Tazswana’s Story by S. Catherine Silver Key

Handout 2—β-Globin Inheritance Pattern

Figure 2-1. Tazswana Williams’s Family Pedigree

Pedigree KEY
= allele with single base substitution in β-globin exon: amino acid substitution results.
= allele with single base substitution in intron: splicing defect results.
= allele with large deletion removing β-globin promoter: one allele not expressed.
= wild type allele.

Questions

  1. The predominant inheritance pattern for β-thalassemia major and intermedia are inherited in an autosomal recessive pattern. List the individuals in Tazswana’s pedigree chart who are carriers for β-thalassemia. (Note: assume Tazswana is the only family member with symptoms.)
  2. List the individuals in the chart who are indicated as heterozygous for the β-globin gene. Explain your answers. (Note: heterozygous = more than one type of allele; “wild-type” is a normal allele; each type of mutation is an allele. Terms to learn: heterozygote, compound heterozygote (two mutant alleles).)
  3. Explain why only Tazswana has the disease.
  4. Speculate on why a mutation in the non-coding, intron region of the β-globin gene could produce a defective β-globin protein.

Go to Handout 3—“Beautiful Baby”

Originally published at http://www.sciencecases.org/tazswana/tazswana2.asp

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