- 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.
(a) Using a Punnett grid, deduce the probability of inheriting DMD if an unaffected male has offspring with a female carrier. [3]
(b) Distinguish between deletion and insertion mutations. [1]
(Question 7 continued)
Gene editing technologies using CRISPR (clustered regularly interspaced short palindromic repeats) can potentially treat various diseases such as DMD. CRISPR-Cas9 can be used to repair the mutated DMD gene, leading to the expression of the encoded protein, dystrophin.
The diagram shows the correction of dystrophin expression by gene editing.
(c) Explain ways in which CRISPR-Cas9 gene editing could be used to change the mutated dystrophin protein produced. [3]
(d) Suggest one reason for the use of pluripotent instead of multipotent stem cells in this process. [1]