Molecular Genetics and Gene Expression Quiz

Grade 12 · Science · Quiz

Test your knowledge of transcription, translation, gene regulation, and the central dogma.

Questions

1. Which RNA molecule carries an amino acid to the ribosome during translation?

   1. mRNA
   2. rRNA
   3. tRNA
   4. snRNA
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   Answer: tRNA

   Transfer RNA (tRNA) carries specific amino acids and has an anticodon that pairs with the mRNA codon at the ribosome during translation.

2. In eukaryotes, transcription and translation occur simultaneously in the cytoplasm.

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   Answer: False

   In eukaryotes, transcription occurs in the nucleus and translation in the cytoplasm — they are spatially separated. In prokaryotes (no nucleus), they can occur simultaneously.

3. The promoter region of a gene is where ___ binds to initiate transcription.

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   Answer: RNA polymerase

   RNA polymerase recognizes and binds to the promoter region to begin unwinding DNA and synthesizing the mRNA strand.

4. How many codons in the standard genetic code are stop codons?

   1. 1
   2. 2
   3. 3
   4. 4
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   Answer: 3

   Three stop codons exist: UAA, UAG, and UGA. They signal termination of translation without coding for any amino acid.

5. A missense mutation changes one amino acid to a different amino acid.

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   Answer: True

   A missense mutation is a point mutation where one nucleotide change causes a different amino acid to be incorporated, potentially altering protein function.

6. What process removes introns from pre-mRNA?

   1. Replication
   2. RNA splicing
   3. Translation
   4. Transcription
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   Answer: RNA splicing

   RNA splicing removes introns and joins exons in the pre-mRNA. This is carried out by the spliceosome complex in eukaryotic nuclei.

7. The start codon AUG codes for the amino acid ___.

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   Answer: methionine

   AUG is the universal start codon and also codes for the amino acid methionine. All eukaryotic proteins begin synthesis with methionine.

8. A nonsense mutation introduces a premature stop codon into the mRNA.

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   Answer: True

   A nonsense mutation converts an amino acid codon into a stop codon, truncating the protein prematurely and usually causing loss of function.

9. In the lac operon, the repressor protein binds to the ___ to block transcription.

   1. Promoter
   2. Operator
   3. Structural gene
   4. Ribosome binding site
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   Answer: Operator

   In the lac operon, the repressor protein binds the operator (a DNA sequence between promoter and structural genes) to physically block RNA polymerase.

10. Which of the following best describes epigenetic modification?

    1. A change in the DNA nucleotide sequence
    2. A change in gene expression without altering DNA sequence
    3. Mutation caused by radiation
    4. Deletion of a chromosome segment
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    Answer: A change in gene expression without altering DNA sequence

    Epigenetics involves changes like DNA methylation or histone modification that alter gene activity without changing the underlying nucleotide sequence.

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