Question

27. ?-thalassemia is a monogenic disease characterized by different types of mutations in the HBB gene that influence the severity of the disease. Specify a mutation that will cause a mild disease and one that will cause a severe disease.

Extra credit:

Read: “Paternal transmission of a FMR1full mutation allele”. Alvarez-Mora et al. Am J Med Genet. 2017; 173A: p2795-2797.

BRIEFLY explain how the patient displayed the fragile X phenotype while only inheriting 88 CGG repeats from her father.

Answer 1

27). The beta-thalassemia trait is inherited in the autosomal recessive pattern. The homozygotes are normal, heterozygotes show the mild symptoms of the beta-thalassemia showing the co-dominance pattern, whereas the presence of two recessive traits causes severe beta-thalassemia.

People with hemoglobin C/?⁺⁺ or C/?⁺  thalassemia (produces some beta-globin, but less than the normal) produces a milder disease, whereas those with C/?⁰ (produces no beta-globin) produces severe symptoms.