Question

1. You're currently working with two boys who have muscular dystrophy. One patient is much more severely affected than the other. The boy who is more severely affected has a two-base insertion at the beginning of his dystrophin gene. The boy who is less severely affected has the same two-base insertion but also has a third base inserted just a few bases away. Explain why the second boy's illness is milder.

Answer 1

Q.1. Answer-

1. The boy who is severely affected by muscular dystrophy has two base inserts the beginning of his dystrophin gene. This insertion causes frame shift mutation because insertion of base changes reading frame of gene and mutated gene will produce mutated mRNA. This mutated mRNA will produce abnormal protein. Here the insertion is at the beginning of the dystrophin gene so that whole genes open reading frame changes that results in completely different mRNA and completely different protein. So that this boy is severely affected.

2. The boy who is less affected by muscular dystrophy has same two base insertion but also third base inserted just few bases away because the effect of frame shift mutation is reduced by this third base insertion. Initially the two base insertion results in synthesis of completely unrelated protein as mutation occurs as the beginning of the gene. But third base is then inserted just few bases away resets open reading frame as normal because codons are readed in set of three bases and after insertion of this third base open reading frame is shifted by three bases and after this point mutation rest all has normal open reading frame. This boy shows milder illness because only few amino acids are different than wild type protein because two base insertion shifts open reading frame by two bases that codes for different amino acids and when third base is inserted open reading frame is shifted by three bases that does not affect open reading frame of gene and from this point normal protein is synthesized. In this boy protein with few amino acids are changed is produced so that he will be less affected because this small change may not affect proteins entire function.