Stops, Frisks, and Terry Stops Research Paper Example | Topics and Well Written Essays - 3750 words

Stops, Frisks, and Terry Stops - Research Paper Example This paper will analyze the Terry stop legal issue and its impact in the society. The paper will also look at constitutional issues that touch on the matter and the impact that they have had. Introduction The issue of stop, frisk and Terry stop is very controversial and has been debated for a long period of time. A Terry stop involves stopping of an individual by a law enforcement officer for frisking and in some cases a short detention. An individual may be stopped for frisking if they are suspected of having committed or being likely to commit a crime by a law enforcement officer. As one undergoes a Terry stop, the police officer frisks and individual (the suspect) to ensure that the officer is not in danger or other members of the public (Acker & Brody, 2012). A Terry stop is different from an arrest since it takes less time and is accompanied by less legal procedures. During a Terry Stop, a police officer usually confirm the details of the suspect and finds out whether they have a criminal record or outstanding fines or arrest warrants that have been issued against them. Groups that represent both sides of the argument present their debates which sound justified. Records of crime statistics show that there has been an increase in crimes that are committed all over the country. People all over the world feel that is up to the government to introduce measures that lead to a reduction of crime levels. Stop, frisks and Terry stops is one of the ways that was introduced by the government to try and curb crime levels all over the country. Law enforcers feel that prevention of crimes consumes fewer resources and saves more lives for minimal inconvenience if any to those that undergo the Terry stops. Discussions Stops, Frisks, and Terry Stops affect many individuals in the United States and perceptions on the government and law enforcement officers. This constitutional issue also affects the constitutional rights of individuals. Terry stop and frisk involves detent ion by police if they are suspicious that an individual has been involved in committing a crime. The Terry stop and frisk law was introduced in 1968 after the Terry v. Ohio, 392 U.S 1 (1968) court decision that was made by the Supreme court in the United States. The decision also authorized the police to conduct searches on the outer garments of the suspect if they have articulable suspicion that the suspect is armed and dangerous. The court authorized law enforcers to being able to detain an individual who they suspect is involved in committing a crime. Law enforcement officers also have the legal right to search the individual that they have detained. In some cases, the law enforcers might feel that the suspect might be in possession of a weapon, and may be planning to use in order to commit a crime. The rationale that causes the law enforcers to feel that the individual is likely to commit a crime should be reasonable. For example, a suspect might look overly nervous yet there is no evident reason why they should appear so. Such behavior might be an indication that such an individual is about to commit a crime. The law authorizes police officers to seize any form of contraband that they would find on a suspect while conducting the frisking. However there are some conditions in the frisking of the suspect (Acker & Brody, 2012). The frisking should be limited to the outer clothing of the

Criminal Law Liability Essay Example | Topics and Well Written Essays - 3000 words

Criminal Law Liability - Essay Example There is also the legal duty to act because of an actual or implied contract. For example, in R. v. Pitwood (1902)2 a defendant was convicted of manslaughter after he failed to close a level crossing gate with the result of a hay cart and a train colliding. The collision resulted in the death of a man. Pitwood argued that he had no legal duty to the deceased, but Judge Wright held that he did have one arising from his contract of employment. While R. v. Pitwood is often regarded as a classic case of criminal liability for omission, Wright's actual words leave some room for doubt: Thus the judge may actually have been seeing liability coming from the fact that Pitwood had left the level crossing gate open rather than the fact that he had not shot the level crossing gate. Thus did the liability come from an action or an inaction It would seem that the former occurred. This was a case of gross negligence manslaughter, a crime that is a useful background to the whole subject of criminal liability for omission. In general such manslaughter requires the following elements: Duty is imposed by common law statute. ... A breach is the failure to do something or doing something incorrectly according to the standard expected. The causal link is the fact that death has resulted from this failure with no intervening cause while gross negligence is the fact that the standard of performance or non-performance is so bad as to make it criminal. A "reasonable person" standard can apply when there is no actual contractual arrangement. Thus if a 'reasonable person" would have acted in a manner that would have