IB Diploma · Biology D1.2
IB Biology D1.2: Protein Syn. — Practice Questions & Answers
IB Biology D1.2 protein synthesis study notes: transcription, translation, the genetic code, codons and anticodons, and ribosomes and tRNA.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
Which of the following statements accurately describe "transcription" in molecular biology?
- I. It is the process by which a cell synthesizes an RNA molecule using a DNA template
- IV. The enzyme primarily responsible for carrying out this process is RNA polymerase
- III. It is the first step in gene expression, leading to the production of proteins or functional RNA molecules
- II. It involves the synthesis of a protein molecule from an mRNA template on ribosomes
- I, III and IV only
- All I, II, III and IV
- I and II only
- I, II and III only
- III and IV only
- II, III and IV only
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WhyTranscription copies a DNA gene into mRNA using RNA polymerase and complementary base pairing.
2
Multiple choice
What enzyme plays a key role in transcription?
- RNA polymerase.
- DNA polymerase.
- Helicase.
- Ligase.
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WhyRNA polymerase synthesises RNA by joining nucleotides complementary to the DNA template strand.
3
Multiple choice
Which types of bonding are crucial for the process of transcription?
- I. Hydrogen bonds between the DNA template strand and the incoming complementary RNA nucleotides.
- II. Phosphodiester bonds formed between the nucleotides of the newly synthesized RNA molecule.
- III. Peptide bonds that link amino acids together to form the RNA polymerase enzyme itself.
- IV. Ionic bonds that form the stable double helix structure of the DNA template permanently throughout the process.
- I, II, and III only
- I and II only
- All I, II, III, and IV
- II and III only
- II, III, and IV only
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WhyTranscription relies on hydrogen bonds, phosphodiester bonds, and covalent bonds forming the RNA strand.
4
Multiple choice
What is the complementary base pairing during transcription?
- Adenine (A) on DNA pairs with uracil (U) on RNA.
- Adenine (A) on DNA pairs with thymine (T) on RNA.
- Guanine (G) on DNA pairs with uracil (U) on RNA.
- Cytosine (C) on DNA pairs with thymine (T) on RNA.
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WhyDuring transcription adenine on the DNA template pairs with uracil in the newly made RNA.
5
Multiple choice
Which of the following factors contribute significantly to the remarkable stability of DNA templates?
- I. The presence of strong covalent phosphodiester bonds forming the sugar-phosphate backbone of each DNA strand.
- II. Numerous hydrogen bonds between complementary base pairs (A-T and G-C) along the length of the double helix.
- III. The presence of a highly reactive 2'-hydroxyl group on each deoxyribose sugar, which makes it resistant to degradation.
- I and II only
- All I, II and III
- II and III only
- I and III only
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WhyThe double helix and complementary base pairing give DNA templates the stability needed for repeated transcription.
6
Multiple choice
What is the significance of transcription in gene expression?
- It is the first step in expressing a gene and can be regulated
- It is the final step in protein synthesis
- It occurs only during DNA replication
- It involves DNA polymerase
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WhyTranscription is the first, regulated step of gene expression, producing the mRNA that codes for a protein.
7
Multiple choice
What is translation?
- The synthesis of polypeptides from mRNA.
- The synthesis of RNA from DNA.
- The replication of DNA.
- The breakdown of proteins.
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WhyTranslation is the ribosomal synthesis of polypeptides using the codon sequence carried by mRNA.
8
Multiple choice
Which of the following are key molecules directly involved in the process of translation (protein synthesis)?
- II. Messenger RNA (mRNA), which carries the genetic code from DNA.
- IV. Transfer RNA (tRNA), which carries specific amino acids to the ribosome.
- I. Ribosomes, which are composed of ribosomal RNA (rRNA) and proteins, and serve as the site of protein synthesis.
- III. DNA polymerase, which is responsible for replicating DNA.
- I, II and IV only
- I and IV only
- I, II, and III only
- II, III, and IV only
- All I, II, III and IV
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WhyTranslation directly involves mRNA, tRNA, and ribosomes working together to build the polypeptide.
9
Multiple choice
Where does mRNA bind during translation?
- The small subunit of the ribosome.
- The large subunit of the ribosome.
- The nucleus.
- The cytoplasm.
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WhymRNA binds to the small subunit of the ribosome at the start of translation.
10
Multiple choice
How many tRNAs can bind simultaneously to the large subunit of a ribosome?
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WhyTwo tRNAs occupy the ribosome's large subunit at once, allowing a peptide bond to form between their amino acids.
Key terms in Protein Syn.
Transcription: The synthesis of messenger RNA from a DNA template strand, carried out by RNA polymerase.
Translation: The synthesis of a polypeptide at a ribosome using the codon sequence of mRNA.
Messenger RNA (mRNA): A single-stranded RNA copy of a gene that carries the coded message from the nucleus to a ribosome.
RNA polymerase: The enzyme that builds mRNA by adding complementary RNA nucleotides to a DNA template.
Codon: A sequence of three bases in mRNA that specifies one amino acid or a start or stop signal.
Anticodon: A sequence of three bases on a tRNA molecule that pairs with a complementary mRNA codon.
Transfer RNA (tRNA): An RNA molecule that carries a specific amino acid to the ribosome and matches it to a codon via its anticodon.
Ribosome: The structure that holds mRNA and tRNAs in place and catalyses peptide bond formation during translation.
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