Genetic Code and Translation Quiz

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Questions and Answers

What role do aminoacyl-tRNA synthetases perform in protein synthesis?

They synthesize RNA from DNA templates.
They add amino acids to the growing polypeptide chain.
They catalyze the attachment of specific amino acids to their corresponding tRNA. (correct)
They regulate the initiation of transcription.

Which sequence is recognized to initiate translation in prokaryotes?

The Kozak sequence
The G-cap
The TATA box
The Shine-Dalgarno sequence (correct)

During eukaryotic translation initiation, what is the function of the G-cap?

It determines the stop codon for translation.
It signals the start of transcription.
It protects the mRNA from degradation and aids in ribosome binding. (correct)
It is the site for tRNA attachment.

Which proteins are involved in the elongation step of translation?

EF-TU, peptidyl transferase, and EF-G (B) Signup and view all the answers

What are stop codons responsible for during translation termination?

Signaling the end of translation and the release of the polypeptide chain. (D) Signup and view all the answers

What is the main reason the lac operon is only expressed under specific conditions?

Lactose is absent during glucose metabolism. (B) Signup and view all the answers

Which of the following describes a classic histone remodeling complex's role in transcription?

It alters chromatin structure to make DNA more accessible for transcription. (A) Signup and view all the answers

Which statement correctly differentiates between constitutive and regulated gene expression?

Regulated expression can respond to environmental signals, while constitutive expression is always active. (D) Signup and view all the answers

What influences the probability of a mutation being classified as cis-acting versus trans-acting?

The location of the mutation relative to the gene it influences. (C) Signup and view all the answers

What role do enhancers play in gene regulation?

They facilitate the recruitment of transcription factors and enhance the rate of transcription. (C) Signup and view all the answers

What is the primary DNA modification that regulates gene expression in eukaryotes and what effect does it typically have on transcription?

Methylation; negative effect (C) Signup and view all the answers

How does alternative splicing influence gene regulation?

It creates different mRNA transcripts from the same gene. (A) Signup and view all the answers

What is RNA interference (RNAi) and how does it affect transcription in eukaryotes?

A silencing mechanism that can downregulate gene expression. (D) Signup and view all the answers

What differentiates a missense mutation from a nonsense mutation?

Missense changes one amino acid, nonsense creates a premature stop codon. (B) Signup and view all the answers

Which type of mutation can result from spontaneous tautomerization of bases?

Substitution mutations (C) Signup and view all the answers

What is the role of proofreading by DNA polymerase?

To ensure accurate nucleotide pairing during DNA synthesis. (B) Signup and view all the answers

How does UV light cause damage to DNA, and what repair mechanism can reverse such damage?

It forms thymine dimers; nucleotide excision repair can fix it. (C) Signup and view all the answers

Which mutation type is characterized by a change in the DNA sequence that cannot revert back to the original?

Forward mutation (B) Signup and view all the answers

What are restriction endonucleases and what do they do?

Enzymes that cut DNA at specific sequences. (B) Signup and view all the answers

What barrier must be overcome when expressing mammalian genes in prokaryotic cells?

The lack of post-translational modifications in prokaryotes. (A) Signup and view all the answers

Flashcards

DNA modification for gene regulation

Methylation of DNA is a common DNA modification, affecting gene expression by influencing whether transcription occurs.

Alternative splicing effect on gene regulation

Alternative splicing creates different mRNA versions from one gene, leading to different protein products, regulating gene expression.

RNA interference (RNAi)

RNAi is a gene silencing process that reduces expression of specific mRNAs.

Point mutation types

Point mutations include transitions (purine to purine or pyrimidine to pyrimidine) and transversions (purine to pyrimidine or vice versa).