---
# System prepended metadata

title: '[Bioinformatics] Unique Molecular Identifiers'
tags: [TSO500, bioinformatics]

---

### Unique Molecular Identifiers (UMIs):
>  UMIs (aka “Molecular Barcodes” or “Random Barcodes”) are molecular tag consisting of a short known DNA sequence that is used to identify and quantify unique DNA molecules. This tags are added to sequencing libraries ==before any PCR amplification== steps, enabling the accurate bioinformatic identification of PCR duplicates.
> 

![](https://i.imgur.com/SJCdrU1.png)



### 用途: ==減輕PCR amplification所帶來的duplication problem.==
* 定量分析: e.g. RNA-seq, ChiP-seq

![](https://i.imgur.com/zPUwskG.png)


* 低頻率突變偵測 (cfDNA, somatic variant, etc.)

![](https://i.imgur.com/1TIBHk2.png)

### Family size and unique coverage
Family size即為具有相同barcode(同一個family)的read數，在Total read固定的情況下，Family size越大，代表unique的molecule數量越少，collpase後Unique coverage越小。

![](https://i.imgur.com/bQy6C0y.png)

### TSO500
如上述說明，TSO500採用UMI的技術後，確實降低了false positive的雜訊
![](https://i.imgur.com/GIFYRNJ.png)

![](https://i.imgur.com/xsBoICP.png)


### References:
1. https://dnatech.genomecenter.ucdavis.edu/faqs/what-are-umis-and-why-are-they-used-in-high-throughput-sequencing/
2. https://nonacus.com/blog-unique-molecular-identifiers-unmask-low-frequency-variants/
3. https://www.illumina.com/content/dam/illumina-marketing/documents/products/datasheets/trusight-oncology-umi-reagents-datasheet-1000000050425.pdf

###### tags: `genomics`