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IB Biology SL D1.2 Protein Synthesis Question Bank

Practise IB Biology SL D1.2 by tracing DNA to mRNA and codons to amino-acid sequences at the ribosome, using strand orientation and the genetic code.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • explain transcription using a DNA template, complementary RNA nucleotides and RNA polymerase
  • explain translation through codon-anticodon pairing, tRNA delivery and peptide-bond formation at ribosomes
  • derive RNA or amino-acid sequences while respecting strand orientation, start signals and the genetic code

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 structure

D1.2 Protein synthesis question 1

[Maximum number: 4]

Mitosis produces genetically identical cells, which become specialized by expressing specific genes. This ensures that tissues and organs are adapted to their functions.

Describe how mRNA is produced in the nucleus.

D1.2 Protein synthesis question 2

[Maximum number: 1]

The gene that codes for a particular polypeptide includes the base sequence shown.
GAGTACCCT
What is the base sequence of the mRNA molecule which is complementary to this sequence?

A

GAGTACCCT

B

CTCATGGGA

C

GUGTUCCCT

D

CUCAUGGGA

D1.2 Protein synthesis question 3

[Maximum number: 7]

Rice (Oryza sativa) is usually intolerant to sustained submergence under water, although it grows rapidly in height for a few days before dying. This is true for one variety, Oryza sativa japonica. The variety Oryza sativa indica is much more tolerant to submergence.

Three genetically modified forms of O. sativa japonica, GMFA, GMFB and GMFC, were made using different fragments of DNA taken from O. sativa indica.

The plants were then submerged for a period of 11 days. The heights of all the plants were measured at the beginning and at the end of the submergence period.

Figure for Question D1.2 Protein synthesis question 3 — IB Biology SL
Figure for Question D1.2 Protein synthesis question 3 — IB Biology SL

Question (a)

(a)

In the same experiment, the researchers hypothesized that the capacity to survive when submerged is related to the presence of three genes very close to each other on rice chromosome number 9; these genes were named Sub1A, Sub1B and Sub1C. The photograph below of part of a gel shows relative amounts of messenger RNA produced from these three genes by the submergence-intolerant variety, O. sativa japonica, and by the submergence-tolerant variety, O. sativa indica, at different times of a submergence period, followed by a recovery period out of water.

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

Question (i)

(i)

Determine which gene produced the most mRNA on the first day of the submergence period for variety O. sativa japonica.

[ 1 ]

Question (ii)

(ii)

Outline the difference in mRNA production for the three genes during the submergence period for variety O. sativa indica.

[ 2 ]

Question (iii)

(iii)

Compare the mRNA production for the three genes during the submergence period between the two varieties.

[ 2 ]

Question (b)

(b)

Deduce, using all the data, which gene was used to modify GMFC.

[ 2 ]
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