляме ей така топката, и всеки ще казва че другият е грешен, като мен никак не ме е еня...Marfa wrote:Така. Ще бъда пределно ясна. Преди да дадеш в подкрепа на мнението си нещо повече от цитати от интернетен шум, няма да скачаш и няма да говориш с генерални изводи, вадейки подкрепата си единствено пак от средите на интернетния шум. Конкретно цитатът, който си извадил, е забележителна глупост.
Естествено, че когато някой иска да внедри свой продукт на пазара, бил той генномодифициран или не, ще представи на съответните контролни органи изследванията си върху безопасността на продукта. Оттам нататък от съответните контролни органи и от законодателството на конкретната държава зависи дали ще се доверят единствено на това мнение или пък ще се допитат и до свои експерти.
Това пък: "А пък тези фирми имат интерес мутациите да навлизат все по-далеч. Също прозаична причина: ГМО се патентоват. Да, правилно прочетохте, жив организъм подлежи на патент." - те това е директно в мутацията.
Първо, очевидно някой тук не е наясно що е то мутация. Второ, не е наясно, че мутацията като такава не е непременно нещо зло. Трето - това за живият организъм, който подлежал на патент - ами ще подлежи бе! Аз ако произведа единствено чрез селекция, а не чрез генна модификация, многогодишна и издръжлива на ниски температури петуния, няма ли да имам моралното право да я патентовам и да я продавам на любителите-градинари? Ще имам ли? Нали ще имам? Да виждаш нещо нередно в това?! А ако случайно виждаш, можеш да ми обясниш защо патентоването на някакъв зарзават е по-нередно от патентите върху лекарства. Четвърто, фирмите - производители на ГМО нямат интерес от разпространението на мутации, а имат интерес, финансов естествено, да, колко ужасно, от разпространението на собствената си продукция. За това що е мутация и пр. ще оставя сам да прочетеш, защото след хармоничния геном и излъчването на активни гени от ГМО-тата, които действали като вируси и евентуално ще ни заразят с царевица, частни уроци по биология 10 клас не ми се дават към момента.
И за да затвърдим. Когато говориш за доста експерти, които смятали не знам какво си, ще даваш адекватна подкрепа за мнението си, която е различна от публикация, в която се казва, че доста експерти смятали не знам какво си. Тоест или, колкото и да ти е неприятно, ще се правиш на библиотека и ще прилагаш аргументи към спора различни от "намери си сам", или няма да спориш. Въпроси?
Ако се питаш защо - голяма част от хората в този форум имат над средното ниво на познание по биология, а някои разбират и от генетика достатъчно, за да не изпадат в паника всеки път щом някой патентова патладжан.
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Интернетен шум - линкове, които водят към статии, в които се казва, че има изследвания, според които не знам какво и има учени, според които не знам си що, без да се цитират нито самите изследвания, нито самите учени, нито нещо друго, което да разграничи написаното от нещо чуто във фризорския салон.
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