Describe synthetic biology and engineered pathways

6.3.13 · Biology › Biotechnology Applications

WHAT is Synthetic Biology?

Key vocabulary jo tumhe pakki karni hai:

WHY do it? (The 80/20 core)

Woh 20% jo 80% marks deta hai:

1. Standardized parts (promoter + coding sequence + terminator/poly(A) = ek "cassette").
2. Chassis parts ko host karta hai.
3. Pathways kisi substrate ka flux redirect karti hain ek target product ki taraf.
4. Real example: yeast mein artemisinic acid; E. coli mein insulin.

HOW is a pathway built? (Derivation from first principles)

Logic ko scratch se build karte hain, memorize nahi karte.

Step 1 — Ek gene ko express hona chahiye enzyme banana ke liye. Kyun? Kyunki sirf transcribed + translated DNA ek working enzyme banta hai. Isliye minimal unit — expression cassette — parts ka woh set hai jo (a) transcription shuru kare, (b) ribosome ko translation shuru karne de, (c) protein encode kare, aur (d) transcription rok de. Exact parts chassis par depend karte hain:

$\underset{\text{Prokaryote (e.g. }E.coli\text{)}}{\underbrace{\text{Promoter}\to \text{RBS}\to \text{CDS}\to \text{Terminator}}}$

$\underset{\text{Eukaryote (e.g. yeast)}}{\underbrace{\text{Promoter}\to {\text{5}}^{\prime }\text{-UTR/Kozak}\to \text{CDS}\to \text{poly(A) signal}}}$

Difference kyun hai? Bacteria mein ribosome mRNA ko ek Shine–Dalgarno / RBS sequence ke zariye dhundhta hai, aur transcription ek simple terminator par khatam hoti hai. Eukaryotes mein translation cap se 5′-UTR / Kozak sequence ke through scanning karke shuru hoti hai, aur transcript ko stable, exportable mRNA ke liye polyadenylated hona padta hai (ek poly(A) signal cleavage + tail addition direct karta hai) — wahan bacterial RBS/terminator kaam nahi karega. Same logic (start–translate–stop), alag molecular parts.

Step 2 — Ek enzyme ek conversion karti hai. Enzyme $E_1$ substrate $S\to A$ convert karti hai. Ek door product tak pahunchne ke liye humein ek chain chahiye:

$S\stackrel{E_1}{\to }A\stackrel{E_2}{\to }B\stackrel{E_3}{\to }P$

Chain kyun? Kyunki koi bhi single enzyme $S$ se $P$ tak seedha jump nahi karti; har step ek small chemical change hai jo ek specific enzyme catalyse karti hai. Isliye hum $E_1,E_2,E_3$ ke cassettes insert karte hain.

Step 3 — Flux balance karo. Agar $E_2$ slow hai, toh intermediate $A$ pile up hoga (shayad toxic) aur $P$ output girega. Isliye hum promoter strength tune karte hain "conveyor belt" balance karne ke liye. Yahi woh engineering insight hai jo nature ne kabhi hamare product ke liye optimise nahi ki.

Worked Examples

Common Mistakes (Steel-manned)

Flashcards

Connections

• Recombinant DNA Technology — woh tools (restriction enzymes, plasmids) jo part-insertion possible banate hain
• Gene Expression and Regulation — isliye promoters, RBS/Kozak aur poly(A) signals output control karte hain
• Metabolic Pathways — woh natural enzyme chains jo hum hijack ya extend karte hain
• Fermentation and Bioreactors — engineered chassis ko industrially scale up kaise karte hain
• Insulin Production aur Genetically Modified Organisms — flagship applications
• Protein Folding and Post-translational Modification — isliye disulfide bonds aur cleavage insulin finish karte hain
• Enzymes and Catalysis — pathway ka har step enzyme-catalysed hota hai

Concept Map