Mitosis is important for the repair of tissues. Explain what tissue repair means.
When a fully differentiated cell forms a tumour, uncontrolled cell division is one feature. Describe other features of tumour formation from a fully differentiated cell.
Telomeres prevent genes from being lost. Adult stem cells have chromosomes with long telomeres. Explain why having long telomeres is an advantage for cells that carry out many cell cycles.
Using Fig. 4.1, explain why GMP cells, which are progenitor cells, cannot be described as haematopoietic stem cells (HSCs).
Fig. 4.1 shows that monocytes differentiate into cell type $X$, which has a similar role to neutrophils. Name cell type $X$.
Cell type $Y$ shown in Fig. 4.1 releases molecules with antigen-binding sites. Name the molecules released by cell type $Y$.
T-lymphocyte differentiation starts in the bone marrow and continues in an organ called the thymus, where fully differentiated T-helper and T-killer cells are produced. In the thymus, T-lymphocytes that bind self antigens are destroyed. Explain why T-lymphocytes that bind to self antigens need to be destroyed in the thymus.