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The human manipulation of the transfer of genetic information between organisms has been ongoing for that past 10,000 years. The cultivation of grains and domestication of animals were our first experiences with this manipulation. With science constantly advancing, there has been a massive improvement in what methods we use to make it easier to get the most wanted kinds of livestock and plants. In this report there will be discussion about selective breeding and transgenesis and the biological implications both of these processes have.
They are very common examples of genetic manipulation.
Transgenesis is defined as a process in which a desired gene is introduced from one organism into the genome of another organism. The intention of transgenesis is that the resulting transgenic organism will show the desired gene and show some property or characteristic. This process is able to take place because the genetic code is universal for all living things.
Selective breeding is defined as a process where humans search for organisms that have the desired phenotypic traits.
Breeders then select two parents that may have beneficial phenotypic traits to reproduce, yielding offspring with that specific trait.
An example of a transgenic animal is a transgenic cow. The transgenic cow has an additional gene (called a transgene) in each cell. The transgene protein can only be located and removed from the cows milk, because the transgene is only found in the mammary tissue.
AgResearch New Zealand has successfully been producing transgenic cows that make genetically modified milk, they also produce therapeutic proteins that can treat human diseases or conditions.
Scientists search for the traits that are desired in a transgenic animal. Once decided what kind of livestock is required, it is a matter of finding the transgene and aligning it logically.
Removing the transgene from an organism’s DNA was one of the first methods Scientists used. Scientists have recently found that if the gene sequence is known, they can synthesis the gene of interest in the lab.
Once the gene has been identified and located in the DNA, scientists remove the gene sequence. Restriction enzymes are used to cut a specific section of the DNA leaving several pieces of varying lengths. A length will be the desired gene. It will have sticky ends, which helps it glue back into a vector. Restriction enzymes come from bacteria and their purpose is to act as a defence mechanism. When viruses attack, bacteria kill them but cutting up both strands of DNA, at a specific sequence.
After the gene is isolated, the transgene is created by modifying parts of the gene. A gene construct contains all the needed information for the process of transfection. This includes a tissue specific promoter sequence, this establishes the beginning of a gene sequence. The gene construct includes the gene of interest, this is the desired gene. It has a terminator sequence, this is to indicate the end of the information for making that protein. A gene construct also has an antibiotic resistance gene. This is added to only choose cells that have effectively taken up the gene construct.
The gene construct is incorporated into the genome of a bovine (cow) cell using a process called transformation.Transformation involves the delivery of a transgene transporting it into the nucleus of a recipient cell and integrating into a chromosome so it will be inherited in the next generation.
Selecting for transgene positive cells
To confirm that the desired gene has been incorporated, all of the cells must be screened; to make sure that the gene will have the antibiotic gene. Antibiotics are applied to the cells by scientists, if the cells do not have the antibiotic gene they will die. The cells with the incorporated trangene will survive, they will eventually divide and create their own colony of identical cells. The researchers characterise their clones further by using an enzymatic reaction called Polymerase Chain Reaction. This method is used to check that the transgene is there. Sometimes there can be a cell growing without the transgene, this is called a false positive.
Make transgenic embryo using nuclear transfer
Eggs are sourced from the abattoir, and the DNA is removed from the egg. The egg and the transgenic cell are fused together, the DNA that belonged to the transgenic cell now belongs to the egg. It is stimulated so the egg grows, it remains in a lab for a week. The egg is then transferred into a recipient cow. The gestation is monitored by researchers for nine months, and hopefully at the end of this process a healthy calf is produced.
The first step I will be explaining is step four, designing and constructing the gene. I will be explaining Polymerase Chain Reaction. A ligation enzyme is used to help everything bond back together. The Polymerase Chain Reaction is repeatedly heating and cooling a target sequence of DNA and copying the sequence creating millions of identical sequences. For half an hour the product is incubated at 16 degrees in a water bath. This is a technique used to copy and multiply a piece of DNA millions of times. The DNA is heated to 98 degrees celsius, the DNA denatures, this separates the single strands and exposes the base sequences. The DNA is cooled down to 65 degrees celsius, the DNA primers anneal using the base complementary rule on the target DNA. Taq polymerase is an enzyme that can be heated up to maximum temperatures. The enzyme taq polymerase binds to the sequences and connects the nucleotides. This cycle is repeated until there millions of identical sequences.
