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#5' to 3' direction

3 public questions tagged with this topic.

Translation in Prokaryotes and Eukaryotes

During elongation, ribosome moves in direction

Genetic information decoding demands that ribosomes traverse messenger RNA from 5' end toward 3' end, reading codons sequentially while synthesizing polypeptide amino to carboxyl directionally. During each elongation cycle, EF-G or eEF2 catalyzes translocation that advances the ribosome by three nucleotides in the 5' to 3' direction along mRNA, repositioning peptidyl-tRNA from A to P site and deacylated tRNA from P to E site, thereby exposing the next codon in A site for decoding. Reverse 3' to 5' movement, random walk, or bidirectional sliding would disrupt reading frame maintenance and cause

Ref: Lodish Molecular Cell Biology Fig 4-30; Alberts - ribosome moves 5'->3' on mRNA during elongation to preserve reading frame

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Transcription Basics

RNA synthesis during transcription occurs in which direction?

Chain growth polarity dictated by chemistry of polymerase active site containing two magnesium ions. Nucleophilic attack by 3' hydroxyl of nascent RNA on alpha phosphate of incoming nucleoside triphosphate extends chain toward distal 5' to 3' direction. Polymerase simultaneously translocates downstream along antiparallel template reading 3' to 5', preserving RNA-DNA hybrid of eight to nine bases. Because synthesis requires free 3' OH, direction fixed unidirectionally analogous to DNA polymerases. This polarity ensures nascent RNA emerges 5' end first from exit channel while template entry dete

Ref: Berg Biochemistry 9th ed. Chapter 28: RNA synthesis 5' to 3' direction mechanism; Watson Chapter 13 Polarity

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Replication Basics

DNA synthesis occurs in which direction?

DNA polymerase active site structurally restricts addition to 3' terminus, moving along template 3' to 5' while synthesizing new strand 5' to 3' opposite direction. Nucleotide triphosphate binds with sugar oriented allowing hydroxyl attack; incoming base pairing verified before catalysis. Because template is read opposite, double helix grows antiparallel, semidiscontinuous leading to continuous leading strand advancing with fork and discontinuous lagging strand via Okazaki fragments. Directionality ensures high-fidelity Watson-Crick pairing and couples polymerization to pyrophosphate release d

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: DNA Synthesis Occurs in 5' to 3' Direction

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