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Biochemistry

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Purines, Pyrimidines and Nucleic Acid Metabolism

Question
24 out of 59
 

Subtelomeric rearrangement is detected by all except (AIIMS Nov 2010)



A FISH

B CGH array

C MLPA

D Diode dye laser

Ans. D Diode dye laser

SUBTELOMERIC REARRNGEMENTAS

Fluorescence in situ hybridization (FISH

a. In in situ hybridization, the simpler and more direct procedure, a radioactive probe is added to a metaphase spread of chromosomes on a glass slide. The exact area of hybridization is localized by layering photographic emulsion over the slide and, after exposure, lining up the grains with some histologic identification of the chromosome.

b. Fluorescence in situ hybridization (FISH)is a very sensitive technique that is also used for this purpose. This often places the gene at a location on a given band or region on the chromosome. Some of the human genes localized using these techniques are listed in Table 39–5. This table represents only a sampling, since thousands of genes have been mapped as a result of the recent sequencing of the human genome.

c. Once the defect is localized to a region of DNA that has the characteristic structure of a gene (Figure 39–1), a synthetic gene can be constructed and expressed in an appropriate vector and its function can be assessed—or the putative peptide, deduced from the open reading frame in the coding region, can be synthesized. Antibodies directed against this peptide can be used to assess whether this peptide is expressed in normal persons and whether it is absent in those with the genetic syndrome.

d. CGH Array (Comparative Genomic Hybridization Array): Also known as array-based dosage analysis, this is a newer test that uses a microchip, and can find large deletions and duplications in any exons in the dystrophin gene. Array-based testing can identify the exact beginning and end of the deleted or duplicated part of the gene. The test can find deletions/duplications in females as well as males.

e. MLPA (Multiple Ligation-dependent Probe Amplification): MLPA can find most large deletions, and many duplications, in the dystrophin gene. Sometimes duplications are difficult to detect using MLPA. Deletions found using this method sometimes have to be confirmed by a second testing method. This method can be used for carrier testing in females.

f. MAPH (Multiplex Amplifiable Probe Hybridization):This type of testing can identify most large deletions and duplications in the dystrophin gene. Deletions found using this method sometimes have to be confirmed by a second testing method. This method can be used for testing of carrier females.

Purines, Pyrimidines and Nucleic Acid Metabolism Flashcard List

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