Molecular Biology: Gene Function and Translation

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Questions and Answers

What does the 'one gene-one polypeptide' hypothesis suggest?

Each gene encodes for a single polypeptide. (correct)

Each gene encodes for multiple proteins.

Each gene encodes for a single enzyme.

Each gene is responsible for multiple traits.

Why is the genetic code described as degenerate?

Most amino acids are specified by more than one codon. (correct)

All amino acids are coded by exactly one codon.

Most codons specify more than one amino acid.

Some codons do not code for any amino acids.

What is the main role of the tRNA during translation?

To synthesize proteins directly.

To transport ribosomes to the mRNA.

To catalyze the peptide bond formation between amino acids.

To carry amino acids to the ribosome and match codons. (correct)

What distinguishes bacterial initiator tRNA from eukaryotic initiator tRNA during translation initiation?

Bacterial initiator tRNA utilizes a Shine-Dalgarno sequence. Signup and view all the answers

What occurs during the termination stage of translation?

Release factors recognize stop codons and disassemble the ribosome complex. Signup and view all the answers

Which amino acids are exceptions to the concept of the degenerate code?

Tryptophan and Methionine Signup and view all the answers

What role do elongation factors EF-Tu and EF-G play during translation?

They facilitate the addition of charged tRNA and translocation on the ribosome. Signup and view all the answers

Which statement accurately represents a key difference in initiator tRNA usage between bacteria and eukaryotes?

Eukaryotic initiator tRNA incorporates a modified form of methionine. Signup and view all the answers

What is the significance of the Wobble Hypothesis in translation?

It allows for more tRNA molecules than codons in the mRNA. Signup and view all the answers

How many nucleotide combinations are available in the genetic code, and what does this allow for?

64 combinations, accommodating all 20 amino acids. Signup and view all the answers

What is a consequence of the Wobble Hypothesis in protein synthesis?

It allows for the recognition of multiple codons by a limited number of tRNAs. Signup and view all the answers

How does the degenerate nature of the genetic code benefit organisms?

It provides redundancy, minimizing the impact of mutations. Signup and view all the answers

What is the primary role of peptidyl transferase during elongation in translation?

To catalyze the formation of peptide bonds between amino acids. Signup and view all the answers

Which statement correctly describes the initiation phase of translation in eukaryotes?

Initiation begins with the binding of mRNA to the 5' cap and poly-A tail. Signup and view all the answers

Which of the following best describes the concept of 'one gene-one enzyme' as proposed by Beadle and Tatum?

Each gene is responsible for producing a single enzyme only. Signup and view all the answers

Study Notes

Gene Function and Hypotheses

Genes are DNA segments coding for protein production.
Garrod's "inborn error of metabolism" suggested genes control enzymes.
Beadle and Tatum's "one gene-one enzyme" hypothesis broadened to "one gene-one polypeptide."

Degenerate Code and Triplet Codons

Degenerate code: Multiple codons can code for the same amino acid (except tryptophan and methionine).
Triplet codons: Three nucleotides form a codon, providing 64 combinations, sufficient for 20 amino acids.

tRNA and the Wobble Hypothesis

tRNA: Transfers amino acids to ribosomes, matching anticodons to mRNA codons.
Wobble hypothesis: Flexibility in third-base pairing reduces the number of tRNAs needed.

Translation

Initiation

Small ribosomal subunit joins mRNA and initiator tRNA.
Bacterial initiation tRNA is N-formylmethionine using Shine-Dalgarno sequence.
Eukaryotic initiation tRNA involves the 5' cap and poly-A tail.

Elongation

Charged tRNA enters the A site.
Peptide bonds form (catalyzed by peptidyl transferase).
Elongation factors (EF-Tu and EF-G) aid in tRNA addition and translocation.

Termination

Release factors recognize stop codons.
Translation ends, disassembling the ribosome complex.

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Description

This quiz covers key concepts of molecular biology, including gene function, the role of tRNA, and the process of translation. It explores important hypotheses like Garrod's and Beadle and Tatum's, along with codon usage and initiation mechanisms in protein synthesis.