Biology

The article  Swarms of Asian Ladybug Question  discusses the unnatural occurrence of Asian ladybugs in America, greatly affecting both the citizens and its native counterparts. The article answers the frequently asked questions about the Asian ladybugs themselves, their reproduction, diet, lifestyle, and how they affect the local ecosystem.

    Apparently, the Asian ladybugs identifiable with a black M-shape on the plate atop their heads originated from the eastern regions of Asia which include Siberia. Through imports of exotic flora, the Asian ladybugs managed to sneak into the country. They propagated quickly and expanded their territory all over the United States, devouring aphids and other insects including native ladybugs. The reason behind their invasion of homes across America is the fact that they need a warm place to stay and hibernate during winter unlike their counterparts that find natural warm spots to hibernate in. These Asian ladybugs also tend to send out messages to their kind whenever they find a good place to stay in, which would explain the swarms of these pests inside homes. Asian ladybugs also excrete a stinky fluid that can discourage larger predators from attacking them. However, when they get squished along produce such as grapes, their unpleasant fluids affect their taste. Furthermore, these Asian ladybugs are more aggressive than their native counterparts, which explains why they tend to bite humans once they land on their skin.

    In my opinion, the Asian ladybugs disrupted the natural ecosystem as well as the lives of people in the United States, as they became more of a pest than a help to the natural ecosystem and humans. Before they invaded the United States, the native ladybugs controlled aphid growth and were less bothersome to humans. Initially when these Asian bugs arrived, they were more of a benefit especially to farmers since they kill off aphids in crops. However, they propagated quickly and the imbalance occurred. Once there were lesser aphids in crops, they hunted the food source of their native counterparts and preyed on them as well. They also tend to invade the homes of people and other wildlife where they are unwelcome since they can become a bother. Therefore, they are most likely labeled as pests to the natural ecosystem as well as to human settlements.

The fruit fly, Drosophila melangaster, was used as an instrument to study the inheritance and transmission of some characters. The characters used were eye color (red or white) and antenna mutation. Monohybrid crossings revealed phenotypic ratios of 3 1, supporting the experiments hypothesis.

Introduction
In the early twentieth century, the tiny fruitfly, Drosophila melanogaster, became the wonder geneticists tool. It was made famous by Thomas Morgan, an American geneticist in 1912, who used it extensively in his researches to verify the assertions of Gregor Mendel, and also to locate the position of genes on chromosomes (chromosome mapping).

Drosophila melanogaster, the fruit fly is a very suitable instrument for genetic studies. One of the advantages is that it is tiny, the adult is only 0.5cm long, and so can be kept in the laboratory in large numbers. Drosophila are small flies, typically pale yellow to reddish brown to black, with red eyes (Drosophila, 2009). The males can easily be distinguished from the females because the males have rounded abdomens while the females have pointed abdomens. Also, it completes its life cycle within two weeks and breeds in large numbers, enabling geneticists to follow the transmission of characters through several generations in a short period. It has only homologous pairs of fairly large chromosomes in its somatic cells and it has many easily distinguishable discontinuous characteristics.

Drosophila has been found to have four pairs of chromosomes  a pair of sex chromosomes (X or Y) and three pairs of autosomes (2, 3 and 4). The size of the genome is about 165 million bases and contains an estimated 14,000 genes (by comparison, the human genome has 3,300 million bases and may have about 70,000 genes yeast has about 5800 genes in 13.5 million bases) (Introduction to Drosophila melanogaster, 2006). The analysis of the entire genome of the fruit fly has almost been completed.
The aim of this experiment is to verify the hypothesis which states that if there were 10 wild males and 10 mutated females in the F1 generation, there would be a phenotypical ratio of 3 mutated flies to 1 normal fly.

