ConceptConceptDocsDocuments

IB Biology HL D1.2 Protein Synthesis Question Bank

Practise IB Biology HL D1.2 with sequence and expression questions covering transcription, translation, mRNA processing, genetic-code tables and mutation consequences.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • trace transcription and translation using promoters, codons, tRNA, ribosome sites and 5′–3′ directionality
  • explain splicing, non-coding DNA, alternative transcripts and post-translational protein modification
  • use genetic-code tables and mutation data to predict amino-acid changes and protein consequences

Covered syllabus points

D1.2.1—TranscriptionD1.2.2—Hydrogen bonding in transcriptionD1.2.3—DNA template stabilityD1.2.4—Transcription for gene expressionD1.2.5—TranslationD1.2.6—Roles in translationD1.2.7—Complementary base pairingD1.2.8—Genetic code featuresD1.2.9—Using genetic code tableD1.2.10—Elongation of polypeptideD1.2.11—Mutations changing protein structureD1.2.12 (HL)—DirectionalityD1.2.13 (HL)—Initiation of transcription at promoterD1.2.14 (HL)—Non-coding sequences in DNAD1.2.15 (HL)—Post-transcriptional modificationD1.2.16 (HL)—Alternative splicingD1.2.17 (HL)—Translation initiationD1.2.18 (HL)—Polypeptide modificationD1.2.19 (HL)—Amino acid recycling by proteasomes

D1.2 Protein synthesis question 1

[Maximum number: 5]

Auxin can be used to promote the development of roots from stem and leafy cuttings in some plants. In a study into the distribution of auxin in the development of these roots, scientists measured the amount of auxin in different leaves of a shoot tip of Petunia hybrida.

The figure indicates the numbering of leaves on the shoot, from L1 as the youngest and smallest to L6 as the largest and oldest leaf. The developmental stage of L5 and L6 was very similar, so L5 was not analysed. The stem base is the lowest part of the cutting where roots may form.

Figure for Question D1.2 Protein synthesis question 1 — IB Biology HL

The graph shows the auxin concentration in the different leaves.

Figure for Question D1.2 Protein synthesis question 1 — IB Biology HL

Question (a)

(a)

The scientists wanted to know whether the accumulation of auxin over time in the stem base of the controls affected expression of the GH3 gene, known to have a role in growth regulation in different plants. The technique that was used to quantify the level of transcription of the GH3 gene was Northern blotting. In this procedure the darkness and thickness of the band is an indicator of the level of transcription of a particular gene. The image shows the result of the Northern blot from 2 hours to 24 hours after cutting.

Figure for Question (a) — IB Biology HL
[ 5 ]

Question (i)

(i)

State the name of the molecule which is produced by transcription.

[ 1 ]

Question (ii)

(ii)

Compare the pattern of GH3 transcription with the pattern of auxin concentration in the stem base control cuttings. You may use the table provided to help you to record the patterns before you compare them. (Please note: a simple comparison in the table will not gain marks)

Table for Question (ii) — IB Biology HL
[ 2 ]

Question (iii)

(iii)

The scientists concluded that auxin activates the transcription of the GH 3 gene. Using the information on the auxin concentration in the stem base in the graph on page 4 and the Northern blot, evaluate whether this conclusion is supported.

[ 2 ]

D1.2 Protein synthesis question 2

[Maximum number: 1]

The sequence of bases on a short section of the antisense strand of a gene undergoing transcription is shown:

5′ CATG 3′5^{\prime} \text { CATG } 3^{\prime}

What is the sequence of bases on the resulting mRNA?

A

3′3^{\prime} CATG 5′5^{\prime}

B

5' GUAC 3'

C

3′3^{\prime} GUAC 5′5^{\prime}

D

3′GTAC3^{\prime} \mathrm{GTAC} 5'

All question bank results loaded