Adapter Dimer Contamination Irregularities Between Multiplexed Samples [Chip-Seq/Rna-Seq]

Question: Adapter Dimer Contamination Irregularities Between Multiplexed Samples [Chip-Seq/Rna-Seq]

6.8 years ago by

Netherlands

Sukhdeep Singh ♦ 9.7k wrote:

Hi guys,

Whenever I start working with new samples (multiplexed on HiSeq-2000), some samples house adapter-dimer contaminations and others dont. Samples are prepared by same person using same protocol, sequenced at same time in the same machine in same/different lanes, so why this difference. To my understanding the 45° Y shaped adapters are ligated to the DNA fragment, gel purified and then index + multiplex adapters are ligated which then are PCR amplified and after that ligated on to the cluster bed for bridge amplification. So, the adapters are also amplified and should present in all of them or may be I am missing something.

Thanks

Source : http://genome.med.harvard.edu/

illumina chip-seq rna-seq hiseq • 4.2k views

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modified 6 months ago by qliu • 0 • written 6.8 years ago by Sukhdeep Singh ♦ 9.7k

6.8 years ago by

Sean Davis ♦ 25k

National Institutes of Health, Bethesda, MD

Sean Davis ♦ 25k wrote:

Excessive adapter contamination can be associated with limited DNA input quantities. You may want to look at the amount of input DNA that was used to see if there is a correlation. That said, adapter contamination may or may not constitute a real problem with the data; in other words, the data may still be useable after cleaning up the contamination (often alignment will do the trick).

ADD COMMENT • link written 6.8 years ago by Sean Davis ♦ 25k

I got your point, the contamination is inversely proportional the starting material, but still all of them have adapters ligated, still some of them show it and some don't. If we have an ideal starting material, still we amplify the DNA and should observe the cotamination though less!! What do you think.

Cheers

ADD REPLY • link written 6.8 years ago by Sukhdeep Singh ♦ 9.7k

The adapters are on every sequence, but they should not be sequenced unless the insert size is small. In that case, the ends of reads will contain adapters. For that reason, there are many softwares for removing adapters from the ends of reads.

ADD REPLY • link written 6.8 years ago by Sean Davis ♦ 25k

Thanks Sean, clears things. Also, this post was helpful as well about insert size and adapters.

ADD REPLY • link written 6.8 years ago by Sukhdeep Singh ♦ 9.7k

6 months ago by

qliu • 0

qliu • 0 wrote:

Have you considered clean-up or size selection before PCR? Even though the software tools can help remove the contamination data, A proper DNA sizing or cleanup can help improve the sequencing efficiency and the data quality. Check https://www.nvigen.com/dna-size-selection-tutorial/.

ADD COMMENT • link written 6 months ago by qliu • 0

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