Angelman syndrome is a genetic disorder characterized by intellectaual and developmental delay, seizures, and other phenotypes. This syndrome can arise from mutations in the gene UBE3A, which is paternlly imprinted. If a child inherits a mutant allele of UBE3A from his mother and a wild type allele from his father, would this child have Angelman Syndrome. I know the the child would have the Angelman syndrome but why?

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Nelly StrackeLv2

19 Sep 2018

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A male patient age 15 comes into your clinic presenting the symptoms of mental retardation, behavioral abnormalities, including hand flapping and hyperactivity. Additionally, you notice this patient has some facial abnormalities, including large ears and a prominent jaw and forehead. Due to the mental retardation, you initially suspect that this disorder may be a trisomy of chromosome 21.

1. (2 points) Is trisomy 21 a chromosomal or single gene disorder? Please explain why.

2. (3 points) Please describe an experimental technique you could use to determine whether the patient has trisomy 21. Include in your description, what the experimental result would be if he did have trisomy 21, or he did not?

After performing the technique you described in question 2, you find out that he did not have the trisomy 21. You next ask the family if there are other members afflicted with the disorder and the answer is yes. Afterward, you get a full family history and put it together to form a pedigree.

After realizing that this is a single gene disorder, you believe the patient is suffering from Fragile X Syndrome. Answer the following questions below based on Fragile X syndrome.

4. (1 point) What gene is affected in Fragile X syndrome?

5. (1 point) Please create a list of symptoms a Fragile X patient may have?

6. (2 points) Based on the symptoms above, please discuss briefly why you may have been initially tricked into thinking this disorder was a chromosomal disorder.

7. (1 point) Please go to page 262 in your book, and explain in detail the nature of the mutation that causes Fragile X syndrome.

8. (2 points) Of the two techniques listed below, which would best allow you to state whether the patient has Fragile X syndrome? Please explain your answer.

a. PCR

b. RFLP

9. (2 points) Please answer question 9 using the information from questions 7 and 8. You analyze your data from the PCR reaction from question 8, which amplifies the region were the insertion lies. You notice that the patientâs sister has a single band on the gel at 45 base pairs. You notice the mother has a band at 200 base pairs and a band at 45 base pairs. The patient has a single band on the gel at 200 base pairs, and the father has a single band at 45 base pairs.

a. What is the genotype of the father and what is the phenotype of the sister?

b. Based on the experiment, what is the size of the insertion region in the wild-type allele, and what is the size of the insertion region in the mutant allele?

c. What is the actual size of the insertion (Hint: think about the difference in the sizes of the insertion region)

Questions 4-6. Sickle cell disease:
Sickle cell disease (sickle cell anemia) is a relatively common disorder in individuals of

African descent and affects approximately 1 in 500 African-Americans. Due to a mutation in an autosomal gene for hemoglobin, the homozygous recessive genotype leads to red blood cells that are relatively stiff and sticky, and deform into a sickle shape as they lose oxygen. This leads to problems in the spleen, and anemia.

There are hundreds of different hemoglobin alleles. Individuals heterozygous for the sickle cell allele and one non-sickle cell allele usually do not experience major complications or even noticeable symptoms. A genetic test is available to diagnose carriers.

James does not have sickle cell disease, neither does his mother or father, but his sister does. His wife Natasha does not have sickle cell disease, and neither of her parents does either. Natasha also has a sister who has sickle cell anemia and two brothers without the disease.

5.) If James and Natasha have a child, what is the probability that the child would be a homozygote for the recessive allele and have sickle cell disease? You may draw the Punnet square but please solve the problem using probability calculations, then explain your reasoning in 2-5 complete sentences.

cyanalligator893

In the October 2011 issue of PLoS Genetics, Pierson et al. used whole-exome sequencing to identify the mutations responsible for a rare spastic ataxia-neuropathy syndrome. The paper and supporting information can be found at http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1002325, and you will need to access the paper to answer these questions. The paper is focused primarily on the phenotype and the particular gene, but our attention will be primarily on the methods used for the exome-sequencing approach, which is found in the Methods and in the Supporting Information.

a. Figure 1A shows a pedigree of the family with two affected sons, who are not identical twins.

i. Recalling pedigree analysis from your introductory genetics course, what is the most likely mode of inheritance for this syndrome?

ii. What is the probability that the next child born to this couple will be disease-free?

b. Summarize the experimental strategy that yielded the results shown in Supplemental Table S2, as found under Supporting Information. Your summary should define the abbreviations used in the column headings and what the numbers mean. You should also include an explanation of why the numbers decrease as one reads from left to right from columns 2 through 6 (not including Total Protein Coding Exons Sequenced). c. The numbers of candidate genes in Supplemental Table S3 are 71 and 7, but these numbers do not appear anywhere in Supplemental Table S2. What inference from the data was made that allowed the investigators to arrive at the numbers in Table S3 based on the numbers in Table S2?

d. What further inferences led the investigators to conclude that AFG3L2 is the gene most likely responsible for this syndrome?

e. In the analysis of Miller Syndrome described in the chapter, the affected children did not have the same mutation on each homologous chromosome, and were in fact heteroallelic for the mutations. In this example, the children have the same mutation on each homologous chromosome. Why did the authors expect that the affected children would be homozygous for the same mutation?

f. What is the postulated mechanism by which this mutation results in this phenotype?

g. In this chapter, genes can be cloned and identified based on the following five properties: map position, mutations and allelic differences, expression patterns, complementation testing, and homology with genes in other organisms. Using a flow chart, diagram how these five properties led to the identification of the gene for this syndrome.