Concept explainers
Duchenne muscular dystrophy (DMD; OMIM 310200) and Becker muscular dystrophy (BMD; OMIM 300376) are both X-linked recessive conditions that result from different mutations of the same gene, known as dystrophin, on the long arm of the chromosome. BMD and DMD are quite different clinically. DMD is a very severe disorder that first appears at a young age, progresses rapidly, and is often fatal in the late teens to 20s. BMD, on the other hand, is much milder. Often symptoms don’t first appear until the 40s or 50s, the progression of the disease is slow, and fatalities due to BMD are infrequent. Go to https://www.ncbi.nlm.nih/omim and survey the information describing the gene mutations causing these two conditions. Discuss the information you find with a few others in a small group, and write a single summary explaining your findings.
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Genetic Analysis: An Integrated Approach (3rd Edition)
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- In man, muscular dystrophy is a condition in which the muscles waste away during early life and may result in a shorter life expectancy. It is due to a sex-linked, recessive gene. A certain couple has five children – three boys (ages 1yr, 3yrs, and 10yrs old) and two girls (ages 5yrs and 7yrs old). The oldest boy shows the symptoms of this disease. You are their family physician and they come to you for advice. What would you tell them about the chances of their other children developing the disease?arrow_forwardThere are six types of agglutinogen named C,D, E and c,d,e.the first three are dominant and last three are recessive.discussarrow_forwardCampomelic dysplasia (CMD1) is a congenital humansyndrome featuring malformation of bone and cartilage.It is caused by an autosomal dominant mutation of agene located on chromosome 17. Consider the followingobservations in sequence, and in each case, draw whateverappropriate conclusions are warranted.(a) Of those with the syndrome who are karyotypically46,XY, approximately 75 percent are sex reversed,exhibiting a wide range of female characteristics.(b) The nonmutant form of the gene, called SOX9, isexpressed in the developing gonad of the XY male,but not the XX female.(c) The SOX9 gene shares 71 percent amino acid codingsequence homology with the Y-linked SRY gene.(d) CMD1 patients who exhibit a 46,XX karyotypedevelop as females, with no gonadal abnormalities.arrow_forward
- How does a positive ASO test for sickle-cell anemia determine that an individual is homozygous recessive for the mutation that causes sickle-cell anemia?arrow_forwardIn humans, hemophilia is an X-linked recessive disorder that affects the gene for factor VIII protein, which is essential for blood clotting. The dominant and recessive alleles for the factor VIII gene are represented by H and h. Albinism is an autosomal recessive condition involving the tyrosinase enzyme which synthesizes pigment. Alleles of tyrosinase are represented by A and a. The provided pedigree shows a new marriage between Clara and Charles. A) Review the pedigree, filling in any genotypes that can be determined from the displayed traits. B) What is the probability that their first child will display hemophilia, albinism, or BOTH hemophilia AND albinism.C) If Clara and Charles first child has albinism, what is the probability that the second child will also display albinism?arrow_forwardThe karyotypes shown here depict chromosomal abnormalities. Name the syndromes and if they are male or female?arrow_forward
- Concordance studies of twins for a neurodegenerative disorder show MZ= 46% and DZ= 15%. Further studies have shown a possible link to a gene on chromosome 9, however, there are some individuals in the study who have the allele but do not develop the disorder (group 1), and there are other individuals who do not have the allele yet develop the disorder (group 2). Amita's older sister and maternal uncle have this disorder. Currently, Amita & her 2 younger brothers do not show symptoms. Amita's paternal grandfather was rumored to have this disorder. 1. Draw the pedigree for Amita's family and determine the mode of inheritance if any. 2. Explain how the 2 groups in the study could be possible? 3. What would you tell Amita about the heritability of this disorder?arrow_forwardMany genetic disorders exhibit locus heterogeneity. Define andgive two examples of locus heterogeneity. How does locus heterogeneityconfound a pedigree analysis?arrow_forwardImagine that individual V-8 marries a female cousin who is a carrier of the 5αRD mutation. What is the probability that they will have a child who has the disorder? answer should be a fraction.arrow_forward
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