Suggest how XLMTM causes elevated plasma creatine kinase (CK) levels.

XLMTM results from a sex-linked recessive mutation. In a male with XLMTM, where would this mutation be located? Select (✓) one box.

[ ] The homologous section of a Y chromosome

[ ] The homologous section of an X chromosome

[ ] The non-homologous section of a Y chromosome

[ ] The non-homologous section of an X chromosome

Scientists investigated the use of transplanted stem cells to treat XLMTM in mice. They set up four experimental groups:

• Group W – 60 wild-type mice (not affected by XLMTM)
• Group X – 60 mice with XLMTM
• Group Y – 60 mice with XLMTM that received stem cells from mice with XLMTM
• Group Z – 60 mice with XLMTM that received stem cells from wild-type mice

After 16 weeks, the scientists measured the quantity of creatine kinase in the blood plasma using a scale from 0 (normal) to ++++ (highest concentration). The results are shown in Table 1.

Table 1

Using all the information provided, evaluate the use of stem cells to treat XLMTM in humans.

The scientists carried out further work to investigate how the transplanted stem cells developed after transplantation.

• They transplanted stem cells from wild-type male mice into adult female mice with XLMTM.
• After 16 weeks, they found that plasma creatine kinase levels in these female mice had significantly decreased.
• On examining skeletal muscle tissue from the female mice, they found that some of these muscle cells contained a Y chromosome.

Suggest how the transplanted stem cells reduced plasma creatine kinase levels.