Eukaryotic Transcription Process

18 Questions

What is the start codon that signals the beginning of translation?

AUG

Where does the initiator tRNA sit during translation initiation?

P site

In which direction does mRNA move through the ribosome during translation?

5' end to 3' end

What happens to empty tRNAs after being released from the E site?

They return to the cytoplasm for reloading

During translation elongation, how are amino acids added to the growing chain?

Each amino acid is added individually

How is a polypeptide chain terminated during translation?

When a stop codon reaches the A site

What is the purpose of 5’ capping in mRNA processing?

Prevents degradation of mRNA by exonucleases

Which of the following enzymes is responsible for unwinding the DNA double helix during transcription elongation?

Helicase

What role does the polyadenylation signal (AAUAA) play in eukaryotic transcription termination?

Binding to RNA polymerase II to halt transcription

What is the main function of spliceosomes in pre-mRNA processing?

Removing introns and connecting exons

During elongation in transcription, what is RNA polymerase primarily responsible for?

Adding nucleotides to the growing RNA molecule

Which component specifies the site for RNA polymerase II to terminate transcription in eukaryotes?

Polyadenylation signal sequence

What is the primary function of mRNA capping in eukaryotic cells?

Preventing degradation of mRNA by exonucleases

What role do transcription factors play in the process of transcription initiation?

Mediating the binding of RNA polymerase to the promoter region

Which DNA sequence is crucial for the formation of the transcription initiation complex?

TATA box

During elongation in transcription, what is the role of RNA polymerase II?

Moving along the DNA template and synthesizing mRNA

What is the function of termination codons in the genetic code?

Signal the end of translation and release the new polypeptide chain

What is a characteristic feature of correct reading frame in translation?

Nonoverlapping three-letter words are read during reading frame

Study Notes

Transcription in Eukaryotes

Initiation: RNA polymerase II binds to the promoter, separating the DNA strands and joining RNA nucleotides complementary to the DNA.
Elongation: RNA polymerase moves along the DNA, untwisting the double helix, and adding RNA nucleotides to the 3' end of the growing RNA molecule.
Termination: RNA polymerase II transcribes the polyadenylation signal sequence (AAUAA), leading to the release of the pre-mRNA.

mRNA Processing

5' Capping: a modified guanine (G) nucleotide is added onto the 5' end of the pre-mRNA.
3' Poly-A Tail: 200 adenine residues are added to the 3' end of the pre-mRNA.
Splicing: introns are removed and exons are reconnected by spliceosomes.

Translation

Transfer RNA (tRNA): translates codons along the mRNA molecule, transferring amino acids from the cytoplasmic pool to the growing polypeptide in the ribosome.
Ribosomes: facilitate the specific coupling of tRNA anticodons with mRNA codons during protein synthesis.

The Genetic Code

64 codons: 3 termination codons, 1 initiation codon, and 61 protein-coding codons.
No ambiguity in the genetic code, but redundancy.
Correct reading frame corresponds to correct extraction of the message.

Translation Initiation

RNA polymerase II binds to the promoter, comprising specific sequences of nucleotides.
Transcription factors mediate the binding of RNA polymerase and the initiation of transcription.
Initiation complex: transcription factors and RNA polymerase II bound to the promoter.

Elongation and Termination of the Chain

Amino acids are added one by one to the previous amino acid of the growing chain.
mRNA is moved through the ribosome in one direction only, 5' end first to 3'.
Polypeptide chain is terminated when a stop codon reaches the A site.

This quiz covers the initiation, elongation, and termination stages of eukaryotic transcription. It includes information on how RNA polymerase moves along the DNA, exposes DNA nucleotides for pairing with RNA nucleotides, and adds to the growing RNA molecule. The quiz also touches on the termination process involving the polyadenylation signal sequence and protein binding.

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