mahendra
Forum Guru
Topics: 173
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A six-month-old baby girl who was normal at birth, begins to show signs
of motor retardation. While she could sit up at 5 months, she can no longer
do so. As time goes on, the child continues to deteriorate, and eventually
becomes unresponsive to visual or auditory stimuli. Funduscopic
examination reveals cherry-red macular spots in both eyes. Which
of the following genetic abnormalities is most often related to the
development of this disease?
A. Confined placental mosaicism
B. Expanded trinucleotide repeat
C. Frameshift mutation
D. Nondisjunction
E. Translocation
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| leftfoot
Forum Elite
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Posts: 216
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donno the answer ...but case described sounds like tay-sachs( def of lysosomal enzyme hexosaminidase A)
whats the genetic mechanism???
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| asmi
Forum Hero
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Posts: 4,609
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yess i too don't know exactly what is the answer apart from that its a lysosomal storage disease.
How do you differentiate it from retonoblastoma ?
If it is retinoblastoma than answer could be E.
Iam confused :roll:
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| mahendra
Forum Guru
Topics: 173
Posts: 419
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ANS IS C
Most cases of Tay-Sachs disease are caused by insertion of four nucleotides into the coding region of the gene for the alpha-subunit of the hexosaminidase A gene. This produces a frameshift mutation, resulting in the creation of a premature stop codon downstream from the inserted nucleotides. The disease presents as described in the question, and is more common in Ashkenazi Jews. The carrier rate in this population is 1 in 25. There is presently no effective treatment and survival beyond four years of age is rare.
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| asmi
Forum Hero
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thanks mahender.
Iappreciate your good explanation.
Can you give few points on retinoblastoma too.
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| mahendra
Forum Guru
Topics: 173
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hi asmi
these are few points on retinoblastoma RB) ANTI ONCOGENE chromosome 13
NORMAL RB protein binds to gene regulatory protein (GRP),resulting in no expression of target genes whose porducts stimulates cell cycle.thus cell cycle is SUPPRESSED.
ABNORMAL RB can not bind to GRP -EXPRESSION OF TARGET GENES THUS occurs resulting in stimulationof cell cycle-retinoblastoma.
development of retinoblastoma requires 2 seperate mutation 2 types of retinoblastoma":
Hereditary: inherit 1 mutant copy, later 2nd copy is mutated w/in many cells of retina---multiple tumors in both eyes.
NonHereditary: mutation of both copies occurs w/in 1 cell- single tumor -develops in one eye.
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| asmi
Forum Hero
Topics: 1043
Posts: 4,609
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thanks mahender 
I have got a good site if you would like to look into it..
http://0-www.nlm.nih.gov.spartan270.nsu.edu/medli...
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