IB DP Biology A1.2 Nucleic acids Exam Style Questions HL Paper 1
IB DP Biology A1.2 Nucleic acids Exam Style Questions HL Paper 1
IB DP Biology A1.2 Nucleic acids Exam Style Questions HL Paper 1 at IITian Academy focus on a specific topic or type of questions asked in actual exam. Questions are based on new syllabus for first assessment of 2025.
A1.2 Nucleic acids Topics : RNA & DNA Structure, Antiparallel, Complementarity, Directionality, Nucleosome, Hershey-Chase, Radioisotopes, Chargaff
Question
▶️Answer/Explanation
Explanation:
Watson and Crick’s model revealed DNA as a double helix with antiparallel sugar-phosphate backbones
Question
The image displays a DNA profile generated through gel electrophoresis. What might be present in each band?
A. DNA fragments with the same number of base pairs
B. Several complete DNA molecules of different lengths
C. A complete DNA molecule with a specific charge
D. One DNA strand with a particular base sequence
▶️Answer/Explanation
Answer. A. DNA fragments with the same number of base pairs
Explanation: 
In gel electrophoresis, DNA is cut into fragments using enzymes, and these fragments are placed into a gel. When an electric current is applied:
DNA fragments move through the gel smaller fragments travel farther than larger ones.
Each band represents DNA fragments of the same length, hence they have same number of base pairs.
DNA is negatively charged, hence it moves toward the positive electrode.
Question
The Human Genome Project completed the sequencing of the human genome in 2003. What could have been a source for the entire human genome?
A. The contents of a red blood cell
B. The nucleus and mitochondria of a skin cell
C. The nucleus and acrosome of a sperm cell
D. The nucleus and ribosomes of any somatic cell
▶️Answer/Explanation
Answer: B. The nucleus and mitochondria of a skin cell.
Explanation:
The human genome includes both nuclear DNA (from chromosomes) and mitochondrial DNA (mtDNA). Skin cells contain both, while red blood cells lack DNA, sperm cells have haploid nuclear DNA, and ribosomes contain no DNA
Question
Which are two proteins that assist in the unwinding and separation of DNA strands during replication?
A. Helicase and DNA polymerase III
B. DNA gyrase and DNA polymerase I
C. Helicase and DNA primase
D. Single-strand binding protein and DNA gyrase
▶️Answer/Explanation
Answer: D. Single-strand binding protein and DNA gyrase
Explanation:
Single-strand binding proteins (SSBs) prevent separated DNA strands from reannealing, while DNA gyrase relieves torsional stress during unwinding
Question
Which statement applies to tRNA?
A. There is at least one type of tRNA that combines with each known amino acid.
B. One type of tRNA can combine with all of the known amino acids.
C. tRNA carries out its main role within the nucleus.
D. tRNA is produced by the process of translation.
▶️Answer/Explanation
Ans
Answer: A. There is at least one type of tRNA that combines with each known amino acid.
Explanation:
tRNA functions as an adaptor molecule, binding specific amino acids and delivering them to ribosomes during translation. Each amino acid has at least one dedicated tRNA, ensuring accurate protein synthesis
Question
The graph shows results of an experiment by Hershey and Chase in 1952 in which bacteria were infected with a mixture of virus particles labelled with either \({ }^{32} \mathrm{P}\) or \({ }^{35} \mathrm{~S}\). A suspension of the infected bacteria was agitated with a blender, and samples collected from the suspension were centrifuged to record the percentage of isotope remaining on the outside of the cells.
What do curves X and Y represent?
▶️Answer/Explanation
Answer: B
Explanation:
Curve X represents \(^{35}\mathrm{S}\)-protein(declining as it enters bacteria), while Y represents \(^{32}\mathrm{P}\)-DNA (stable as it remains outside). This confirmed DNA, not protein, is the genetic material.