Evolucija genetskog koda

undergraduate thesis

• Title (english): Evolution of the genetic code
• Author: Borna Branimir Vuković
• Mentor: Jasmina Rokov Plavec (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Granter: University of Zagreb; Faculty of Science; (Department of Chemistry); Zagreb
• Defense date and country: 2021-09-23, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Standardni genetski kod – informacija u obliku 64 tripleta dušičnih baza (kodona) na mRNA koji kodiraju 20 proteinogenih aminokiselina, gotovo je univerzalan, uz ograničene iznimke, u svim organizmima na Zemlji i otporan na štetne učinke mutacija u sekvenci kodona. Pokušavajući objasniti evoluciju navedenih svojstava razvijene su 4 hipoteze. Hipoteza zamrznute slučajnosti tvrdi da su aminokiseline nasumično povezane s pripadajućim kodonima te da je univerzalnost koda rezultat štetnih učinaka potencijalnih promjena. Stereokemijska hipoteza objašnjava povezanost aminokiselina s pripadajućim kodonima ili antikodonima putem direktnih stereokemijskih interakcija. Koevolucijska hipoteza tvrdi da su rane aminokiseline uklopljene u kod iz abiotskih prekursora, a kasne usporedno s evolucijom njihovih biosintetskih puteva. Hipoteza umanjivanja grešaka predlaže da je glavni selekcijski pritisak evolucije koda bio prema većoj otpornosti na učinke mutacija, no novija istraživanja potvrđuju da je otpornost koda najvjerojatnije nusprodukt drugih selekcijskih pritisaka. Eksperimenti koji povezuju ideje četiriju hipoteza s evolucijom translacijske mašinerije nude najbolje mogućnosti rekonstrukcije evolucijskog puta genetskog koda, s obzirom da je svaka od hipoteza pojedinačno u tome neuspješna. Genetski kod se danas nalazi u novoj, in vitro evolucijskoj fazi zahvaljujući razvoju nestandardnih aminokiselina i sintetskih baza. Razumijevanje prošlosti genetskog koda, odnosno principa njegove evolucije, važno je za ostvarivanje napretka u novoj evolucijskoj fazi.

Abstract (english)

The standard genetic code – the information stored in 64 triplets of nitrogenous bases (codons) in mRNA, which encode 20 proteinogenic amino acids, is nearly universal, with limited exceptions, in all life forms on Earth and it exhibits robustness to harmful effects of mutations in codon sequence. Four hypotheses were put forward in an effort to explain those properties. The frozen accident hypothesis posits that amino acids were coincidentally connected with cognate codons and that the code’s universality is the result of harmful effects of potential alterations. The stereochemical hypothesis explains the connection of amino acids and cognate codons or anticodons by direct stereochemical interactions. The coevolution hypothesis claims that early amino acids were incorporated into the code from abiotic precursors, and the incorporation of late amino acids was concurrent with the evolution of their respective biosynthetic pathways. Error minimization hypothesis proposes that the main selective pressure of code evolution was to obtain greater robustness to effects of mutations, but more recent experiments confirmed that the code’s robustness is most likely a by-product of other selective pressures. Experiments integrating the ideas of the 4 hypotheses with the evolution of the translational apparatus put forward the best possibility of reconstructing the code’s evolutionary path, since none of the hypotheses individually is able to do so. The genetic code today is in a new, in vitro evolutionary stage owing to the development of nonstandard amino acids and synthetic bases. Understanding the code’s past, that is the principles of its evolution, is important in order to accomplish progress in its new evolutionary stage.

• Keywords: standardni genetski kod; evolucija; zamrznuta slučajnost; rane i kasne aminokiseline; stereokemija; kolevolucija; umanjivanje grešaka; translacija; aminoacil-tRNA-sintetaze
• Keywords (english): standard genetic code; evolution; frozen accident; early and late amino acids; stereochemistry; coevolution; error minimization; translation; aminoacyl-tRNA synthetases
• Language: croatian
• URN:NBN: urn:nbn:hr:217:034679
• Study programme: Title: Molecular Biology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-09-28 12:35:50