In IB Biology SL D1.2.11, a base substitution can change a codon and the amino-acid sequence. The altered primary structure may change haemoglobin’s shape and function, as in sickle-cell anaemia.
Explain the causes and consequences of sickle-cell anemia.
(point) mutation of gene for hemoglobin;
CTC to CAC / GAG to GTG / substitution of T/thymine with A/adenine;
mRNA copy of gene is GUG instead of GAG;
valine instead of glutamic acid;
(in homozygotes) red blood cells become sickle-shaped;
(in homozygotes) less oxygen carried;
(in homozygotes) red blood cells do not survive long / burst / block blood vessels/capillaries / circulatory problems may cause pain/organ failure/example of symptom;
heterozygotes have malaria resistance;