DNA structure
Edexcel GCSE Biology revision on DNA structure. Aligned to the Pearson Edexcel GCSE Biology 1BI0 specification. This bank has 5 practice questions on this topic.
Sample questions (3 of 5)
-
Question 1
What is the specific term for the twisted ladder structure of a DNA molecule?
- A) Primary helix
- B) Double helix
- C) Linear strand
- D) Triple spiral
Show answer
Answer: Double helix
The DNA molecule consists of two strands that wind around each other to form a spiral shape. This structure is universally referred to as a double helix in the GCSE specification.
-
Question 2
Which chemical component forms the backbone of the DNA strands?
- A) Sugar and base
- B) Phosphate base
- C) Sugar phosphate
- D) Protein phosphate
Show answer
Answer: Sugar phosphate
The sugar-phosphate backbone provides structural support to the DNA molecule. The nitrogenous bases are attached to the sugar molecules, not the phosphate groups.
-
Question 3
Which nitrogenous base always pairs with cytosine in a DNA molecule?
- A) Adenine bases
- B) Guanine bases
- C) Thymine bases
- D) Uracil bases
Show answer
Answer: Guanine bases
Complementary base pairing ensures that specific bases always bond together. Cytosine always pairs with guanine, while adenine always pairs with thymine to maintain the DNA structure.
Want to test yourself on the remaining cards for this topic?
2 more questions on DNA structure — plus mistakes tracking and spaced repetition across the whole Biology spec.
More Edexcel Biology topics
- Antibiotics & drug discovery
- Biodiversity & global warming
- Biotic & abiotic factors
- Blood vessels — artery / vein / capillary
- Blood — red cells, white cells, plasma, platelets
- Cancer
- Cell structure
- Classification
- Communicable diseases
- Coronary heart disease & lifestyle
- Cycles in ecosystems
- Decomposition