prevented or avoided the resulting damage/injury then the defendant may be found liable. For example, in R. v. Miller4 (1982) a defendant was held liable for criminal damage to a building that had been caused by a fire. Miller was a tramp who had fallen asleep in a disused property while smoking a cigarette. The cigarette fell onto the mattress he was asleep on, and when he woke up because of the smoke, Miller did not attempt to put the cigarette/smoldering out but merely moved to another room and fell asleep. The court found that Miller was bound to act because the dangerous circumstance had been of his own making, and the omission that had subsequently occurred was of a criminal nature. By contrast, if Miller had been a person passing by the house and had seen it smoldering but had done nothing he would not have had a duty to put the fire out and thus the other elements of the crime would be irrelevant. Miller, as well as Pitwood also brings up a problem that has yet to be fully resolved regarding criminal liability for omission. The problem revolves around the fact that a general principle of criminal law is that the mens rea of the offence must exist at the time of the actus reus. Essentially there must be a coincidence of the actus reus and the mens

Solve equations and word problems Speech or Presentation

Solve equations and word problems - Speech or Presentation Example Thomas had a checking account there for 8 months and was charged $53.10 in service charges. How many checks did he write during that period? Geometry; Dave and Jane wells have a new rectangular driveway. The perimeter of the driveway is 168 feet. The length is 12 feet longer than three times the width. What are the dimensions of the driveway? Geometry; a leather coin purse has the shape of a triangle Two sides are equal in length and the third side is 3 centimeters shorter than one and one-half times the length of the equal sides. The perimeter is 28.5 centimeters. Find the lengths of the sides Health Club Memberships: In 2006, the number of Americans who were members of a health club was 42.7 million. This was an increase of 106% from the number of health club members in 1990. How many Americans were health club members in 1990?(Source: www.emaxhealt h.com) The Clarke family went sailing on a lake. Their boat averaged 6 kilometres per hour. The Rourke family took their outboard runabout for a trip on the lake for the same amount of time. Their boat averaged 14 kilometres per hour. The Rourke family travelled 20 kilometres farther than the Clarke Family. How many hours did each family spend on their boat

Teaching Reading to Students with Learning Disabilities Essay

Teaching Reading to Students with Learning Disabilities - Essay Example The development of effective reading strategies can have positive consequences for students with learning disabilities, yet many students do not learn to use strategies automatically. Finally, the implications for reading instruction for students with and without disabilities in inclusive settings are discussed. The ability to read is a critical component of school success. A strong correlation exists between poor reading ability and school failure, and students who do not learn how to read during their elementary years have difficulty navigating the school curriculum during middle and upper grades (Marston, Deno, Dongil, Diment, & Rogers, 2005). The National Center for Education Statistics reported that more than 75% of all fourth graders and eighth graders scored below the reading proficiency range on the most recent National Assessment of Educational Progress (NAEP) reading assessment (U.S. Department of Education, 2002). These numbers suggest that a large number of students with and without disabilities are not benefiting from current traditional reading curricula and instructional practices (Carnine, Silbert, & Kameenui, 2001; Simmons & Kameenui, 2000). Improving reading instruction is a top priority for both general and special education. These concerns are paramount for students with high-incide... Among the students with high-incidence disabilities, children classified with learning disabilities constitute the largest group of students receiving special education services. More than 2 million students in the United States are classified with a learning disability, a number that has increased dramatically since the late 1970s. In the past decade alone, the number of students classified with a learning disability increased 38%, and currently students identified with a learning disability represent 51% of all students with disabilities (U.S. Department of Education, 2000). The 2001 reauthorization of the Individuals with Disabilities Education Act (IDEA) specifically identified the general education setting as the most appropriate placement for all students, and about half of the students classified with a learning disability participate full time in a general education classroom. Full-time placement in the general education classroom is commonly called inclusion or inclusive education (U.S. Department of Education, 2000). In inclusion settings, students with disabilities may or may not receive additional support from a special education teacher. Some programs involve general and special education teacher collaboration, but in many cases the general education teacher is responsible for implementing all academic support services, curricular adaptations, and testing modifications (Schulte, Osborne, & Erchul, 2002). Moreover, most new standards-based reform initiatives require that students with learning disabilities meet minimum local and state competenc y requirements. Despite the extra responsibilities this places on teachers, many school districts continue to reshape the roles of

