Sickle Cell Disease

Edexcel AS-level BiologyDNA, Genes and Protein SynthesisLesson 19 of 20

Sickle cell disease is an inherited disorder caused by a single base substitution in the gene for the β-globin chain of haemoglobin.

In the DNA coding strand, the triplet for the sixth amino acid changes from GAG to GTG. In the mRNA the codon changes from GAG to GUG. As a result the amino acid glutamic acid is replaced by valine. This altered haemoglobin is called haemoglobin S (HbS); the normal form is HbA.

Key terms in this lesson

allele

One of the different forms of a gene, arising from mutation, that occupy the same locus on homologous chromosomes.

recessive

Describes an allele that is only expressed in the phenotype when no dominant allele of the same gene is present.

More in DNA, Genes and Protein Synthesis

• rRNA
• Protein Synthesis
• Transcription
• Translation
• Polysomes
• Mutations
• Gene Mutation
• Chromosome Mutations

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