Antibiotics against Viruses - Assignment Example

Genetics s 1. A blood transfusion is incompatible when the donors blood type is AB- and the recipients blood type is O+. Explain: O+ recipient’s blood has no antigens on the surface of the RBC but the serum has antiA and anti B antibodies therefore it cannot receive blood from AB type since it will lead to agglutination. Moreover, it has a + RH factor while the donor has – RH factor however this would not cause much problem. 2. Antibodies important to the immature immune systems of newborn human infants are EXPLAIN b. The most important antibodies are IgG and IgD. Mother passes IgG to foetus which protects it from bacteria, viruses and toxins. However IgD is also important since it protect the body from pathogens for production of antibodies in infants 3. Which of the following characteristics is not typical of cancer cells? Explain: c. they are heritable Cancer cells are not heritable since mutations in normal cells causes abnormal cancerous growth however this is not passed down from one generation to another.even though today cancer is considered a genetic phenomena yet it is not heritable. 4. Which of these genetic tests will confirm whether a newborn has a cystic fibrosis genotype? Explain: b.prenatal screening Prenatal screening is employed by counsellors to detect if the off springs would inherit the problem or not. 5. The polymerase chain reaction has applications in Explain: PCR has application in all of the above. In forensics PCR is used to amplify DNA sequences that are used to establish blood relations, identify remains or convict a criminal. In fields such as environmental, agriculture, veterinary the technology is used to amplify DNA or RNA of pathogens to some detectable levels. Again in genetics it finds application as a diagnostic tool. 6. Match each descriptor or example in the right hand to the best term in the left hand colum.Use only one descriptor per term and only one term per descriptor. ANSWER: Term description 1.fever e. stronger phagocytic attack 2.innate immunity j. interferon and interleukins 3.Mab i. antibody used to target specific tissue 4.Telomerase b. single nucleotide polymorphism 5.sporadic cancer g. somatic mutations 6.electroporation h. delivery of a gene to a cell 7.electrophoresis c. separation of DNA fragments 8.gene targetting f. delivery of a gene to a specific location 9.positional cloning a. RNA template for DNA synthesis 10.comparative genomics d. evolutionary relationships 7. The human immune system has developed diverse, coordinated methods of resisting and destroying viruses. a. Describe the typical composition of a virus. Why are viruses not classified as living organisms? (3 marks) A virus consists of a single stranded or a double stranded RNA or DNA enveloped in a protein coat. In some types an outer covering may also be present. Viruses are not classified as living organisms since they are not active outside a host i.e they do not grow, metabolize or reproduce outside host cell and can only reproduce when they enter a host and use the host’s machinery. b. Why are antibiotics ineffective against viruses? What characteristics do antibiotics specifically target, and why is this advantageous to humans? (3 marks) Antibiotics are derived from bacteria and are ineffective against virus. Antibiotics work my blocking metabolic pathways in bacteria however a virus lacks metabolic pathways and is dependent on host. c. HIV has characteristics, such as a high rate of mutation, that enable it to evade the human adaptive immune response. Describe why it mutates faster than human nuclear DNA. (3 marks) The HIV has a high rate of mutation and changes faster than human nuclear DNA because of the fact that the virus does not have the ability to repair replication errors and the errors happen very frequently at a rate of 1 in 5000 base pairs owing to the errors committed by the reverse transcriptase enzyme while copying RNA into DNA. d. Lewis states, “First, HIV enters macrophages, impairing this first line of defense” (2008, p. 339). This is not quite true. To get this far, HIV managed to get through the “real” first line of defense. What is this first line? Give two examples of its methods. (3 marks) The real first line of defence are the physical and chemical barriers such as skin, hair etc. In order to get to the macrophage s the virus needs to cross the mucosal lining. Two methods by which the virus does so is firstly by contact with skin mucosa which is broken down as HIV enters the cells by destroying the lipid raft. Another method is that it can cross the placental barrier thereby easily infecting developing embryos. 