Amelie - Intercultural Film Review Essay Example for Free

Amelie Intercultural Film Review Essay Amelie is a French movie about a young twenty something girl who’s world opened up to her when her mother dies and she is allowed to venture out. After a health misdiagnoses at a young child Amelie is stranded in her home away from all people and relationships until her mother passes away and she finds herself free. She becomes a waitress and decides to help all the people around her until one day she herself finds love. This film shows a French cultural pattern where the people are open minded, whimsical, unique, and quirky. The main character Amelie, wants to get the most out of her life. She takes the viewer on a path through a series of subplots where she is trying to help people that surround her find happiness and joy. Paris and the people of France are shown in a whimsical and fairytale environment. All the while, Amelie, is removed from all human contact which makes for an interesting film if one is attempting to view this film through the lens of interpersonal communication. All the communicating in the movie is done through the use of metaphors, scheme, plots, tricks, and the like. It’s interesting because Amelie doesn’t directly communicate with people even though she is not anti-social. She is very social and likes to help people but she does so almost exclusively nonverbally. One exception to this is when Amelie helps a blind man to cross a busy street and, opposite to her normally silent nonverbal character, she proceeds to very quickly describe everything that she sees and everything that is happening to the blind man in exceptional detail. This is done as an act of kindness for someone who can’t see and not as a form of actual or real communication. All real communication in this movie, is done in a childlike fashion of cat and mouse. It feels almost like interpersonal communication in this movie is a game that is not to be taken seriously. When Amelie finds a boy that she is romantically interested in, she finds herself needing to communicate with him only from a distance. Amelie once again plays one of her games in order to conceal her identity. Nino, the object of Amelie’s affection, is a boy who collects old photos from an old photo booth. The use of pictures in this movie is overwhelming and must have some reason behind it. Itâ€℠¢s almost as if the characters are communicating through the pictures rather than with words. Even when Amelie was quickly describing the surrounding to the blind man she was helping across the street, it was as if she was creating a picture in his mind so he could connect with her. Perhaps Amelie can only  communicate through imagery like metaphors and photographs because she spent her entire childhood alone with only her parents because they thought she was too ill to be around others. I have mixed feelings about this film because I can appreciate a good romantic comedy and I understand the feeling the director was trying to create but I’m not a fan of the fanciful fairytale romances which I think this movie falls into. I would have preferred a movie with a real underlining tone and I could do without all the whimsy. Amelie felt like a child in a woman’s body, not unlike 13 going on 30 ¸ and for me the doe eyed cutesy character began to wear on me and I found myself more annoyed than anything by the end. The setting is Paris, but not the real Paris but rat her a fantasy version of Paris not unlike a dream or the Paris you can see in old movies. The story itself felt very Disney-like in that the mother dies in the beginning which is the impetuous to the main character being forced unprepared onto the world, the main character then helps many sub-characters out along the way to finding her true love. Very Disney indeed. I’m certain that I would not recommend this movie to my friends or my family, but maybe it would have a place in a cultural communications classroom. I think the only problem I would have with it is that it doesn’t portray an actual or real culture, and only portrays a fantasy like culture. The lead character is able to form relationships and make the audience care about her without having to say much at all, which can have some value when it comes to the study of nonverbal communication. Also, there might be a value to getting a feel for the French culture from this film, because even though I didn’t love the story or the film-making, there was something about the ‘sound’ in the film. The dialogue did draw me into the French culture which was interesting because I don’t speak any French. Even though I struggle to pinpoint the feeling or atmosphere of the film, I do think that something was captured even if it was just the Disney version of Paris and French Culture.

