Summary of issues related to IT21 difficult-to-degrade DNA analysis kit

Since the introduction of the IT21 difficult-to-degrade sample DNA analysis kit, many authoritative users in China have used this reagent in the actual case to carry out typing and research, which solves the problem of classification of difficult-degraded DNA samples; The relevant questions are answered as follows:

1. Which materials does IT21 apply to?
No hair follicles dry, old bones and other low or highly degraded samples;

2. The principle of IT21?
The IT21 typing method is based on the polymorphism of Retrotransposable Elements (RE), which is a DNA sequence that plays a major role in the process of converting RNA into cDNA. It is located on the autosome and is 2 in size. 500 bp, accounting for about 40% of the autosome. It is a regulatory sequence for DNA expression, containing deleted and inserted sequences, with different sequences between each individual, and is particularly suitable for individual recognition.

3. How many samples can each kit be used to detect?
Using the recommended 25ul amplification system, 50 people can be tested;
Using 10ul amplification system commonly used in China, 100 people can be tested;

4. What are the equipment required for IT21?
IT21 does not need to purchase any additional equipment, it is suitable for the current DNA laboratory conventional platform, such as 9700/3130, 3500, 3500xl and so on.

5. What are the advantages of using the IT21 kit compared to mitochondrial sequencing?

• Simple operation and short time;
• No additional equipment support is required, suitable for routine laboratory platforms;
• Double allele analysis system, simple analysis;

6. Has it been tested by a domestic authority?
After the Ministry of Public Security, Shanghai 803, Wuhan Municipal Bureau, Beijing Dongcheng Branch and other institutions tested.

7. Why can an amplified fragment be as low as 60-125 bp?

Ultra-short primer design, the upstream primer (FC) can directly amplify the inserted or deleted site sequence, and the downstream primers are divided into two types, one is the insert primer (RI), which can be combined with the partial insertion sequence to expand Adding the insertion site sequence; the other is the deletion fragment primer (RN), which can only bind to the site without the insertion sequence; each site corresponds to three primers, so that the insertion sequence is not completely amplified, The size of the amplified product is reduced, and the success rate of amplification of highly degraded samples is increased. The details are as follows:

7. Why is the sensitivity of IT2 much higher than that of traditional STR?

The typing method of IT21 is based on the polymorphism of Retrotransposable Elements (RE). The retrotransposon plays a major role in the process of RNA conversion to cDNA. It is located on the autosome and is 2-500 bp in size. The chromosome is about 40%. The conventional STR typing is based on the polymorphism of the short tandem repeat on the autosome. The short repeat length is 100-400 bp, which is about 10% of the autosome. Therefore, the detection method of the reverse transposon polymorphism based on the "copy number" can detect lower copy DNA samples, which can be verified to be as low as 30 pg, and the theoretical sensitivity can be nearly 100 times higher than that of the conventional STR typing.

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