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📝 Transcription and translation protein synthesis (7 MCQs)

📖 From Campbell Biology • 1. Evolution and the theme of Biology and Scientific Inquiry • 7 questions available

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What is Transcription and translation protein synthesis?

Definition:
Transcription and translation are two major stages involved in protein synthesis. Transcription uses DNA information to produce an RNA molecule, while translation uses the information in $mRNA$ to assemble amino acids into a specific protein sequence.

Working:
During transcription, RNA polymerase produces an RNA copy from a DNA template. During translation, ribosomes read $mRNA$ codons and connect amino acids in the corresponding order.

Example:
If an $mRNA$ sequence contains $AUG-GGC$ , the ribosome interprets the codons to begin assembling a protein with methionine followed by glycine.

Reason:
These processes allow genetic information stored in DNA to be converted into functional proteins that contribute to cell structure and activity.

Easy

Medium

Hard

📝 All Transcription and translation protein synthesis MCQs

Q1. A researcher observes that a DNA segment contains the information needed to produce a protein. Which sequence of cellular events best represents the flow of information?

A.DNA is translated directly into protein, then RNA is produced

B.DNA is transcribed into RNA, and the RNA is translated into protein ✅

C.RNA is translated into DNA, and DNA is transcribed into protein

D.Protein is transcribed into RNA, and RNA is translated into DNA

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Transcription copies information from DNA into an RNA molecule, while translation uses the RNA sequence to determine the amino acid sequence of a protein. This separation allows genetic information to be expressed through an intermediate RNA molecule.

Q2. A mutation changes one DNA nucleotide, but the resulting mRNA and protein are unchanged. Which explanation best accounts for this observation?

A.Every DNA mutation is repaired before transcription

B.The altered nucleotide may not change the encoded amino acid ✅

C.Translation can occur without reading mRNA

D.mRNA always contains a completely different sequence from DNA

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: A nucleotide substitution can leave the protein unchanged when the altered codon still specifies the same amino acid. Therefore, a change in DNA does not necessarily produce a detectable change in the final protein.

Q3. A cell produces normal amounts of mRNA for a gene, but almost no functional protein is detected. The mRNA sequence is confirmed to be correct. Which additional defect would most directly explain the result?

A.Failure of ribosomes to properly translate the mRNA ✅

B.Failure of DNA to replicate before transcription

C.Increased production of unrelated mRNA molecules

D.Replacement of RNA nucleotides with DNA nucleotides during transcription

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: If correctly formed mRNA is present but functional protein is absent, the problem is likely downstream of transcription. A defect in ribosome function or another translation component could prevent the mRNA from being accurately converted into protein.

Q4. A student claims, Because DNA contains the information for a protein, ribosomes should read DNA directly to assemble amino acids." What is the main error in this reasoning?"

A.Ribosomes do not participate in protein synthesis

B.DNA contains no genetic information

C.Ribosomes use RNA as the template during translation rather than directly reading DNA ✅

D.Amino acids are produced only during DNA replication

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: The reasoning incorrectly connects DNA directly to ribosomal translation. DNA is first transcribed into RNA, and the resulting RNA provides the sequence information that ribosomes interpret during protein synthesis.

Q5. In an experiment, protein production is measured as the amount of newly synthesized protein over time after a gene is activated. The measured values are 0 units at 0 minutes, 5 units at 10 minutes, 15 units at 20 minutes, and 30 units at 30 minutes. Which conclusion is best supported by these observations?

A.Protein production decreases continuously after activation

B.Protein production increases over time, suggesting increasing expression of the gene ✅

C.Translation must stop completely after 20 minutes

D.The data prove that DNA replication is occurring faster than transcription

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The measurements show a continuous increase in newly synthesized protein from 0 to 30 minutes. This pattern supports increasing gene expression, although it does not by itself establish whether transcription, translation, or both are changing.

Q6. Two cells contain the same gene. Cell X produces abundant mRNA but little protein, whereas Cell Y produces moderate amounts of mRNA and abundant protein. Which interpretation best explains the comparison?

A.Cell X necessarily has more DNA than Cell Y

B.Cell Y may translate its available mRNA more efficiently than Cell X ✅

C.Cell X cannot perform transcription

D.Cell Y must have converted protein back into DNA

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The comparison demonstrates that mRNA abundance alone does not determine protein output. Cell Y could have more efficient translation, greater ribosome availability, or better mRNA stability, allowing moderate mRNA levels to generate substantial protein.

Q7. A coding sequence contains three consecutive codons. A single nucleotide insertion occurs near the beginning of the sequence, shifting how subsequent bases are grouped into codons. Why could this mutation have a much larger effect than a single nucleotide substitution?

A.An insertion can alter the reading frame and change many downstream codons ✅

B.A substitution always changes every amino acid in the protein

C.Insertions cannot occur in DNA

D.The ribosome ignores all nucleotides after an insertion

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: A single nucleotide insertion can shift the reading frame, causing downstream nucleotides to be interpreted in different three-base groups. Consequently, many subsequent amino acids may change, potentially producing a severely altered or nonfunctional protein.

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