Improving Concordance to Smoking Cessation Treatment

Improving Concordance to Smoking Cessation Treatment National Institute of Clinical Excellence (2009) identified that medicine taking is a complex human behaviour that lies ultimately, in the hands of the patient. NICE (2009) estimates that between a third and a half of all medicines prescribed are not taken as recommended and Dunbar-Jacob et al (1995) evaluates that up to 80 per cent of patients can be expected not to comply with their treatment at some time. Shuttleworth (2006) noticed that health professionals use two terms to describe the medicine taking behaviour of patients: compliance and respectively adherence. Compliance represents the extent to which a persons behaviour coincides with the medical advice, for example patients to do as they are told (Haynes et al, 1979) while adherence is the capacity of the patient to self-regulate his or her treatment, for example his or her ability to re-fill prescriptions (Brock, 2000). Medicines Partnership (2003) argue that in both compliance and adherence patients have a passive role, with no implication in their care and therefore concordance is needed to correct issues of non-compliance and non-adherence. Concordance advocates the idea of shared decision-making between health professionals and patients and it requires health professionals to engage with patients as partners, taking into account their beliefs and concerns (Medicines Partnership, 2003). NICE (2009) insists that the biggest challenge of the research of concordance is how to influence and change behaviour and this is where health psychology comes in. According to Marks and Evans (2005) health psychology attempts to move away from a linear model of health that treats only the physical, to a model that treats the whole person including his or her behaviour. In this essay the author will critically discuss how knowledge of health psychology can help nurses improve concordance with treatment in smoking cessation treatment. The idea promoted is that smoking is a behaviour influenced by the patients beliefs; the nurse will explore the patients beliefs on smoking and will help the patient to make an informed decision regarding her treatment. Patient X will be used as an example to observe behaviour change. The Stages of Change Model and other theories from health psychology will also be discussed. Discussion: Health Development Agency (2004) estimates that smoking is the greatest single cause of preventable illness and premature death in the UK, being responsible for more than 106,500 deaths each year. Approximately 4000 chemical compounds have been identified in the cigarette smoke, of which 40 are known to cause cancer (McEwen et al, 2006). Among these compounds tar was linked to cancer, lung disease and heart disease; carbon monoxide (CO) was also identified as an inevitable consequence of the combustion that takes place while smoking (Tyler, 1995); furthermore, nicotine was found in cigarettes, however nicotine is not connected to cancer but with the addiction process. According to the RCPÂ  [1]Â  (2000) nicotine meets all criteria used to define a drug of dependence and Wilkinson et al (2004) reasons that this makes smoking not a habit but an addiction. In the light of these, nurses face a real challenge when trying to improve patients concordance with smoking cessation treatment. However, NIHÂ  [2]Â  (2008) urges that most patients are ready to hear and receive help from nurses as the patients willpower alone has been shown to succeed in only 3 per cent cases of smoking cessation (McNeill et al, 2001). The following scenario will be used to exemplify a nurses action and use of health psychology knowledge in helping improve a patients concordance with smoking cessation treatment: Patient X is a bank manager. She has been a smoker for ten years. She is married and has one child age 5. She doesnt want to stop smoking because smoking calms her nerves, because it is not a good time and because she is afraid of withdrawal symptoms and gaining weight. The nurse will use the Transtheoretical Stages of Change Model to assess patients X motivation. The model was developed by Prochaska and DiClemente in 1982 to examine the five stages of change in addictive behaviours. According to Odgen (2009) the model is dynamic, not linear, with individuals moving backwards and forwards across the stages. The first stage of the model is Pre-contemplation. Patient X was identified as being in this stage because she is not interested in quitting. McGough (2004) points out that sometimes beliefs are used to sustain unhealthy behaviours, for example cigarettes calm my nerves, as patient X claims. To address such health beliefs and her resistance to change, the nurse will use a consciousness raising exercise, respectively she will address patient X reasons for not quitting and give counterpoints to refute these reasons (Perkins, Conklin and Levine, 2007; Kaufman and Birks, 2009). For example, patient X states that it is not the right time; the nurse can