Chapter 19, Problem 1TYK

Summary Introduction

Introduction:

The process of determining the sequence of nucleic acid is known as DNA (deoxyribonucleic acid) sequencing. There are several methods to sequence the DNA such as the Sanger method, which is also known as the dideoxy sequencing, and modern third generation methods such as Solexa/Illumina DNA sequencing method.

Answer to Problem 1TYK

Correct answer:

The sequencing of DNA fragments is more at the same time.

Explanation of Solution

Explanation for the correct answer:

Option (b) states that the Illumina DNA sequencing method sequences more DNA fragments at the same time. The Illumina method is the NGS (next-generation sequencing) technique. This technique involves the sequencing of DNA by tracking the nucleotides that are labeled as the copies of DNA. This takes place in a parallel fashion. The data output in illumina method is up to 300 kb (kilobases) to several tb (terabases) just in a single run as compared to Sanger method, which requires large amount of DNA for each read. Hence, option (b) is correct.

Explanation for the incorrect answer:

Option (a) states that the sequencing of longer fragments of DNA takes place in the Illumina DNA sequencing method. The DNA fragments are cut short during the sequencing of DNA using the Illumina method. These short double-stranded adapter molecules are attached to the end of the DNA fragments with the help of an enzyme known as DNA ligase. So, it is an incorrect option.

Option (c) states that the fluorescent markers are not required. Illumina sequencing of DNA involves the addition of primer to the cell. This primer attaches to each DNA strand and then DNA is synthesized. The synthesis of each DNA strand is done with the help of four different fluorescent labels put on the DNA nucleotide progenitor. So, it is an incorrect option.

Option (d) is states that the amplification of DNA is not done before sequencing. DNA strands form a cluster of multiple copies of DNA during the sequencing by the Illumina DNA sequencing method that is single-stranded. This single-stranded DNA undergoes the process of amplification. So, it is an incorrect option.

Option (e) states that the computer algorithms are not required to look for places where overlapping of sequencing takes place. The fluorescent tagging on nucleotides enables computer to analyze the kind of base that was added with the help of the wavelength. The computer remembers it for every spot and the molecules that are not corporated are removed. So, it is an incorrect option.

Hence, options (a), (c), (d), and (e) are incorrect.

Conclusion

Therefore, it may be concluded that the Illumina DNA sequencing method is faster as it only requires a single strand of DNA while Sanger method requires multiple copies of DNA. The Illumina DNA sequencing method can sequence a number of DNA fragments at the same time.