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?

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?

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Description: 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 ha

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 6QP: Although it is well known that X-rays cause mutations, they are routinely used to diagnose medical...

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Researchers have identified a gene in humans that (when mutated) causes tremors and unstable walking due to neurological problems. This disorder is inherited in an autosomal recessive manner, and the mutant allele isknown to result from a loss-of-function mutation. The same gene hasbeen found in mice, although a mutant mouse version has not beendiscovered. To develop an effective drug therapy to treat this disorderin humans, it would be experimentally useful to have a mouse model.In other words, it would be desirable to develop a strain of mice thatcarry the mutant allele in the homozygous condition. How would youdevelop such a strain?
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?
A rare dominant mutation expressed at birth was studiedin humans. Records showed that six cases were discoveredin 40,000 live births. Family histories revealed that in twocases, the mutation was already present in one of the parents.Calculate the spontaneous mutation rate for this mutation.What are some underlying assumptions that may affect ourconclusions?
The family of a sixth-grade boy in Palo Alto, California, wasinformed by school administrators that he would have to transferout of his middle school because they believed his mutation ofthe CFTR gene, which does not produce any symptoms associatedwith cystic fibrosis, posed a risk to other students at the schoolwho have cystic fibrosis. After missing 11 days of school, a settlementwas reached to have the boy return to school. What ethicalproblems might you associate with this example?
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?
Mouse models for human genetic diseases are potentially powerful tools to help geneticists understand thecause of the aberrant phenotypes and develop newtherapeutic measures. However, such mice are not always as useful to investigators as it might seem at firstglance. Suppose that you have a mouse knockoutmodel for a human disease caused by homozygosityfor a null allele of a gene. Discuss how the followingsituations might complicate investigations of the human disease based on this mouse model.a. Mice have a shorter life span than humans.b. Mice homozygous for certain knockout mutationsdie in utero.c. Mouse genomes may have additional copies of thegene whose mutation causes the disease in humans.
Mouse models for human genetic diseases are potentially powerful tools to help geneticists understand thecause of the aberrant phenotypes and develop newtherapeutic measures. However, such mice are not always as useful to investigators as it might seem at firstglance. Suppose that you have a mouse knockoutmodel for a human disease caused by homozygosityfor a null allele of a gene. Discuss how the followingsituations might complicate investigations of the human disease based on this mouse model.a. Mice have a shorter life span than humans.b. Mice homozygous for certain knockout mutationsdie in utero.c. Mouse genomes may have additional copies of thegene whose mutation causes the disease in humans.d. Mice from different inbred lines homozygous forthe same gene knockout vary in the penetrance andexpressivity of the phenotype.e. Manipulations to create the knockout mouse, suchas the presence of a drug resistance gene that allowsthe selection of cells containing the knockout (seeFig. 18.9),…
Like Hurler syndrome, Fabry disease involves an abnormal accumulationof substances within lysosomes. However, the lysosomesof individuals with Fabry disease show an abnormal accumulationof lipids. The defective enzyme is α-galactosidase A, which is alysosomal enzyme that functions in lipid metabolism. The enzymaticdefect causes cell damage, especially to the kidneys, heart,and eyes. The gene that encodes α-galactosidase A is found on theX chromosome. Let’s suppose a phenotypically unaffected coupleproduces two sons with Fabry disease and one phenotypicallyunaffected daughter. What is the probability that the daughter willhave an affected son?
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?
Diamond–Blackfan anemia (DBA) is a rare, dominantgenetic disorder characterized by bone marrow malfunction,birth defects, and a predisposition to certaincancers. Infants with DBA usually develop anemia in the firstyear of life, have lower than normal production of red blood cellsin their bone marrow, and have a high risk of developing leukemiaand bone cancer. At the molecular level, DBA is causedby mutations in any one of 10 genes that encode ribosomalproteins. The first-line therapy for DBA is steroid treatment,but more than half of affected children develop resistance tothe drugs and in these cases, treatment is halted. DBA can betreated successfully with bone marrow or stem cell transplantsfrom donors with closely matching immune system markers.Transplants from unrelated donors have significant levels ofcomplications and mortality. Given that a faulty ribosomal protein is the culprit and causesDBA, discuss the possible role of normal ribosomal proteins.Why might bone marrow cells be…
Diamond–Blackfan anemia (DBA) is a rare, dominantgenetic disorder characterized by bone marrow malfunction,birth defects, and a predisposition to certaincancers. Infants with DBA usually develop anemia in the firstyear of life, have lower than normal production of red blood cellsin their bone marrow, and have a high risk of developing leukemiaand bone cancer. At the molecular level, DBA is causedby mutations in any one of 10 genes that encode ribosomalproteins. The first-line therapy for DBA is steroid treatment,but more than half of affected children develop resistance tothe drugs and in these cases, treatment is halted. DBA can betreated successfully with bone marrow or stem cell transplantsfrom donors with closely matching immune system markers.Transplants from unrelated donors have significant levels ofcomplications and mortality. While a stem cell transplant from an unaffected donor is currentlythe only cure for DBA, genome-editing technologies mayone day enable the correction of…
Among mammals, measurements of the rate of generation of autosomal recessive mutations have been madealmost exclusively in mice, while many measurementsof the rate of generation of dominant mutations havebeen made both in mice and in humans. What do youthink is the reason for this difference?