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IB Biology SL D1.3.2 Base Substitution Consequences Questions

Use exam evidence to trace a DNA base substitution through mRNA and amino acid sequence to protein and sickle-cell effects in IB Biology SL D1.3.2.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Trace a base substitution from the DNA triplet through the mRNA codon to a changed amino acid or polypeptide.
  • Explain how the sickle-cell base substitution replaces glutamic acid with valine and changes haemoglobin or red-cell function.
  • Distinguish silent and changed-protein outcomes when a base substitution alters a codon, using the genetic-code evidence.

IB Biology SL D1.3.2 Base Substitution Consequences Questions question 1

[Maximum number: 2]

Thrombophilia is a human genetic condition where the blood has an increased tendency to clot. The condition is caused by a single base substitution mutation in DNA. If a person is homozygous for the gene, they are at greater risk for developing a blood clot than an individual who is heterozygous. The pedigree chart shows the inheritance of thrombophilia in a family.

Figure for Question IB Biology SL D1.3.2 Base Substitution Consequences Questions question 1 — IB Biology SL

Explain how a single base substitution mutation in DNA can cause a change to a protein.

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