Methods
The materials used during this experiment were adsorbent wand, petri dish, several Drosophila vials and labels, FlyNap solution, fly morgue.
The whole experiment was conducted over the space of three weeks. The procedures will be divided according to the weeks.
Week 1
The first part of the experiment was to anesthetize the flies. This was done using a FlyNap. A wand was prepared and dipped inside the FlyNap solution. The wand was then introduced into the container containing the selected flies and held there for about two minutes. The anesthetized flies were shaken out on a white card. With a dissecting microscope, the adults were observed and their genders and physical characteristics were noted. The adults were separated according to their genders with the use of the properties differentiating the males from the females.
Week 2
The adults were allowed to mate the previous week and the offsprings observed the following week. The fly vials were retrieved and the eggs and larvae checked for. All the flies present were anesthetized using the FlyNap solution. The P generations of flies were removed and the eggs and larvae left in the vial. These were then allowed to incubate in the incubator, pending their observation the following week.
Week 3
A fresh vial of food was prepared for the new generation of flies. Yeast was also added to the food. The flies were labeled with the corresponding mutant letter. Again, the flies were anesthetized using FlyNap. Their characteristics were observed and recorded. The flies were sorted according to their phenotypic characteristics. Of these, 10 males and 10 females were selected and put in the new fresh vials and allowed to mate and produce the F2 generation of offsprings. After some days, the F2 offsprings were observed and their phenotypes recorded (Carolina Drosophila Manual, 2009).

Results
 SHAPE   MERGEFORMAT
Figure 1. A monohybrid cross between a wild type male and a mutated female.
 SHAPE   MERGEFORMAT
Figure 2. A second monohybrid cross between a mutated male (antenna) and a White eyed female.
Mutation A represents antenna formation, mutation B represents tan body and white eye, while mutation C represents wingless flies.
After the WB X A monohybrid cross, it was discovered that all the F1 generation of offsprings looked alike, that is all the phenotypes were of the wild type.
Observed  of flies 21 males and 12 females.
During a second cross between AB and B flies, all the offsprings expressed the same mutated antennae trait. 20 offsprings had red eyes and 11 others had white eyes.
Observed  of flies 8 males and 23 females.

BXbAXbaYAYaXBA Red eyes
XBXbAA
Mutated antenna Red eyes
XBXbAa
Mutated antennaB Red eyes
XBYAA
Mutated antennaB Red eyes
XBYAa
Mutated antennaXBa Red eyes
XBXbAa
Mutated antenna Red eyes
XBXbaa
Normal antennaB Red eyes
XBYAa
Mutated antennaB Red eyes
XBYaa
Normal antennaXbA White eyes
XbXbAA
Mutated antenna White eyes
XbXbAa
Mutated antennaB White eyes
XbYAA
Mutated antennaB White eyes
XbYAa
Mutated antennaXba White eyes
XbXbAa
Mutated antenna White eyes
XbXbaa
Normal antennaB White eyes
XbYAa
Mutated antennaB White eyes
XbYaa
Normal antennaFigure 3. Punnett square with a dihybrid cross showing inheritance patterns through the first and second filial generations of two characters.

Discussion
The monohybrid cross illustrated in Fig. 2 supports the hypothesis. The females which expressed the same phenotype as the parents were all mutant, that is, they had antenna mutation. During the course of the experiment, the cross between WB and A did not work. This was probably due to excess light. All the offsprings had the wild type phenotype. The correct phenotypic ratio should have been ratio 31 of red to white. This would have confirmed that the red eye trait is dominant to the white eye trait. Analysis of why this did not work is beyond the scope of this experiment.

A second cross between AB and B gave a different result. The observed phenotypes were 15 red eyed females with mutated antenna, 8 white eyed females with mutated antenna, 5 red eyed males with mutated antenna and 3 white eyed males with mutated antenna. This would give a phenotypic ratio of 20 red eyed offsprings to 11 white eyed offsprings, although, all had mutated antennae. The observed F1 phenotypes did not match with the expected F1 phenotypes. This is probably due to some errors during the experiment.
Figure 3 shows the results of the dihybrid cross to study the inheritance patterns of the two characters, that is, eye color and antenna mutation. Each member of the F1 generation undergoes meiosis to produce six kinds of gametes, XBA, XBa, XbA, Xba, YA and Ya. It can be seen that the alleles for the two characters were independently assorted. If members of the F1 generation were then allowed to cross among themselves, the F2 generation so produced shows 4 phenotypes and 12 genotypes. The four phenotypes which appear in the ratio 6 2 6 2 are as follows
six red eyed with mutated antenna
two red eyed with normal antenna
six white eyed with mutated antenna
two white eyed with normal antenna
Observing the Punnett square closely, it is noticed that the phenotypic ratio of red eyes to white eyes for each sex was 1 1, that is, the male flies had a 1 1 ratio for red eyes versus white eyes and the female flies, 1 1 ratio for red eyes versus white eyes. Again, the ratio of mutated antenna to normal antenna was 3 1 for all the red eyed males. Same thing can be noticed for all the red eyed females, white eyed males, and white eyed females.

