Question 1: Identify the mutation gene of Spinocerebellar ataxia 1 ( SCA1) genet

Question

Question 1: Identify the mutation gene of Spinocerebellar ataxia 1 ( SCA1) genetic disease.

Question 2: Indicate what the squares and circles represent and what is the difference between filled and hollow shapes in the Tracing family history map.

Question 3: Discuss what conclusions can be drawn from the pedigree eg assuming that the disease is caused by the mutation of one single gene, do you think this mutation is recessive or dominant? Are the affected individuals more likely to be heterozygous or homozygous for this mutation? Is the disease affecting equally men and women? explain how it is supported by the pedigree.

 Question 4: indicate what genetic mutation is responsible for the SCA1 disease and what consequence it has on protein primary structure.

Question 5: Which organ and cell type are primarily affected by the mutation? Is this consistent with the symptoms observed in SCA1 patients?

Mouse models of SCA1 have been developed and helped researchers to understand this disease and to experiment new treatments.

Question 6: Describe the phenotype of the SCA1 mouse. Is it similar to symptoms observed in SCA1 patients?

Question 7: Is SCA1 considered to be caused by a loss of function of the protein affected, or is it thought to be due to another mechanism?

Question 8: Researchers then developed an SCA1 model in Drosophila – what are the advantages of using a Drosophila model over a mouse one

Question 9: Using the Drosophila model of SCA1, what was the protein kinase they found to be implicated in SCA1 associated neurodegeneration and why is this knowledge useful with respect to treating the disease?

Explanation / Answer

2.      In family history map or pedigree chart,

a.       the circle represents the female

b.      square represents the male

c.       filled shape shows genetic drift while blank shows no genetic drift.

3.      Pedigree chart id symbolic representation of the manifestation and occurrence of phenotypes of a gene or organism and its ancestors from one generation to the next, mostly in the human.

a.       If a mutation occurred in a single gene, it will be heterozygous, and in this case, the recessive gene will not be expressed but dominant gene shall be expressed.

b.      If a mutation occurred in a single gene, it is likely to heterozygous, because to be homozygous, mutation should be in both alleles.

c.       Depending, up on the location of the gene in the chromosome, it can be decided that whether or not it will affect either sex equally? If it is present on the sex chromosome, then the condition shall be affected.

d.      Pedigree shall be helpful in predicting the chances of occurrence of affected gene in a particular generation.

4.      A heterozygous abnormal CAG trinucleotide expansion in ATXN1 gene; 6p (Ataxin 1), which contains an abnormally lengthened stretch of the amino acid glutamine.

5.      The problem is observed as neurodegenerative disease considered by a progressive loss of cerebellar neurons, particularly Purkinje neurons. SCA1 has no specific clinical phenotypes however, it usually characterized by considering family history along with, progressive cerebellar ataxia, Dysarthria and eventual deterioration of bulbar functions.

6.      The symptoms were closely related to mouse and is characterized motor incoordination, cognitive deficits, wasting, and premature death, accompanied by Purkinje cell loss and age-related hippocampal synaptic dysfunction.

7.       SCA1 is caused by the affected Ataxin 1 protein.

8.      Drosophila has an advantage of genetic screens which revealed that genes encoding proteins involved in RNA metabolism and transcription regulation modify the development of SCA1.

9.      In Drosophila TXN1 has been interacting with the transcription repressor Capicua through the AXH domain and modulate its activity in Drosophila and mammalian cells provided an opportunity in the direction of treatment.

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