8. What would be the likely immune response ability of an individual with a deletion of a Class II gene of the MHC on one chromosome and a nonsense mutation at the beginning of the same gene on the homologue? (4 marks) Since in the chromosome Class II MHC is deleted and its homologue also has a non-sense mutation there will be major problems with immunity response. Since MLA class II genes encode human leukocyte antigens its deletion would mean that the proteins that are found on antigen presenting cells would not be produced. Since antigen processing and presentation is the first step of antigen response immunity will be affected a bit even though class I genes will be working. Moreover, since the homologue has non-sense mutation the proteins encoded there would also not be produced at all. 9. A completely new protein has been synthesized by a research lab. You are inadvertently exposed to it and have an allergic response. What type of antibody initiates this response? How can your body make antibodies to a new antigen? (4 marks) If I am exposed to the new antigen and have an allergic reaction both my humoral and cellular immunity barriers are involved in the response. Antibodies belonging to class IgE initiate the response and bind to the mast cells which induce the opening of these mast cells to release allergy mediators such as histamine and heparin. These allergy mediators causes inflammation and other responses such as runny eyes, fever, etc. Once I am exposed to the new type of antigen, the B cells of my body would produce antibodies aginst the antigen. These antibodies would continue to exists. 10. Viruses can cause an increase in the rate of transcription of proto-oncogenes in at least two ways: directly and indirectly. Describe these two modes. (6 marks) The rate of transcription of proto-oncogene is enhanced by two ways. It may be enhanced when the proto-oncogene is placed near a gene that boosts its expression .For example a virus might insert its DNA into a gene next to the proto-oncogene. When this viral DNA is transcribes the proto-oncogene is also transcribed rapidly. Another way in which the rate maybe increased is when the proto-oncogene is moved next to a gene which already has a high rate of transcription. This normally happens when inversion or translocation of chromosome takes place .For example, cancer of the parathyroid gland is associated with inversion of chromosome 11. This inversion places a proto-oncogene near the DNA sequence which is responsible for transcription. When the hormone is expressed the oncogenes is expresses as well. 11. Give two reasons why a cancer associated with an inherited damaged p53 allele is not considered an autosomal recessive Mendelian trait. (4 marks) A cancer associated with inherited damage p53 is not considered autosomal recessive because in most cases it is found in somatic cells only. However, even if the mutation is found in the germ line, there high risk of cancer development. Therefore, somatic mutation in p53 will always result in cancer since the mutation is already present in the germ line cells as well. While in order to be autosomal recessive it is important that the mutated allele to be masked by the other allele but in case of p53 it is not so since the presence of the mutation actually enhances the risk of cancer development. 12. Explain why a gain of function would be a dominant effect and a loss of function would be a recessive effect. Which types of genes are each associated with: oncogenes or defective tumour suppressor genes? Why? (5 marks) Answer: A gain of function would be a dominant effect while a loss of function would be a recessive effect because a recessive trait causes loss of normal protein function causing loss of function. However, in gain of function abnormal proteins are produced that interfere with action of normal protein. Oncogenes are associated with gain of function while tumour suppressor genes are associated with loss of function. Oncogenes are associated with gain of function since the action of the gene changes in certain ways and initiated abnormal growth and production while in case of tumour suppressing genes since the gene reduces a certain product or function it is said to be associated with loss of function. 13. What negative role does the environment play in causing cancer? What positive effects can the environment have? (3 marks) Environmental factors play an important role in cancer since they have the ability to facilitate mutation or alteration of genes. Long time exposure to certain substances may induce mutation causing cancer. Farmers on chronic exposure to insecticides developed translocations and suffered from Hodgkin’s lymphoma. Another way in which environment palsy a negative role is through excess sun exposure leading to skin cancer. However, environment may also have some positive effects as well when it comes to cancer. Vitamin D and other natural chemicals such as folic acid, selenium from tomato and green tea have cancer fighting properties. 