Human Immunodeficiency Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS) are two complex diseases that are causing very serious health problems to humans. HIV was first discovered in 1985 and was eventually assumed by scientists that it was the virus that caused AIDS (Cichocki, 2009b). Although HIV and AIDS epidemics are two different diseases, they have been equally creating significant health concerns to humans all over the world throughout the years. The most common means documented in the spread of the HIV virus is through sexual contact, although recent cases reveal that sharing of needles when abusing intravenous drugs has been steadily contributing a considerable percentage of the entire HIV transmission. Because of the enormous health concerns brought by HIV and AIDS and the puzzling origins, connection, and treatment of the two illnesses, this paper will comprehensively examine the link between HIV and AIDS, the beginnings and new discoveries concerning the diseases, the current state of the problem, and the direction of works focused on HIV and AIDS.

Transformation of HIV to AIDS
    HIV is a virus that is transmissible from person to person by means of swapping of body fluids such as vaginal secretions, breast milk, semen, and blood (Cichocki, 2009a). The HIV virus is transmitted through body fluids during breastfeeding, childbirth, sharing of needles, blood transfusion, and sexual contact. A person infected with HIV does not automatically mean that he or she also has AIDS. In essence, once the HIV virus is within the body, it strategically attacks the CD4 cells, which are the detailed immune system cells of the human body (Cichocki, 2009a). The virus attaches to and infects the CD4 cells by infusing HIV proteins into the cells. In due course, each of the CD4 cell is slowly damaged as the HIV virus propagates and attacks them. As this series goes on, the immune system of the infected body deteriorates, and the person becomes so vulnerable to a number of various infections which can make the person severely sick and even lead to his or her death.

    Basically, in every cubic millimeter of blood, humans have between 600 and 1,500 CD4 cells (Noble, 2009). People who develop AIDS have very much lower levels of such cells, generally under 200 cells per cubic millimeter of blood or below 14 percent of all the lymphocytes (Noble, 2009). These low levels of immune cells clarify why AIDS-affected people are very susceptible to different diseases. The diseases that can distress people with AIDS are usually swollen glands and mild flu-like illness however, such may also include either one of the 28 specific diseases in the case of children victims, and one of the 26 identified diseases in the case of adult victims (Noble, 2009).

Developments in the Field from the Earliest Beginnings
    From the time HIV and AIDS diseases infected the humans in the 1980s many scientists have been mystified of their origins. As a result, these diseases have continually generated countless arguments and fierce debates. Many experts have, however, all agreed and confirmed that HIV is a type of lentivirus. Numerous investigations regarding the beginnings of HIV have revealed that HIV is a descendant of a Simian Immunodeficiency Virus, which is a type of lentivirus that affects monkeys (Kanabus, Allen,  de Boer, 2009). The closest HIV counterpart, which is the SIVcpz found in chimpanzees, was first discovered in 1999. Scientists found that there are two different Simian Immunodeficiency Viruses that are capable of developing a third type of virus for the chimpanzees of Western Africa. Unfortunately, this third strain of virus was not only found to be contagious to other chimpanzees, but more alarmingly, it was also discovered to be contagious to humans. Because of the discovery of this vital evidence, many experts believe that the first transfer of HIV to humans occurred in the continent of Africa (Kanabus, Allen,  de Boer, 2009).

    Several factors may have played a role in the unexpected transmission of HIV virus from Africa to the rest of the world, most of which took place in the last part of the 20th century. International and national travels, for instance, may be considered to have significantly contributed in the initial spread of HIV. Likewise, during the period, demand for blood transfusion has significantly increased. Unfortunately, some of the unscreened bloods may have been infected with HIV virus and may have surreptitiously infected the people who received the blood. Moreover, during the 1970s, availability of heroin helped trigger a growth in intravenous drug use, which provided another medium for the virus to spread. 

    The first licensed therapeutic drug for HIV was AZT, or zidovudine, which became very popular in 1987. Numerous researches discovered that AZT increased CD4 cell counts, reduced opportunistic infections, and increased survival rate among AIDS infected patients (Noble, 2009). However, subsequent studies, particularly the Concorde Study, have revealed that patients who have taken the drug received no or little lasting benefit (Noble, 2009). As a result, in the succeeding years, other types of anti-HIV drugs have been developed, such as protease inhibitors, which were specifically designed to attack HIV proteins. Recent studies also found that when these different medications are reciprocally taken, they bring more positive results to the patients as compared to AZT treatment alone.

