Genetic Code - Lecture 39 Review

These flashcards cover key concepts related to the genetic code, tRNAs, and aminoacyl-tRNA synthetases, based on Lecture 39 notes.

What are the triplets in the genetic code?

The genetic code consists of triplets that correspond to amino acids.

What is unique about the directionality of the genetic code?

The genetic code has a 5'-to-3' directionality.

What is meant by the term 'degeneracy' in the genetic code?

Degeneracy refers to the fact that many amino acids are specified by more than one codon.

What are the stop codons in the genetic code?

The three stop codons are UAA, UAG, and UGA.

What does tRNA stand for and what is its function?

tRNA stands for transfer RNA and it is responsible for bringing amino acids to the ribosome during protein synthesis.

What does aminoacyl-tRNA synthetase do?

Aminoacyl-tRNA synthetases link amino acids to their corresponding tRNAs.

What is a key feature of tRNA structure?

tRNAs are typically L-shaped and consist of approximately 70-90 nucleotides.

Define the term 'wobble' in the context of tRNA-mRNA interactions.

Wobble refers to the ability of some tRNAs to pair with more than one codon due to flexibility in base pairing.

How are amino acids activated before they are attached to tRNA?

Amino acids are activated by reacting with ATP to form an aminoacyl adenylate.

What role does pyrophosphate play in the tRNA charging process?

Pyrophosphate is released during the formation of the aminoacyl adenylate, which helps drive the reaction forward.

Why is it important for aminoacyl-tRNA synthetases to be selective?

Selectivity ensures the correct amino acid is attached to the corresponding tRNA, preventing errors in protein synthesis.

What is co-transcriptional translation and where does it occur?

Co-transcriptional translation occurs in bacteria, where translation begins while transcription is still ongoing.

What happens to translation if ribosomes stall at tryptophan codons?

If ribosomes stall, alternative RNA secondary structures can form, preventing transcription termination.

What is the editing site in aminoacyl-tRNA synthetases used for?

The editing site is used to hydrolyze incorrectly charged tRNAs to ensure accuracy in translation.

What is the energetic cost of activating an amino acid for tRNA charging?

The net cost of activating and transferring an amino acid to tRNA is equivalent to two ATP molecules.

How does the genetic code allow for the production of insulin in bacteria?

The nearly universal nature of the genetic code enables genes from humans to be expressed in bacteria.