address this by saying, Im concerned about your health and I would like you to consider quitting. I know its going to be difficult because it will interfere with life responsibilities however, the perfect time to quit may never come therefore this moment is as good to quit as any (Perkins, Conklin and Levine, 2007; Hollis et al, 2003; Rana and Upton, 2009). TMAÂ  [3]Â  (2008) suggests that such message can prove more effective than a lecture about the lung cancer however the nurse can have a stop smoking handout to give to the patient as well. This interaction with the patient must be kept as patient-centred as possible to improve concordance with treatment (Walker, J et al, 2007). Balint et al (1970) as cited in Rena and Upton (2009) suggest that being patient-centred should involve the asking and receiving of questions and information which result in patients understanding of the health information and the treatment proposed. An accurate assessment of patient X within this stage will generate a strong treatment plan, therefore improved concordance (Straub, 2006; Brock, 2000). Furthermore, the nurse will convey warmth, understanding, acceptance and respect for the patient; this will help develop a fundamental nurse-patient relationship that is seen as a contributing factor to the patients concordance with the treatment regimen (Rana and Upton, 2006; Donohue and Levensky, 2006). By learning that smoking is not good for her health patient X will move to the second stage of the Stages of Change Model called Contemplation. The patient is now aware of the health risks that smoking entails and contemplates the idea of quitting (Perkins, Conklin and Levine, 2007). At this stage motivational interviewing can be used by the nurse to allow the patient to discover her own internal motivating factors in the favour of quitting; examples of factors can be: my five year old child will grow in a smoke free environment or I will have less changes of getting cancer (Ogden, 2009; NIHÂ  [4]Â  , 2009). Furthermore, the nurse can suggest that patient X writes down as a reminder I lose these benefits every day that I do not quit smoking (Connors, Donovan and DiClemente, 2004). Moreover, the nurse can help patient X identify the pros and cons of smoking cessation treatment (Hollis et al, 2003). According to the Health Belief Model (HBM) (Rosentock, 1974 as cited in Rana and Upton, 2009) by weighing the pros and cons of treatment, people arrive at a decision of whether the perceived benefits (e.g. NRTÂ  [5]Â  ) outweighs the perceived barriers (e.g. being afraid of the side effects of NRT). Moreover, patient X is concerned that she may gain weight upon quitting. By still using the HBM the nurse can help the patient decide whether the perceived benefits of quitting (e.g. improved health) outweighs the perceived barriers (e.g. gaining weight) (Perkins, Conklin and Levine 2007). The HBM is a social cognition model that has been applied to understand adherence behaviour in patients. This model suggests that the likelihood that someone will engage in a given health behaviour (e.g. adherence) is a result of four functions: perceived susceptibility, perceived severity, perceived benefits and cues to action (Rena and Upton, 2009). In an argument against HBMs application to smoking cessation, Robinson and Beridge (2003) state that weighing pros and cons of smoking cessation treatment is not a reliable approach because the smoking behaviour is underlined by addiction, so that it operates outside conscious awareness and it does not follow decision-making rules. Perkins, Conklin and Levine (2007) agree that the motivational intervention used in the contemplation stage may push the person into the third stage of the Stages of Change model, called Preparation. The patient is now determined to make a change. Both the nurse and patient X will share a decision making over preparation strategies; the outcome of this partnership will be a patient-centred, tailored plan that will improve adherence. For example, a nicotine patch may indeed help patient X to quit smoking, but a patient Z who not only has nicotine patches but also told his family and colleagues (especially those who smoke) about his quit attempt and ask for their support, is likely to be more successful than someone who relies on nicotine patches and willpower alone because social support enhances the likelihood of adherence (TMA, 2009; McEwen et al, 2006; Medicines Partnership, 2003). Furthermore, patient X will be encouraged to set a quit date. The chosen date should be of significance for the patient so she can feel motivated to adhere to the treatment (Gross and Kinnision, 2007). Moreover, the nurse may suggest behavioural changes such as clearing the house of all cigarettes and lighters (Marinker and Shaw, 2003). Patient X will also be educated to recognize withdrawal symptoms and will be given tips on how to resist cravings (e.g. keep busy, eat fruits, sip water, call a helping friend); patient X will be re-assured that withdrawal symptoms last 2-4 weeks and reduce