The Current State of Affairs
    In June 2007, the UNAIDS published the world statistics of the HIV epidemic. The statistics reveal that in 2006, more than 39 million people are infected with HIV, over 2.9 million died of AIDS, and approximately 5 million people in middle and low income countries do not have access to HIV medications (Cichocki, 2007). As of 2008, the statistics somewhat declined but still remained in a very alarming number. The estimates claim that 33.4 million people are still living with HIV, and AIDS deaths totaled to roughly 2 million (AVERT, 2009). Unfortunately, as of the moment, there is no recognized comprehensive treatment for HIV infection. Although many people are no longer dying from AIDS given that there are already available medications that decelerate the HIV virus ability to reproduce, the fact remains that these infected people are still not free from the deadly transmissible virus (Cichocki, 2009a).

    At present, various domestic and international organizations, such as AVERT and the Food and Drug Administration, are focusing on reviewing and monitoring areas related to medical devices, biologics, and drugs for the prevention of HIV- and AIDS-related conditions. Several areas are continually taken by these organizations that influence prevention of the HIV transmission, including the following (1) making sure that the blood supply is safe from the virus and other infectious disease (2) monitoring the quality of barrier products such as medical and surgical gloves, dental dams, condoms, etc. (3) working with government and industry developers of both therapeutic and preventive vaccines for HIV such as Core ProteinsPesticides, DNA Plasmid, Envelope ProteinsPeptides, Retroviral Vectors, Inactivated HIV-1, Nucleic Acid-based vaccines, and Recombinant Live Vectors and (4) working with other researchers and sponsors to build up realistic, appropriate microbicide to avert the transmission of HIV (U.S. Department of Health  Human Services HHS, 2009). 

Direction of Work in the Future and Potential Positive and Negative Impacts
    At present, there is no known treatment for HIV and AIDS, as well as a validated case of a person cured of HIV infection. Estimates reveal that in the next two decades, roughly 70 million people may die from AIDS (Norris, 2008). The main reason for the future increase of infection is that many of the infected people may deem that they are not infected with the virus. Unfortunately, the current drugs available that suppress the negative effects of HIV may likewise be considered an impediment to the efforts of restraining future epidemic. The reason for this distress is that people with HIV and AIDS are now living with the viral hazards for such a long time as the accomplishment of treatments in reducing percentage of death preserves the good health of the infected people (Norris, 2008). As a result of these medications, patients may likewise increase their chances of transmitting the disease to other people.

    As of the moment, future preventive strategies will continually focus on the use of condoms to reduce the transmission of the HIV virus. In addition, researchers are also aspiring to perfectly develop a microbicidal creams or gels for females, to be utilized in a way that is comparable to spermicides. With regard to future vaccines, the research is only expected to focus on preventive HIV vaccines. For years, researchers have been more successful in working out preventive vaccines than they have been in expounding therapeutic vaccines. However, many experts are still very optimistic that in the future, the development of a precautionary treatment may make the danger of HIV as isolated as the danger posed by small pox or polio.

Conclusion
    The spread of HIV to humans became known during the early 1980s. Scientists eventually concluded that HIV is the virus that causes the development of AIDS to human beings. However, a person infected with HIV does not automatically mean that he or she also has the AIDS. Some people with HIV infection live for many years without developing the AIDS disease. Unfortunately, available medications today are still not capable of entirely eradicating HIV virus from the body, leaving the infected person capable to infect other people. Many experts, nevertheless, believe that in the future, new developments regarding the treatment of HIV and AIDS will be discovered. As of the present time, however, the possibility of living a longer, healthier life, free from HIV and AIDS, only increases when one understands the nature of these conditions.

