Stem cells from adult bone marrow can form many types of cells including…

The idea

Adult stem cells are unspecialised cells found in tissues such as bone marrow. They divide by mitosis and differentiate into a limited range of specialised cells, for example red and white blood cells (as well as forming cell fragments called platelets). This makes bone marrow important for replacing blood cells throughout life. A bone marrow transplant can introduce healthy stem cells into a patient, for example to treat leukaemia, where donated stem cells divide and differentiate to restore healthy blood cell production. The statement stresses two ideas: the source is adult bone marrow, and the resulting cells include blood cells. Adult stem cells cannot form every cell type, so their potential is described as limited rather than unlimited.

What earns the marks

• State that adult stem cells are unspecialised cells that can divide by mitosis.
• Identify bone marrow as a source of adult stem cells.
• Explain that these stem cells can differentiate into several types of specialised cell.
• Give blood cells, such as red blood cells or white blood cells, as examples of specialised cells formed from bone marrow stem cells.
• Link bone marrow stem cells to the continuous replacement of blood cells or to treatments such as bone marrow transplants.

Common mistakes and how to put them right

• Saying adult stem cells can become any cell type in the body.

  Put it right by stating that adult stem cells can form only a limited range of cell types.

• Confusing differentiation with cell division.

  Put it right by explaining that mitosis produces more cells, whereas differentiation makes a cell specialised.

• Claiming that bone marrow stem cells only make red blood cells.

  Put it right by including white blood cells as further examples of specialised cells, and platelets as cell fragments.

Exam tips

• Use the phrase limited range of cell types when describing adult stem cells.
• Name at least one specific blood cell type (e.g., red or white blood cell) to make the answer precise, remembering that platelets are cell fragments, not true cells.
• If asked to compare stem cell types, contrast the limited potential of adult stem cells with the wider potential of embryonic stem cells.