gradually; also, the nurse must introduce patient X to medication that can help reduce the severity of the withdrawal discomfort, such as NRT and Bupropion (McEwen et al, 2000). According to NICE (2009) the information about medication should be written to serve as a reminder at any stage of the treatment. Moreover, the patient will be shown how to use nicotine patches and gums because in this stage specific skills rather than motivation alone are needed to facilitate concordance with treatment (Gross and Kinnison, 2007; Thomason, Parahoo and Blair, 2007). Furthermore, the nurse will answer any questions that the patient may have regarding medication. The Royal Pharmaceutical Society (1997) as cited in Rana and Upton (2009) suggests that how individuals perceive and think about medication (medication belief) is important when considering treatment adherence, therefore the nurse should be aware of patients X medication beliefs if she wants to break the barrier of non-adherence to treatment. Patient X is now considered ready to move into the penultimate stage of the Stages of Change Model called Action. At this stage, the nurse must provide on-going support to prevent the patients relapse. The nurse is encouraged to be honest with patient X about the likelihood of reverting to the old behaviour once the change process has started, not because the nurse expects patient X to fail, but because it normalizes the experience and takes away some of sense of failure and shame (Singer, 2009). The nurse will also monitor patient Xs CO and saliva cotinine to confirm abstinence and boost motivation (Haskard-Zolnierek and DiMatteo, 2010). According to the Foundation for Blood research (2010) many patients may not be truthful when answering questions about their smoking behaviour, therefore tests such as measuring the amount of nicotine in saliva and the amount of carbon monoxide levels in the patients expired air can be useful to compare self-reported smoking behaviour against real measurements. In an argument against this, Riemsma et al (2003) state that there is no evidence that moving an individual closer to the action stage actually results in a sustained change of behaviour at a later date. After approximately six months in the action stage patient X will move to the last stage of the Stages of change model, the maintenance stage. The nurse will praise the patient for the efforts made to change the unhealthy behaviour into a healthy one. This will make the patient feel self-efficient and have confidence to maintain the behavioural changes done in the quitting process (Odgen, 2009; NIH 2009). Self-efficacy is a term introduced by Bandura (1997) as a cognitive mechanism underlying behavioural change. According to this theory, efficacy determines whether coping behaviour is initiated and maintained when faced with obstacles (e.g. nicotine cravings) (DiClemente, 1981). Furthermore, the nurse can also write down essential tips to help patient X maintain concordance with treatment, such as do something else instead of smoking, keep yourself busy, avoid tempting situations and stick with your effort to quit, you can do it (Johnson et al, 1999; NIH, 2009). Conclusion: To review, within this essay the author highlighted the ideas that knowledge of health psychology can be used to understand the patients smoking related health beliefs and also, improved concordance with smoking cessation treatment can be achieved by involving the patient as partner in care.

Bacterial Artificial Chromosomes (BACs) Features

Bacterial Artificial Chromosomes (BACs) Features Definition: Bacterial Artificial Chromosomes or BACs are plasmids (circular DNA molecules) constructed with the replication origin of E.coli F’ Factor. F’ is an incompatibility group involved in E. coli conjugative ability and chromosomal transfer, which can exist as an extra-chromosomal element. 1st developed as a large insert cloning system to facilitate the construction of DNA libraries to analyze genomic structure. Technology was developed to carry out genetic and functional studies of viruses (herpes virus especially). Since then BACs application have grown intensely and have benefited the research community in many fields, such as in genomic fingerprinting, sequencing of the human genome, in vaccine development and in vitro transgenesis,. Characteristic features of BAC vectors The original BAC vector, pBAC108L, is based on a mini-F plasmid, pMBO131 (Figure 1) which encodes genes essential for self-repli ­cation and regulates its copy number inside a cell. The unidirectional self-replicating genes are oriS and repE while parA and parB maintain copy number to one or two for each E. coli genome. Multiple cloning sites is present, flanked by â€Å"universal promot ­ers† T7 and SP6, all flanked by GC-rich restriction enzyme sites for insert excision.   