14. Identify four naturally occurring enzymes important to DNA technologies, and describe an example for each of their natural and technological uses. (10 marks) Four naturally occurring enzymes important to DDNA technologies include: a. Taq Polymerase b. Reverse transcriptase c. Ligase d. Restriction endonuclease Taq polymerase- It is found in bacteria and is a heat stable enzyme.The role of any polymerase enzyme is to create DNA by arranging bases. It plays an important role in PCR technology as it can withstand high temperature. Reverse transcriptase- This enzyme is used to generate complementary DNA from RNA by the process of reverse transcription. It is used in RDT for reverse transcription in generation of cDNA. Ligase- Ligase helps in joining of two DNA strands by formation of phosphodiester bond between them. Ligase enzyme plays an important role in Recombinant DNA technology since it is used to join the sticky ends of DNA into a single recombined DNA strand. Restriction endonuclease- These enzymes cut DNA stands at particular sites. These are used in DNA technology to cut DNA strands and obtain a specific sequence. 15. Match each of the methods or vectors below to an appropriate form of gene therapy, assigning two methods or vectors to each form. Use each method or vector only once. (6 marks) Methods/vectors: particle bombardment, microinjection, liposome, electroporation, virus, chemical hole formation. Forms of gene therapy: in vivo, in situ, ex vivo Answer: Forms of Gene Therapy Methods In vivo Virus, microinjection Insitu liposome, chemical hole formation Ex vivo electroporation, particle bombardment 16. Identify and compare the methods of somatic gene therapies for ADA deficiency described on pp. 404‑405 (Lewis) and OTC deficiency described on pp. 405-406 (Lewis). (6 marks) The somatic gene therapy used for treating ADA deficiency is ex-vivo in nature. The cells are removed to the outside and therapeutic genes are added and these cells are returned to the body for proper functioning. In case of OTC, in—vivo was used. This method utilized the adenovirus to transfer the genes to the cells. In this case the adenovirus was inserted with the functional OTC gene and the virus was then transferred to the patient’s body. 17. Compare a genetic cause of male infertility to a genetic cause of female infertility. (4 marks) Most of the male infertility are genetic in nature. In such males, some portion of the Y chromosome is deleted which means removal of important genes which control the process of spermatogensis. In the female, ovulation may also be hampered owing to genetic defects .Hormonal imbalance underlies the problem of irregular ovulation. For example genetic problem may induce over secretion of prolactin which inhibits ovulation thereby hampering production of egg cells. 18. Describe the uses, process, and outcome of PGD. (6 marks) PGD or Preimplantation genetic diagnosis are tests that can detect genetic and chromosomal abnormalities before the pregnancy starts. In this process the couple selects a very early preimplanation embryo. This embryo would be the first one to arrive and implant itself in the uterus. From the blastomeres of 8 cells, 1 cell is removed for testing while the other 7 cells complete the process of normal development. The single cell taken from the blastomeres is karyotyped or the DNA is probed for genes. This enables researchers to detect any problem even before the blastomeres attaches to the uterine wall. Even though PGD has had its problems with human ethics it is an important diagnostic tool to ensure more live and normal births.PGD is also used for sex selection only for the purpose of determining sex linked disorders. 19. Research methods used in studying a genetic disease change with technological advances. These changes can be seen in Reading 22.1: Discovering the Huntington Disease Gene, which describes the integrated Mendelian and molecular approaches in the investigation of Huntington disease. Briefly summarize the molecular studies. (5 marks) Answer: With advent of technology genetic studies are today used widely and can be conducted in a few hours. Molecular approaches were used to detect mutations within the Huntington’s diseases gene within a family. DNA samples were taken from members of a family. Out of the 41 members of which 21 were suffering from the disease. The DNA samples were cut using restriction endonuclease enzymes and were then treated with DNA labelled probes that bound only to the DNA of those suffering from the diseases. This attachment of the probe revealed the RFLP (restriction fragment length polymorphism) which showed the sequence which was unique to HD patients. Further research on probe data revealed that G8 probe bound only to DNA of HD patients until the G8 gene was finally discovered and it was known that mutation in G8 caused the problem. The next step was to pinpoint the location of the gene on the chromosome; researchers used hybrid human/rodent cells each containing one human chromosome. The cell containing G8 had the chromosome number 4 which meant that g8 was present in chromosome 4. Read More