Researchers have successfully used gene therapy toameliorate some human genetic diseases by adding anormal gene copy to cells whose genomes originallyhad only nonfunctional mutant copies of that gene.For example, a form of blindness due to the lack of asingle protein called RPE65 has been reversed byintroduction of a normal RPE65 gene to cells of theretina of adults.a. The success of this gene therapy approach providesus with clues about the role of the RPE65 proteinin the retina. Do you think that RPE65 is neededfor the proper development of the human eye?b. Can you see a potential difficulty in applying this genetherapy approach for diseases like microcephaly?

Researchers have successfully used gene therapy toameliorate some human genetic diseases by adding anormal gene copy to cells whose genomes originallyhad only nonfunctional mutant copies of that gene.For example, a form of blindness due to the lack of asingle protein called RPE65 has been reversed byintroduction of a normal RPE65 gene to cells of theretina of adults.a. The success of this gene therapy approach providesus with clues about the role of the RPE65 proteinin the retina. Do you think that RPE65 is neededfor the proper development of the human eye?b. Can you see a potential difficulty in applying this genetherapy approach for diseases like microcephaly?

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter11: Genome Alterations: Mutation And Epigenetics

Section: Chapter Questions

Problem 10QP: If the coding region of a gene (the exons) contains 2,100 base pairs of DNA, would a missense...

