IB Biology HL 1.2.12 Directionality Question Bank

Practise IB Biology HL 1.2.12 by applying directionality concepts to exam-style questions.

Exam points

identify the relevant biological structure, process or evidence
apply the correct biological mechanism to the question
evaluate the result using data, adaptation or ecological reasoning

[Maximum number: 1]

The electron micrograph shows part of a cell in the pituitary gland of a rat. Ribosomes appear as dark granules. Some of the ribosomes are arranged in a linear array and some are in circles. The diagram shows how the ribosomes in a circular array are connected.

Figure for Question D1.2.12 (HL)—Directionality question 1 — IB Biology HL

Using the diagram, identify, with a reason, whether X or Y is the start codon.

Y is the start codon because translation goes from 5' to 3'

OR

Y is the start codon because it is in the $5^{\prime}$ end of the mRNA

OR

Y is the start codon because it is the first to enter the ribosomes;

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D1.2.12 (HL)—Directionality question 1