The second step I will be explain is step three, gene isolation. I will be explaining Restriction Enzymes. Restriction enzymes are used to cut a specific section of the DNA leaving several pieces of varying lengths. A sequence length will have the desired gene. It will have sticky ends, which helps it glue back into a vector. Restriction enzymes come from bacteria and their purpose is to act as a defence mechanism. When viruses attack, bacteria kill them but cutting up both strands of DNA, at a specific sequence.
The selected phenotypic trait (what we see physically expressed on the outside), is chosen to be selectively breed.
Parents can be chosen by observation of the desired physical characteristics or there can be a combination of selective breeding and biotechnology to determine who the parents should be. An example of a process that could be used is genome analysis. This process increases the reliability of producing the offspring who hold the desired characteristics.
Once the offspring have developed enough to observe their physical characteristics, the offspring that displays the characteristics closest to the desired ones are selected. The remaining offspring that aren’t chosen are usually culled (removing animals that are unwanted from a breeding group depending on specific criteria).
Breeders frequently end up breeding animals incestually to produce consistent offspring who have practically the same desired characteristics. The inbreeding can consequently create problems for the organisms. Inbreeding depression is one example of the problems of incestual breeding. Populations are also more susceptible to environment pressure.
Repeat this process until the desired characteristics are expressed
The first step I will be expanding is step 2 during the selection process. Gel electrophoresis is a process that is used to compare genomes of different organisms or individuals. It can also be used to locate and identify a gene in an individual’s genome. The steps for this process are as follows:
The restriction enzyme cuts DNA into fragments
The DNA fragments are poured into the wells in the gel
An electric voltage is applied to the gel. This moves the fragments across the gel. (The DNA is negatively charged and so it will be attracted to the opposite end of the gel, therefore it will travel towards the other side.)
The smaller the DNA fragment is, the faster and farther it will travel through the gel.
The DNA fragments will spread out and make a pattern of bands on the gel.
These patterns can then be compared to other samples of DNA or the pattern of the desired gene to confirm the cross will be with another desired gene.
Gel Electrophoresis is useful because if researchers know the sequence of an organism’s DNA they can use this information to study specific genes. They can also use this information to compare the genes with other organisms and to discover the functions of different genes and gene combinations.
The second step I will be expanding is step four during the breeding process. I will be explaining Embryo transfer. This technique is when embryos that are produced by IVF are transferred into the uterus of an unrelated female (called a surrogate). The embryo that is developing inside of the surrogate are genetically unrelated to each other. Embryo transfer is a technique that is used to help females who have reproductive problems produce offspring. Female animals tend to only release a few eggs each cycle (human females usually only release one). Drugs can stimulate the release of a greater number of eggs (multiple ovulation). This is combined with embryo transfer (this technique is called multiple ovulation embryo transfer) enabling a single female to produce a large number of offspring.
Genetically engineered animals could hold great potential in fields such as agriculture, medicine and industry. The effect of transgenic animals reaches ecosystems, survival of the population, evolution, health and welfare of the organism, and genetic biodiversity.
The advances of transgenic technology is improving livestock and animal wellbeing. For example the advances in the technology have improved resistance to disease. The development of molecular biology has made it easier to develop traits in animals more quickly, thereby developing and growing the herds with desired characteristics can be a much faster process. Gene modification has made things like milk or meat from cows more valuable. For example, milk with more casein requires less processing to make into cheese and additionally has higher calcium levels. Ag Research showed that their first transgenic cows had extra bovine kappa casein genes that were purposely placed in their genome.
