IB Biology HL A1.2 Nucleic acids questions

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Question 1

Multiple choiceEasy1 mark

During molecular visualization of chromatin, a student selects a DNA–protein unit for closer study. Which arrangement in the model represents a nucleosome?

Show answer and explanation

Answer: C. A nucleosome has DNA wrapped around a core of eight histone proteins, with an additional histone attached to linker DNA.

A: uses seven histone proteins in the core instead of eight. B: places the additional histone on the core rather than on linker DNA. D: omits the additional histone attached to linker DNA.

Remember: distinguish the eight-protein core from the additional linker-associated histone.

Question 2

Paper 2Easy4 marks

Figure 1 shows the number of possible DNA base sequences for strands of different lengths.

12340163248648096112128144160176192208224240256Length of DNA strand / nucleotide positionsNumber of possible base sequences41664256
(a)

Use Figure 1 to state the number of possible DNA base sequences for a strand of four nucleotide positions.

[1]
(b)

Use the pattern in Figure 1 to explain how a short DNA molecule can store a large amount of information.

[1]
(c)

Explain how complementary base pairing, based on hydrogen bonding, allows genetic information to be replicated and expressed.

[2]

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