1) Which of the following statements about genetic testing methods is NOT true?
ID: 97892 • Letter: 1
Question
1) Which of the following statements about genetic testing methods is NOT true?
a. The reason that SNP-chip is the most widely used method is because it is cheap and because it tests for every possible DNA variation in the genome, as long the variation is a SNP.
b. Conventional DNA sequencing can determine the exact sequence of nucleotides for a part of the genome that is ~1000 bp in length
c. The major advantage of whole-genome sequencing is that it can identify every possible DNA variation in the genome, even variations we don’t already know about.
d. The major limitation of gel electrophoresis is that it can only be used to detect variations that differ in size.
Which of the following is the best definition of the probe used to detect a spot on the SNP chip?
a. A short piece of DNA that has been labeled with a fluorescent tag and contains nucleotides that are complementary to the strand of DNA stuck to a spot
b. Two complementary pieces of DNA annealled together to form a double-stranded molecule on the spot
c. A cyclic process of separating DNA strands on the spot, copying and re-annealing the daughter strands, and repeating this process multiple times to increase the numbers of DNA product
d. Billions of 100 base sequence reads of random fragments of a genome that a computer assembles together
a. The reason that SNP-chip is the most widely used method is because it is cheap and because it tests for every possible DNA variation in the genome, as long the variation is a SNP.
b. Conventional DNA sequencing can determine the exact sequence of nucleotides for a part of the genome that is ~1000 bp in length
c. The major advantage of whole-genome sequencing is that it can identify every possible DNA variation in the genome, even variations we don’t already know about.
d. The major limitation of gel electrophoresis is that it can only be used to detect variations that differ in size.
Explanation / Answer
Answer 1b) Conventional DNA sequencing can determine the exact sequence of nucleotides for a part of the genome that is ~1000 bp in length.
Explanation - Conventional DNA sequencing is also called as Sanger sequencing. this is the first commercialized method of sequencing which is based on dideoxy-chain termination process. the length of read (part of the genome to be sequenced) for this sequencing method can vary between 400-900bp in length, depending on the nature of DNA and need of sequencing. it is nowhere mandatory to keep the length of read at nearly 1000bp always.
Answer 2a) A short piece of DNA that has been labeled with a fluorescent tag and contains nucleotides that are complementary to the strand of DNA stuck to a spot
Explanation - Most commonly used the probe in SNP sequencing method is the molecular beacons. these are the short piece of DNA which has a complementary sequence to the both ends so that they can take a shape of hairpin/stem loop. there is fluorophore attached to its one end and the quencher at the another end. hairpin formation keeps the fluorophore and quencher together. while the loop has a complementary sequence to that of the target sequence (DNA to be analyzed). binding of the DNA to loop unwinds the hairpin structure and fluorophore and quencher gets dissociated. this wavelength of fluorescence emission is detected by the assay.
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