Presence of cosN and loxP sites(cloned in by bacteriophage l terminase and P1 Cre recombinase, respectively) permits linearization of the plasmid for convenient restriction mapping. There is a chloramphenicol resistance gene for negative selection of non-transformed bacteria. Vector is 6900 bp in length and is capable of maintaining insert DNA in excess of 300 kilobases (kb). Other BAC Vectors There have been many modifications done to increase the ease-of-use as well as for use in specific systems and situations.   pBeloBAC11 2 and pBACe3.6 are modified BAC vectors based on pBAC108L and are commonly used as a basis for further modification. pBeloBAC11 The primary characteristic of this vector is the addition of a lacZ gene into the multiple cloning site 2 of pBAC108L. Plates supplemented with X-gal/IPTG, an intact lacZ gene encodes b-galactosidase which catalyses the supplemented substrate into a blue substance. Successful ligation of insert DNA into the vector inactivates lacZ, generating white colonies, indicating the presence of a successful vector-insert ligation. It is still a low-copy number plasmid due to presence of parA and parB. Size of vector is 7507 bp in length. pBACe3.6 This vector is based on pBAC108L but is more highly modified than pBeloBAC11. In order to overcome the issue of low plasmid copy numbers, the P1 replicon in F’ was deleted and a removable high copy number replicon originating from an inserted pUC19 was introduced.   This vector contains 2.7 kb pUClink stuffer fragment which is flanked by two sets of six restriction sites within a sacB region. Levansucrase, a product of sacB gene, which converts sucrose (sup ­plemented in the media) to levan, which is toxic to E. coli host cells. Hence, if the vector is re-ligated without an insert, the functional sacB produces levansucrase and the cells die before forming colonies. Successful ligation of an insert into the vector increases the dis ­tance from the promoter to the coding region of sacB, disrupting toxic gene expression in the presence of sucrose. In addition to this vectors, there are many specialized BAC vectors carrying a variety of different combinations of drug resistance genes. Besides, many different selection mechanisms and markers are available. Modifications of cloning sites (unique restriction endonuclease sites) are also common as per the addition of genes and promoters specific to different strains of bacteria. Development of BAC vector Advantages of BAC Vectors The large size of BACs help to minimize site of integration effects, a phenomenon which has been defined as endogenous sequences (such as gene coding regions and distal regulatory elements) to be disrupted, and to produce potentially undesirable phenotypes in gene cloning technology. Endogenous gene expression more accurately than other cloning systems. The human genome BACs consist of the full gene structure(which play very important role in gene regulation). Therefore the human genome BACs will ensure full mRNA processing and splicing when genes are transcribed, and produce the full complement of protein isoforms once mRNAs are translated. It can be transfected and expressed in mammalian cell lines even if transfection efficiency and copy numbers are low. Disadvantages of BAC vectors A construct containing a large genomic fragment is likely to contain non-related genes which may lead to indirect, non-specific gene expression and unanticipated changes in the cell phenotype. Recombinant BAC constructs can be time-consuming and labor-intensive. The large size BAC DNA constructs are more easily degraded and sheard during manipulation before transfection. Applications of BAC vectors BACs are useful for the construction of genomic libraries but their range of use is vast. It spans from basic science to economically rewarding industrial research, and fields as prosaic as animal husbandry. In genomic analyses, it helps in determining phylogenetic lineage det between species. Helps in study of horizontal gene transfer and since bacterial genes are usually clustered, the ability of BAC vectors to accommodate large inserts has allowed the study of entire bacterial pathways. By isolating DNA directly from soil or from marine environments, the â€Å"metagenomes† of those organisms which are either uncultureable or are termed viable but uncultureable can be cloned into BAC vectors and indirectly studied. In industrial research fields where BAC vectors are invaluable tools in cataloguing novel genomes is in the discovery of novel enzymes. Work has been done on identifying enzymes that are involved in biopolymer hydrolysis or even radioactive waste management. BAC vectors have been instrumen ­tal in studying large double stranded DNA viruses both from an academic point of view and as a tool to develop improved vaccines. In genomic research, high throughput determination of gains and losses of genetic material using high resolution BAC arrays and comparative genomic hybridization (CGH) have been developed into the new tools for translational research in solid tumors and neurodegenerative disorders. BAC technology is becoming the most upcoming method for genome sequencing. The technique uses an overlapping tailing part of large genomic fragments (150-200 kb) maintained within