Kavita Maurya (MT15032) Meetika Anand (MT15033)

OUTLINE Introduction About DNA Why we are preferring DNA as an information storage device? How information is stored in DNA? Coding System Disadvantages Conclusion

INTRODUCTION  Human-beings have always been fond of accessing more and more information in minimum possible time and space. Consequently New Generation Computers and High Speed Internet have gained popularity in the recent years.  We have been witness to remarkable achievements like the transition from the bulky hard-drives to the flash drives which has made personal data storage efficiently manageable.  But when it comes to handling big data, the data of a corporation or of the world as a whole, the present data storage technology comes nowhere near to be able to manage it efficiently.  An urgent need for a proper medium for information archival and retrieval purposes arises.

Innovative Substitute - DNA  Stability: DNA is a very stable molecule, especially if it is stored in cold, dry, and dark conditions. Woolly mammoth DNA has been found in colder regions that has been preserved for thousands of years.  Density: One gram of DNA can store 700 terabytes of data To store 700TB on hard drives, you’d need 233 3TB drives, weighing a total of 151 kilos. It is theoretically possible to "store at least 100 million hours of high-definition video in about a cup of DNA.“  Long Shelf Life: DNA is a very robust material and has a very long shelf life with no attenuation in data.  Similar Coding Scheme: Coding language of nature is very similar to the binary language we use in computers

ABOUT DNA DNA stands for Deoxyribonucleic acid. DNA molecules are double-stranded helices. It is composed of two strands, which run in opposite directions. The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T) The backbone is based on a sugar-phosphate molecule Actual coding sequence is based on four nitrogenous bases which are hydrogen bonded together, keeping the strands coiled. A pairs with T and C pairs with G

ENCODING SCHEME 1 In this encoding, Quaternary number system is used. Thus, 2 bits are stored per nucleotide  First we should use numbers to represent the letters in ASCII code From ASCII table V=86 V=86 I=73 T=84  Then change to quaternary numbers 86= = = = 1110  Use “A,T, C & G” to represent the numbers 0 = A 1 = T 2 = C 3 = G VVIT would be encoded as TTTCTTTCTACTTTTA Encoding Table DNA sequence Compression Quaternary number system

ENCODING SCHEME 2 In this encoding scheme,  1 bit is stored per nucleotide  A or C is set as 0 and T or G is set as 1. This was due to the fact that a sequence like AAACTGG read in one direction (say 5’-3’) would give the same result as that of CCAGTTT read in reverse ( 3’-5’ direction). In the helical structure of DNA, AT has 2 hydrogen bonds and CG has 3 hydrogen bonds. More CG content increases its thermal stability. But too much CG content can result in formation of secondary structure like hairpin loops, and increases melting point. It also affects the longevity of the cell. Therefore reading these structure becomes difficult and expensive. This encoding scheme facilitates us to control CG content in our DNA

Cost : The production costs of generating raw, unassembled sequence (reading) data is high. Synthesizing artificial sequences is costlier. Speed: Speed is low. The fastest current technology can sequence (read) DNA on the order of about 1 billion bases per hour. Synthesis (write) is even slower and more expensive as well. This is extremely slow compared to modern storage media but would be suitable for long term data storage. Rewriting: This is essentially a write-once technology, but static data like government and historical records could benefit from this storage option.

Conclusion The longer you want to store information, then, the more attractive DNA becomes. And the cost of sequencing and synthesizing DNA is falling fast., "There's no problem with holding a lot of information in DNA”, "The problem is paying for doing that“. We can't get obsessed with the fact that it may not be practical today. If we do any reasonable projection of current trends 5 or 10 years into the future you see that this is in the sweet spot.

Natural selection and evolution have used DNA to store and read out to make our bodies and we are now using DNA to store and archive the products of our brains……. what a twist!