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Mutations in the CFTR gene result in cystic fibrosis in humans, a conditions in which abnormal secretions are present in the lungs, pancreas, and sweat glands. The gene was mapped to a 500-kb region on chromosome 7 containing 3 candidate genes. a)Using your knowledge of the disease symptoms, how would you distinguish between the candidate genes to decide which is most likely to encode the CFTR gene? b)How would you prove that your chosen candidate is the CFTR gene?
In the study of plants and animals, it is relatively common forresearchers to identify a gene using molecular techniques withoutknowing the function of the gene. In the case of mice, the functionof the gene can be investigated by making a gene knockout. Aknockout that causes a phenotypic change in the mouse may providean important clue regarding the function of a gene. For example,a gene knockout that produced an albino mouse would indicate that the knocked-out gene probably plays a role in pigment formation. The experimental strategy of first identifying a gene based on its molecular properties and then investigating its function by making a knockout is called reverse genetics. Explain how this approach is opposite to (or the reverse of) the conventional way that geneticists study the function of genes.
Two genes associated with breast cancer, BRCA1 and BRCA2, were discovered in 1994 and 1995, respectively, and shortly thereafter, were patented by Myriad Genetics, a company based in Utah. Under the patents, testing for mutations in these genes could only be performed by Myriad, at costs from 300 to 3,000. Myriad also patented the process of analyzing the results of such tests, preventing anyone who obtains the sequence of their BRCA genes by other means (which itself would probably be patent infringement) from interpreting the information. The idea that genes can be patented has been a contentious issue from the beginning. Patents are not granted for products of nature, meaning that genes inside the body are not patentable, but biotech companies successfully argued that by removing a gene from the human body, purifying it, and then obtaining its DNA sequence, they created something not found in nature, and which is therefore a patentable invention. The U.S. Patent Office found the argument persuasive, but opponents argue that genes are parts of our bodies and can be identified but not invented. Biotech companies argue that without the protection offered by patents, they would have no incentive for research and development of diagnostic tests. In Europe, patents for BRCA1 and BRCA2 were revoked in 2004 because they did not meet the standards for a patent. After more than a decade of legal disputes, the patents were partially restored in 2008 on a very restricted basis. In the United States, a lawsuit, focused on the patents for the BRCA genes, was filed in May 2009. The suit challenges the basic idea that genes are patentable. In November 2009, the judge ruled that the lawsuit can proceed, and the case is moving forward. In March 2010, a federal court invalidated Myriad Genetics patent on these genes. In August 2011, the U.S. Court of Appeals reversed the lower courts decision and ruled that gene sequences isolated from cells are not a product of nature and are therefore patentable. The case went to the U.S. Supreme Court, which ordered the appeals court to reconsider the case. The Federal Appeals Court did not change its decision, and the case once again, went to the U.S. Supreme Court. A unanimous decision in June 2013 invalidated Myriads patents on the basis that isolating a gene from nature does not make it patentable. This is a landmark decision on gene patenting with widespread ramifications for the biotechnoloogy industry. Will this decision reduce the incentives for companies to invest in new diagnostic tests that would be used by cancer victims or those with serious genetic disorders?
If the coding region of a gene (the exons) contains 2,100 base pairs of DNA, would a missense mutation cause a protein to be shorter, longer, or the same length as the normal 700 amino acid proteins? What would be the effect of a nonsense mutation? A sense mutation?
Although it is well known that X-rays cause mutations, they are routinely used to diagnose medical problems, including potential tumors, broken bones, and dental cavities. Why is this done? What precautions need to be taken?
The following is a list of mutations that have beendiscovered in a gene that has more than 60 exons andencodes a very large protein of 2532 amino acids.Indicate whether or not each mutation could cause adetectable change in the size or the amount of mRNAand/or a detectable change in the size or the amountof the protein product. (Detectable changes in size oramount must be greater than 1% of normal values.)What kind of change would you predict?a. Lys576Val (changes amino acid 576 from lysineinto valine)b. Lys576Argc. AAG576AAA (changes codon 576 from AAG toAAA)d. AAG576UAGe. Met1Arg (at least two possible scenarios exist forthis mutation)f. promoter mutationg. one base pair insertion into codon 1841h. deletion of codon 779i. IVS18DS, G–A, + 1 (this mutation changes thefirst nucleotide in the eighteenth intron of the gene,causing exon 18 to be spliced to exon 20, thusskipping exon 19)j. deletion of the poly-A addition sitek. G-to-A substitution in the 5′ UTRl. insertion of 1000 base…
You have isolated a protein that binds to DNA in theregion upstream of the promoter sequence of the sysgene. If this protein is a positive regulator, which ofthe following would be true?a. Loss-of-function mutations in the gene encodingthe DNA-binding protein would cause constitutiveexpression of sys.b. Loss-of-function mutations in the gene encodingthe DNA-binding protein would result in little orno expression of sys.
In the treatment of cancer, the basis for many types of chemotherapyand radiation therapy is that mutagens are more effective at killingdividing cells than nondividing cells. Explain why. What are possibleharmful side effects of chemotherapy and radiation therapy?
Over a period of several years, a large hospital kepttrack of the number of births of babies displaying thetrait achondroplasia. Achondroplasia is a very rareautosomal dominant condition resulting in dwarfismwith abnormal body proportions. After 120,000births, it was noted that 27 babies had been born withachondroplasia. One physician was interested in determining how many of these dwarf babies resultedfrom new mutations and whether the apparent mutation rate in this geographical area was higher thannormal. He looked up the families of the 27 dwarfbirths and discovered that four of the dwarf babieshad a dwarf parent. What is the apparent mutationrate of the achondroplasia gene in this population? Isit unusually high or low?
Researchers have identified a gene in humans that (when mutant)causes severe dwarfism and mental impairment. This disorder isinherited in an autosomal recessive manner, and the mutant alleleis known to be a loss-of-function mutation. The same gene hasbeen found in mice, although a mutant version of the gene has notbeen discovered in mice. To develop drugs and an effective therapyto treat this disorder in humans, it would be experimentallyuseful to have a mouse model. In other words, it would be desirableto develop a strain of mice that carry the mutant allele in thehomozygous condition. Experimentally, how would you developsuch a strain?
The origin of new β cells of the pancreas—fromstem cells or from preexisting β cells—was not resolveduntil a decade ago, when the technique of lineage tracingwas used to decide the issue. Using transgenic mice thatexpressed a tamoxifen-activated form of Cre recombinaseunder the control of the insulin promoter, which is activeonly in β cells, investigators could remove an inhibitorysegment of DNA and thereby allow expression of humanplacental alkaline phosphatase (HPAP), which can bedetected by histochemical staining. After a pulse of tamox-ifen that converted about 30% of β cells in young mice to cells that express HPAP, the investigators followed the per-centage of labeled β cells for a year, during which time thetotal number of β cells in the pancreas increased by 6.5-fold. How do you suppose the percentage of β cells wouldchange over time if new β cells were derived from stemcells? What if new β cells were derived from preexistingβ cells? Which hypothesis do the results in Figure…
(a) Did deletion of any of the possible control elements cause anincrease in reporter gene expression relative to the control? If so,which one(s), and how can you tell? (b) If loss of a control elementcauses an increase in gene expression, what must be the normalrole of that control element? Propose a biological explanation forhow the loss of such a control element could lead to an increase ingene expression.