BACs. Every individual BAC is shotgun sequenced, where these large overlapping sequences of the BACs are assembled to produce the whole genome sequence. BACs have also been used in mammalian genome mapping, genomic imprinting, vaccine development, gene therapy and studies of the evolutionary history and functional dynamics of sex chromosomes have recently been possible using BAC libraries. YAC (yeast artificial chromosome) vectors Definition: Yeast artificial chromosomes (YACs) are plasmid shuttle vectors capable of replicating and being selected in common bacterial hosts such as Escherichia coli, as well as in the budding yeast Saccharomyces cerevisiae. They are of relatively small size (approximately 12 kb) and of circular form when they are amplified or manipulated in E. coli, but are rendered linear and of very large size(several hundreds of kilobases), when introduced as cloning vectors in yeast. Many different yeast artificial chromosomes exist as ongoing refinements of the initial pYAC3 and pYAC4 plasmids (Figure 1) constructed by Burke et al. (1987). Basic structural features of YACs were developed from the yeast centromere shuttle-plasmids (YCp) series. These are composed of double-stranded circular DNA sequences carrying the b-lactamase gene (bla) and the bacterial pMB1 origin of replication, thus conferring resistance to ampicillin and the ability to replicate in bacteria, respectively. YACs also contain the cloning site in the middle of the SUP4 suppressor of an ochre allele of a tyrosine transfer RNA gene; this enables restoration of the normal white color phenotype in otherwise red ade1 and/or ade2 nonsense mutants. Accordingly, in the insertional inactivation cloning process, the SUP4 gene is disrupted by the DNA insert, thus removing the suppression of the ade mutations and allowing their phenotypic expression as red color. They also include yeast ARS1 with its associated CEN4 DNAsequence, as well as the URA3 selectable marker. Biological Features of YACs The stability of YAC vectors in yeast per se is similar to that of natural chromosomes provided that all three structural elements (ARS, CEN and TEL) are present and functional, in addition, that the minimal required size is reached by the insertion of enough exogenous DNA. Indeed, several mutations are known to affect YAC stability and segregation together with natural chromosomes. Another important consideration is that faithful duplication of YACs is guaranteed only if other DNA sequences incompatible with ARS do not exist on the construct, particularly relevant when unknown DNA inserts are cloned in the YAC vector, as in the case for genomic libraries, in which there could be cryptic or otherwise unknown ARS-like sequences able to interfere with the ARS function. Construction of YACs Steps: Initially, purification of plasmid DNA is carried out. Two distinct digestions are performed: the first with BamHI that cuts twice adjacent to the two telomeric DNA sequences flanking the HIS3 gene, which therefore is excised from the plasmid and lost (Figure 2a). This first digestion generates a long linear fragment carrying telomeric sequences at each end. The second digestion consists of the opening of the cloning site within the SUP4 gene (Figure 2a). As a result of this second digestion, two linear fragments are produced as left and right arms of the future linear YAC (Figure 2b). Large DNA fragments with ends compatible to the cloning site, obtained from the desired genome source by digestion with an appropriate restriction endonuclease, are ligated with phosphatase treated YAC arms, to create a single yeast-transforming DNA molecule (Figure 2c). Primary transformants can be selected for complementation of the ura3 mutation in the host, and successively for complementation of the host trp1 mutation, thereby ensuring thepresence of both chromosomal arms. Transformant colonies containing the exogenous DNA insert within the SUP4 gene are detected by their red colour, due to the inactivation of the suppressor activity and the consequent accumulation of a red metabolic precursor in ade host cells. Applications of YACs Applications of YACs range from generating whole DNA libraries of the genomes of higher organisms to identifying essential mammalian chromosomal sequences necessary for the future construction of specialized mammalian artificial chromosomes (MACs). Helps in the study of regulation of gene expression by cis-acting, controlling DNA elements, that are present either upstream or downstream of large eukaryotic genes, after the transfer of these YACs from yeast to mammalian cells. YAC libraries has greatly advanced the analysis of genomes previously cloned in cosmid vectors. For example, YAC clones have been used as hybridization probes for the screening of cDNA libraries, thus simplifying the characterization of unidentified genes. Recent technological developments allow the transfer of YACs into mouse embryonal stem (ES) cells and the subsequent generation of transgenic mice. 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