Infectious diseases are a group of conditions that are caused by harmful microorganisms such as bacteria, fungi, viruses, parasites, etc, and may spread from one person to another either directly or indirectly (WHO 2009).  Every year infectious diseases kill million of people throughout the world and are one of the single largest causes of mortality and health concerns.  Infectious diseases may spread through contact, vectors, inhaling droplets containing the microorganisms, consuming food or water contaminated with the microorganisms, through sex with an infected person (body fluids), etc.  A pregnant woman can also transmit an infectious disease to the unborn child (Mayo 2009).   
    Infectious diseases have been throughout history causing havoc in man. The ancient Egyptian and the Greek civilizations have had their sorrows with epidemics of leprosy, tuberculosis and diphtheria.  Epidemics affected populations seriously including trade, politics, social life, etc.  Epidemics of small pox and plagues followed soon affected the Roman Empire hugely.  In the period between 1104 and 1110 BC, about 90  of the European population was wiped off with plague.  In the 15th and 16th centuries following the discovery of the New World, even the Americas was ravaged with plague, with about 25  of the populations of the Aztecs being wiped out in 1520 alone.  Syphilis became rampant in Europe since the late portion of the 15th century.  There was also lot of problems with leprosy in Europe during the Middle Ages, as lepers were heavily discriminated and had to carry a bell to warn others (Nelson and Williams 2006).

    During the middle Ages efforts were made to identify the cause of infectious diseases and develop a method to identify, treat and prevent them.  In the 1630s, the Cinchona bark was utilized to treat malaria in Europe.  Edward Jenner began inoculating people against the small pox virus by using the cow pox fluid lesions.  In the Western world, cholera, malaria, yellow fever, plague, etc, were huge concerns during the later portion of the 19th century.  Several antimalarial drugs were discovered during the 1930s, and in the 1940s, Alexander Fleming discovered penicillin that could be used against several pathological bacteria.  Now man had control over several bacterial diseases.  Vaccines began to be developed for several diseases since the start of the 20th century.  Besides, in the US efforts were made to improve sanitation, water hygiene, provide vaccines and healthcare facilities, improved means of diagnosis, etc, which helped to reduce the morbidity and mortality from infectious diseases.  There was also an increase in the lifespan of people throughout the US (Nelson and Williams 2006).

    H1N1 flu or formerly known as Swine flu had caused pandemics throughout the world in the year 2008 and 2009.  However, todays advances in medicine have ensured that the disease remains in control.  Antiviral drugs such as oseltamivir and zanamivir are useful in treating the disease in high-risk groups.  Today the antiviral drugs are even used as a prophylaxis measure in the high risk groups.  Today vaccination against swine flu has been developed in the form of injections and nasal sprays that can help to protect millions across the world (CDC 2010).

    Some of the most common infectious diseases across the world include sleeping sickness, cholera, dengue, hepatitis A, B  C, influenza, Japanese encephalitis, malaria, measles, meningitis, shigellosis, tuberculosis, HIVAIDS, typhoid, yellow fever, etc.  Some of the common emerging infectious include anthrax, E. coli infection, prion diseases, small pox, drug resistant tuberculosis, Lymes disease, SARS, botulism, etc.  Some of these infections are actually old infectious that are reappearing today and are causing havoc in the public health network.  The US government and federal agencies have developed a new strategy to manage these conditions.  They are researching the relationship between the pathogen and its environment and further developing diagnostic tests, drugs, vaccines and other preventive methods of overcoming these infections.  Around the globe an international network is being developed to ensure that any disease concern in one are can be addressed in order to prevent a pandemic (NIAID 2009).

    Ever since the identification of the human DNA by Watson and Crick in 1953, there has been tremendous interest in studying the genetic code further and identifying places at which the human susceptibility to diseases would be determined.  The Human Genome Project undertaken in 1990s tried to identify all the human genes and was able to recognize about 10 million locations of single-base DNA differences.  These differences occurred between one individual and another and there is increasing speculation whether this could determine human susceptibility or resistance to an infecting organism.  Furtherer scientists are also trying to use gene therapy and specialized medications that would act at the genetic level.  In this way infectious diseases can be better managed.  Scientists have also found a promising vaccine for HIV after struggling for its development for more than 25 years (Nelson and Williams 2006). 

Mutation can be a result of damage in the genetic material through exposure to mutagens such as chemical agents, or physical agents some examples are ultraviolet rays, transposons, and ethidium bromide. (Campbell, 2005)  Mutant plant cells accumulating amino acids are plant cells containing variant DNA compared to all the other normal cells.

    Since the identity of the amino acids being produced is unknown, as well as the quantity of these amino acids produced by normal and mutated cells, the first step to take is the quantification and identification of amino acids in tissue culture. Immunofluorescence is an efficient method of detection of amino acids for tissue cultured cells. Through amino acid recognition segregation of functional cell types is possible, consequently, identifying the mutant cells. (Signature Immunologics, 2000) Immunofluorescence is the process by which fluorescent dyes are used for labeling antibodies to demonstrate the antibodys presence in a tissue culture.

