Home / IB DP Biology- A1.2 Nucleic acids – IB Style Questions For HL Paper 1A

IB DP Biology- A1.2 Nucleic acids - IB Style Questions For HL Paper 1A -New Syllabus

IBDP Biology HL Paper 1 -FA 2025- All Chapters

Question

The diagram shows a structural component found inside a eukaryotic nucleus.

What do the labels X and Y represent?

XY
RibosomemRNA
HistoneLinker DNA
NucleosomemRNA
RNA polymeraseLinker DNA
▶️ Answer/Explanation
The diagram shows DNA wrapped around histone proteins to form nucleosomes. X represents the histone core, and Y represents the linker DNA connecting nucleosomes.
✅ Answer: (B)

Question

Hershey and Chase used bacteriophages to investigate the chemical nature of genes. The phosphorus in the DNA and the sulphur in the protein coat of the bacteriophages were labelled with radioactive isotopes.

Hershey and Chase Experiment

After the bacteriophages infected bacterial cells, the mixture was centrifuged. The following observations were recorded.

Sample sourceSupernatantPellet
Concentration of radioactive sulphur (35S)HighLow
Concentration of radioactive phosphorus (32P)LowHigh

What did Hershey and Chase conclude from their experiment?

(A) Viral DNA was found within the bacterial cells.
(B) Viruses infect bacterial cells with proteins.
(C) DNA was mainly outside the bacterial cells.
(D) Neither protein nor DNA were chemicals making up genes in viruses.
▶️ Answer/Explanation

Correct Answer: \( \boxed{\mathbf{A}} \)

The radioactive phosphorus (32P) was detected in the pellet, showing that viral DNA entered the bacterial cells. The radioactive sulphur (35S) remained mainly in the supernatant, indicating that the protein coat stayed outside. This demonstrated that DNA is the genetic material transferred during infection.

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

 

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