<prompt> Sickle cell disease is present with which mutation:Cross-linked defectBase pair defectMismatch defectBase pair substitution  <response>: Ans. d Base pair substitutionRef: Harpers Biochemistry, 30th ed. pg. 416-17A partial missense mutation type of base pair substitution glutamic acid, the normal amino acid in position 6 of the b chain, has been replaced by valine. 