    In performing this, with Sherry Laboratory as a source, modified 30 mm polystyrene dishes are used. One shall drill out a circle on the bottom of the dish and attach a glass coverslip onto the drilled hole. A PBS formulation as vehicle shall be used for cultured cells due to its characteristic lack of embedding matrix. Liquid exchanges should not remove the primary cell specimen through the process of fixation to coverslipping. Mild fluid transfer is adequate for washes. The well created earlier should not dry out and must continuously be filled. Triton X-100 (0.1) is added to the primary antiserum diluent to improve antibody penetration. Culture dishes should be labeled with fluorophores and coverslipped in an anti-fade mountant. The dishes shall, then, be stored under optimal conditions for fluorophores (FITC 0C, TRITC 4C) (Signature Immunologics, 2000) Stored samples can, then, be viewed for observation through immunofluorescence microscopy.

     After  the selection of mutant plant cells accumulating amino acids, one is now able to use it for the production of secondary products in cell cultures and for crop improvement in the subsequent ways. In the production of secondary metabolites, scientists usually use plants as the major source of ingredients.  These secondary metabolites are used in suspension cultures which serve as cell constituents which are not essential for specimens subjected to it. These secondary metabolites include alkaloids, glycosides, terpenoids and a variety of flavours and more. The manufacture of these products can be increased with human intervention. However, through mutations, such as those mutants accumulating amino acids levels higher, there is a probability that the production of secondary metabolites be increased. (Students Guide.In)

    The inability of humans and animals to synthesize particular amino acids has been a subject of interest for a long time and researchers have focused on using crop plants to provide these essential amino acids for human and animal consumption. It was found that crop plants have naturally occurring amino acids in them. Among these amino acids are lysine, tryptophan and methionine. With mutants accumulating amino acids at hand, the production of amino acid-enriched crops will be much easier. Through genetic engineering, the isolated mutants can be transferred to crops not demonstrating high levels of amino acid production (Galili, 2008)

 If the production of crops with high levels of essential amino acids is made possible, then it would greatly help mankind. With this development, people and animals will be consuming more nutritional foods. In addition, economic growth may also be achieved through this genetic breakthrough.

Answers
I. Describe a strategy for selection of mutant plant cells accumulating amino acids
    -     Immunofluorescence is an efficient method of detection of amino acids for tissue cultured cells. Through amino acid recognition segregation of functional cell types is possible, consequently, identifying the mutant cells.

II. Explain the potential use of such mutants
for the production of secondary products in cell cultures
-    Through mutations, such as those mutants accumulating amino acids levels higher, there is a probability that the production of secondary metabolites be increased.
    b. for crop improvement
-    With mutants accumulating amino acids at hand, the production of amino acid-enriched crops will be much easier. Through genetic engineering, the isolated mutants can be transferred to crops not demonstrating high levels of amino acid production.

Classical breeding systems have gained some success when it comes to the development of herbicide resistant cultivars which includes triazine tolerant canola varieties and metribuzin tolerant soybean. This type of breeding has primarily relied on intraspecific genetic variation from recombinationsegregationsexual hybridization and to a lesser degree, mutation-induced variability (Fowler  1992).

Herbicides that portray low toxicity to crop species take on an important part in terms of weed control in modern agriculture (Duke 1996). But these selective herbicides are more often than not only available for the major crops because the development of such yields for high costs.

Significant losses in the fields are caused by excessive weed growth which in turn forces several crops into competing for nutrients and sunlight. Since herbicides are not capable of differentiating plants that are classified as weeds and plants that are crops, in turn, conventional agricultural systems are only able to make use of selective herbicides. These herbicides are not known to of making any harm to the crops but are not very effective when it comes to the removal of all weed types.

Many crops have been genetically altered to be resistant when it comes to non-selective herbicides. These so called transgenic crops have genes that allow them to decompose or degrade the active ingredient found in a herbicide, making it not detrimental or undamaging. Hence farmers are able to control weeds without difficulty in time of the growing season and have more flexibility when choosing the appropriate times for spraying.

