Both sickle-cell anPemia and Hutingrons disease are congenital lisorders. sickle-cell anaemia is the X linked in which one (β-chain of haemoglobin is diffmmi. 6th amino add of (β-chain is valine instead ot glutamic acid. Due to this patients haemoglobin level is reduced to hall of the normal and person becomes anaemic. Huntingtons disease is also due to presence of repetetive motifs, which occurs due to repetition of few residues,