In D1.3.9, guide RNA directs Cas9 to a complementary DNA target. Cas9 cutting enables DNA to be deleted, inserted, replaced or disrupted; the selected HL question applies this to dystrophin.
Duchenne muscular dystrophy (DMD) is a sex-linked genetic disorder caused by a recessive allele resulting from mutations in the X-linked dystrophin gene. This causes the degeneration of cardiac and skeletal muscle. These mutations can include deletions, insertions and base substitution mutations.
Explain ways in which CRISPR-Cas9 gene editing could be used to change the mutated dystrophin protein produced.
a. gene editing requires a method for finding a target sequence in the genome/DNA/gene and replacing it with the desired sequence;
b. (gene editing could) change codon/point mutation/substitution that encodes/codes for a different amino acid (causing change in protein/dystrophin);
c. change codon that introduced a stop codon (making shorter peptide/dystrophin);
d. introduce DNA section/bases if mutation is a deletion;
e. delete DNA section/bases if mutation is an insertion;
a. both parts needed.