Researchers have identified a gene in humans that (when mutant) causes severe dw

Question

Researchers have identified a gene in humans that (when mutant) causes severe dwarfism and mental retardation. This disorder is inherited in an autosomal recessive manner, and the mutant allele is known to be a loss-of-function mutation. The same gene has been found on mice, although a mutant version of the gene has not been discovered in mice. To develop drugs and an effective therapy to treat this disorder, it would be extremely useful to have a mouse model of the disorder. In other words, it would be desirable to develop a strain of mice homozygous for a loss-of-function mutation in the mouse gene. Experimentally, how would you develop such a strain? List all of the steps necessary to accomplish this. A form of dwarfism known as Ellis-van Creveld syndrome was first discovered in the late 1930's, when Richard Ellis and Simon van Creveld shared a train compartment on their way to a pediatrics conference, and discovered they each had a patient with this syndrome. They published a description of the syndrome in 1940. Affected individuals have a short-limbed form of dwarfism and often have defects of the lips and teeth, and Polydactyly (extra fingers). The largest pedigree for the syndrome was reported in an Old Order Amish population in eastern Pennsylvania in 1964. In this community with a population of 8000, the observed frequency is 2 per 1000. All affected individuals have unaffected parents, and all affected cases can be traced back to Samuel King and his wife, who arrived in the area in 1774. Neither King nor his wife was affected with the disorder. There are no known cases of the disorder in other Amish communities, such as those in Ohio and Indiana. From the information given, hypothesize the most likely mode of inheritance (Dominant or recessive? Autosomal or X-linked?) for this disorder. Determine the frequency of the wild-type and Ellis-van Creveld alleles, and calculate the genotype frequencies in the population. What is the most likely explanation for the high frequency of the disorder in the Pennsylvania Amish communities?

Explanation / Answer

The gene is recessive because the parents will not be affected and both of the carriers have a child that containing disorder.

Autosomal recessive disorders are the kind of disorders in which the affected person is consisting of 2 mutant alleles.

The parents of the affected person will not be affected and the chance for next affected child is 25%. Whereas affected child having normal sibling is having carries probability of 2/3 and both of their childrens are affected if both of their parents will be affected.EVS syndrome is an autosomal recessive pattern.

The population of the recessive phenotype is probably the parents form the same family. And if some is affected from autosomal disorder then it relates that the parents are from small villages.

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