Question

Contrast the type of signal that is used to detect a growing DNA strand in Illumina vs. 454 sequencing.

Answer 1

Answer :

454 sequencing can sequence much longer reads than illumina.

454 sequencing does this by multiple reads at once by reading optical signals as bases are added.

454 sequencing in mych cheaper and faster.

As in illumina the DNA or RNA is fragmented into shorter reads but upto 1kb.

Illumina sequencing is a four colour sequencing by synthesis approach where incorporation of a reversible terminator nucleotide generates a fluorescent signal detected by a high sensitive camera. For A C G T during each cycle.

In 454 sequencing addition of one nucleotide generates a light signal that is read by ccd camera in the instrument. Signal strength is proportional to the number of nucleotides. However the the signal strength for homopolymer stretches were linear only upto 8 consecutive nucleotides. After which signal fell off rapidly.