These herbicide resistant crops facilitate low or even no tillage cultural systems, which a lot of farmers regard to be further sustainable. An additional advantage of this is that it allows farmers to manage weeds without having to turn to some of the more environmentally supposed kinds of herbicides. Critics argue that for some cases the use of these herbicide resistant crops may lead to an increase of herbicide use hence promote the development and use of herbicide resistant weeds thus create damage to the biodiversity on the farm.
Studies and field trials that were conducted on these herbicide resistant crops have revealed that different herbicides as well as herbicide application practices have an effect on the amount of wild plants that can be found on the fields or farms.

Rising technologies include vitro mutagenesis andor selection, embryo rescue, parasexual hybridizations, and finally genetic transformations. Genetic transformation of plants to be herbicide resistance is one method of achieving these selective herbicides. In genetic transformation it is necessary that there is the ability to transform the crop or specie of interest plus the gene which confers herbicide resistance should be available. Same goes for vitro mutagenesis where production of the herbicide resistance crops will be possible through the reintroduction of the DNA into the species of interest (Duke 1996).

Herbicide resistance trait is now transferrable to a crop and hence a new strategy for strigaweed control has been demonstrated. Prior to planting the crop, its seeds are soak in a herbicide. These seeds become poisonous to the weed or striga parasite but the seeds are unharmed. These seeds grow and sprout with no obstruction or holdup. When the crop is harvested, the herbicide then becomes decomposed and disappears.

These technologies are said to have impact the development of herbicide resistant crops. The technologies will not dodge the classical breeding method due to inherent deficiencies, but these technologies should provide desirable sources of genetic or inherited herbicide tolerance that can be refined, multiplied, recombined, and distributed by means of classical variety development knowledge and technologies (Slater 2003).

Crop improvement is been the main strategy for a farmer. Rediscovery of Mendels laws of Heredity at the very beginning of the last century and the subsequent intensive researches have clarified many good details about the very structure and function of DNA as the basis for all demonstrated characters and functions of plants and all organisms.  New methods have been developed and used commercially for genetic improvements and modifications of crops in agriculture and simpler and sure faster molecular methods of health care approaches and production of medicinally important molecules medicine. One basic idea is that the sub-cellular genetic factors (discreet DNA sequences) constitute the structure and functions of all the organisms. Discovery of exhaustive DNA related information prompt attempts to find useful genes and introduce into the desired host plants. Well worked techniques are now available and are proving as valuable. Till recently it was found necessary to insert foreign useful DNA into organisms suffering from lack such characters and after the 1980s several methods have been developed and are still being developed for DNA introduction into a host crop plant.

Methods for Delivery of Foreign DNA
In most situations transformations have been carried on of full plants under aseptic conditions at the cellular sub-cellular levels. After this the cells or the tissues transformed are promoted by suitable growth media for the formation of full plantlets which are then taken out to the natural conditions and tested in detail before entering them into plant breeding programs. The other feature is that a marker genes, such as genes for antibiotic resistances, are integrated with the gene sequence to be introduced.

Agrobacterium mediated transformation  Understanding the mechanism of crown gall (tumor) formation particularly in many dicotyledonous plants was the origin of this technology. Agrobacterium tumefaciens bacterium has the natural capability of introducing its DNA (T-DNA) into the infected cells where the integrated DNA piece produces two basic plant growth hormones  auxins and cytokinins, both of which promote cell division which do not dor any normal structures such as shoots. A related species A. rhizogenes has the capability of promoting numerous root growths. This mechanism has been used in several plant species after the genes for tumor growth have removed by molecular methods to form a disarmed vector.
Biolistic- A tissue or cells to be transformation are exposed to high velocity bullets coated the foreign DNA.

This is an often used method
Electroporation  As in biolosistics but the movement of the DNA is also forced or promoted by an electric charge.

Calcium Chloride methods. The cells to be transformed are sensitized such as with different extreme temperature regimes.  Such cells are exposed for brief times to a calcium chloride solution which facilitates channels in the cell membranes for DNA entry.

Other methods  There are many other methods which have been developed but not used often. They are silicon carbide based, micro-injection, polymers, and others.

A Successful Vector  A good vector has to carry DNA safely till the DNA is released into appropriate site.

The DNA has to be stably integrated into the host cells. The DNA should be functional and express effectively in the host cell without disturbing the original genetic function of the host DNA. 

Agrobacterium has the advantage that it can also be used in normal conditions without the need for aseptic conditions. This bacterium is versatile in the sense it can transfect any and all the kinds of cells and tissues.

There have been many reports which demonstrate that even seedlings grown in non-aseptic conditions can also can be transfected.