ROLL NO.17

SEM-4

GOVT. SCIENCE COLLEGE

XENOBIOLOGY • Xeno- strange or guest

• Biology – study of life

• So xenobiology is a study of strange form of life

What is xenobiology?

DEFINITION

• Xenobiology (XB) is a subfield of synthetic biology, the study of synthesizing and manipulating biological devices and systems. Xenobiology derives from the term xenos (Greek)and means "stranger or guest". So XB describes a form of biology that is not (yet) familiar to science and is not found in nature

INTRODUCTION

The genetic code of all living organisms does not know more than eight nucleoside triphosphates, four in RNA and four in DNA

Synthetic biologists have now altered these canonical nucleotides to the effect that natural biological organisms and systems cannot read and interpret them any more

Normal genome We know four

alphabets!

Well then also u cannot

read me!!Lol!!

Synthetic genome

• Experiments replacing or enlarging the genetic alphabet of DNA with unnatural base pairs led for example to a genetic code that instead of four bases ATGC had six bases ATGCPZ

• 60 candidate bases (that means 3,600 base pairs) were tested for possible incorporation in the DNA

Example ,At least on one occasion a modified variant of the HIV-reverse transcriptase was found to be able to PCR-amplify an oligonucleotidecontaining a third type base pair.

Only two amino acids were substituted in the natural polymerase optimized for the four standard nucleotides to create one that supports repeated PCR cycles for the amplification of an expanded genetic system.

XNA

Backbone of dna contain five carbon containing ring that is pentose while the Xna backbone contain as threose, glycol, hexitol etc.

Such as-

TNA (THEROSE NUCLIC ACID)

GNA (GLYCO NUCLIC ACID)

HNA (hexitol NUCLIC ACID)

• Tna- is an artificial genetic polymer invented by Albert Eschenmoser. TNA has a backbone structure composed of repeating threose sugars linked together by phosphodiester bonds. Like DNA and RNA, TNA can store genetic information in strings of nucleotide sequences

• Gna- is an artificial genetic polymer compose of repeating units of glycol linked with phosphodiester bonds. Like dna and rna , gna can also store genetic information in a string of nucleotide sequence

• HNA- hexitol nucleic acid an artificial polymer compose of repenting units of 6 carbon containing monosaccharide linked together by phosphodiester bond

• The authors picked five in total, all with features that were distinct from the normal sugars, like a double bond between carbon atoms, a fluorine replacing an oxygen, and a double-ring structure. Collectively, they termed these DNA/RNA substitutes XNAs.

• Although the genetic information is still stored in the four canonical base pairs, natural DNA polymerases cannot read and duplicate this information. In other words the genetic information stored in XNA is “invisible” and therefore useless to natural DNA-based organisms

• Using their lab-made XNAs as building blocks, the team were able to create synthetic enzymes, which they have named ‘XNAzymes’, that could cut up and stitch together small chunks of genetic material, just like naturally occurring enzymes

Example ,At least on one occasion a modified variant of the HIV-reverse transcriptase was found to be able to PCR-amplify an oligonucleotide containing a third type base pair.

Only two amino acids were substituted in the natural polymerase optimized for the four standard nucleotides to create one that supports repeated PCR cycles for the amplification of an expanded genetic system.

APPLICATION

MEDICINESMedicine, too, could benefit from XNAs, Romesberg says. Doctors already prescribe biological products such as enzymes and antibodies to treat certain diseases, but these drugs break down quickly in the stomach and the blood stream. Because XNAs are somewhat foreign, they're not broken down as quickly in the body, as it has not evolved enzymes to digest them.

main opportunities

Better understanding of the origin of life

More efficient industrial

biotechnology production systems

A solution to the upcoming biosafety

challenges

Why was this basic chemical make-up evolutionarily successful while others were not?

Industrial strains with a

fundamentally different genetic code would suddenly be immune to natural phages or viruses.

genetic firewall

CONCLUSION

REFERENCE

• http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2909387/

• https://books.google.co.in/books?id=nbuKezXzmZUC&pg=PA326&lpg=PA326&dq=ATGCPZ&source=bl&ots=uxbh_alk0u&sig=INZc9fAjVu95dY_N8U4CpmpPrEE&hl=en&sa=X&ei=7iDXVKuzDcSMuATu94DQCw&ved=0CCIQ6AEwAA#v=onepage&q=ATGCPZ&f=false

• http://www.dailymail.co.uk/sciencetech/article-2857172/Do-need-DNA-form-life-Breakthrough-synthetic-enzymes-lead-manufacture-organisms.html

• http://www.popularmechanics.com/science/health/a7636/xna-synthetic-dna-that-can-evolve-8210483/