This evidence showed that transgenic technology had the potential to benefit animal health, the milk could, not only be modified specifically to benefit the cow, it could also be modified to improve growth and survival of calves; intercept animal diseases such as mastitis; make milk with human health advantages; and help milk processing into dairy products. Currently overseas milk and meat substances from transgenic animals are not allowed to be added to New Zealand products for animal or human consumption. The process of transgenesis has shown an effect over ecosystems. For Ag Research to experiment with transgenic cows, they were required to follow strict guidelines for the care and containment of the cows. Transgenic cows are classified as new organisms and regulated by the Hazardous Substances and New Organisms (HSNO) Act. This is overseen by the Environmental Protection Agency (EPA). The EPA holds the rules for introducing any hazardous substances or new organisms to New Zealand. Before Ag Research began, they had to send an application to the EPA. EPA assesses the risks and benefits of the intended research and makes a decision on whether the work can be done. Transgenesis has also shown an effect on the environment.
Ag Research kept the transgenic cows in confinement at Ruakura facility with restricted access and environmental monitoring. The transgenic animals cannot leave the facility and the farmers must follow strict rules when disposing of waste. The Ministry of Agriculture and Forestry New Zealand monitor this animal containment facility. All the waste materials from the facility must be disposed of onsite. The milk is treated by fermentation, diluted and then sprayed across the field. The ethics around the process of transgenesis is a key part of biotechnology. Animals that have transgenic genes are very different to the genes animals would have if they went through natural genetic selection. Transgenic animals in New Zealand are held in containment, and the technologies are highly monitored. However, issues are raised in animal welfare when an animals genetics are modified. These issues that are raised are looked at differently according to individuals personal beliefs and values. The ethical concerns that are brought to attention continue to be addressed as the technology grows. The ongoing transgenic research will be dependant on what ethical and societal discussions are raised. The risks and benefits of making transgenic cows will be looked at and there will be a decision to whether it is considered acceptable to continue the research.
Selective Breeding biological implications:
Selective breeding is crossing plants or animals with a desired gene together to create an offspring with the desired characteristic. This means that all the other “unwanted” characteristics are lost and the new population is extremely similar or inbred. This means there is less genetic diversity. In a genetically diverse population, everyone is different enough that they may not be susceptible to a specific disease or a particular environmental influence. It has shown that selective breeding programmes have yields and improved disease resistance. Breeders use the market demand to determine their breeding goals; this process is difficult as it is hard to predict consumers future desires. Although selective breeding can be extremely effective, there are disadvantages. There needs to be a large number of animals for the breeding process to be performed efficiently. Another disadvantage to selective breeding is that undesirable traits can be selected for by mistake. This can create excessive inbreeding, which leads to the production of sick or unproductive stock. It is useful to breed two completely different strains together. This results in extremely healthy offspring called hybrid vigor. Generally, hybrid vigor is only produced for a generation or two, however, cross breeding is a productive way of combating the disadvantages of inbreeding. Another disadvantage to selective inbreeding is during the production of the eggs and sperm, when the DNA of the parents is modified. This is called Meiosis. Meiosis is a process when the cells divide so that each one has half the normal number of chromosomes. Before this division occurs, the two pairs of chromosomes wrap around one another and crossing over occurs. Crossing over is when sections of one chromosome are swapped with sections of the other chromosome so new combinations are made. This is a disadvantage because it can mean that unexpected results can occur. An example of this is, the offspring from a homozygous recessive bull (the recessive gene is desired) crossed with a cow with “normal” genes will have one copy of the recessive gene. Once these offspring produce gametes, one of the recessive genes might migrate to a different chromosome, this means that the two traits aren’t expressed in one gamete. This means that the animal breeding process can be extremely slow especially compared to transgenesis, and it can take generations for the desired genes to be acquired.
Comparison and linking biological implications:
Talk about how similar and different the biological implications are.. Compare and contrast speeds of methods
Gene ourtside an orgaisms genome and breed it into another organisms gene pool
The evolution of selective breeding and transgenesis have been developing over a long time. They have improved livestock, and advanced animal and plant health and survival. The techniques in both methods encourage understanding and advance technology,but they are not without consequences and critics. Transgenesis and selective breeding can be seen as disrupting the natural order, creating moral and ethical concerns. As long as requisite guidelines and rules from superior agencies are followed by researchers to minimise negative impacts, the techniques of selective breeding and transgenesis could provide potential beneficial impacts for humans, animals and plants.
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