5. The mitotic cell cycle
A section of Biology, 9700
Listing 10 of 324 questions
shows a plant cell in a stage of mitosis. Some of the structures shown in contain DNA. Use a line labelled D on to indicate one of these structures. Name the stage of mitosis shown in . Colchicine is a chemical used by scientists to study mitosis. This chemical inhibits the organisation of the microtubules in prophase of mitosis. The cell shown in had not been treated with colchicine. Explain the evidence in that shows the cell had not been treated with colchicine.
9700_w24_qp_21
THEORY
2024
Paper 2, Variant 1
View
Adult stem cells are undifferentiated cells that are found in most animal tissues. Adult stem cells can divide by mitosis throughout their lifespan to form identical stem cells (self‑renewal) or to form cells that can differentiate into the functioning cells of that tissue. Mitosis is important for the repair of tissues. Explain what is meant by repair of tissues. Uncontrolled cell division is a characteristic feature of tumour formation from a differentiated cell. Describe other features of tumour formation from a fully differentiated cell. Telomeres prevent loss of genes. Adult stem cells have chromosomes with long telomeres. Explain why long telomeres are an advantage to cells that carry out many cell cycles. Haematopoietic stem cells (HSCs) are adult stem cells that are located in the bone marrow of bones. HSCs have a role in the formation of blood cells. is an outline summary showing the formation of some of the different types of blood cell that can be formed from HSCs. The first stage is the division of HSCs to produce progenitor cells. These cells are also able to divide by mitosis, but are not stem cells. Key = progenitor cells HSCs self- renewal HSCs immature red blood cells mature red blood cells platelets mature neutrophils monocytes immune response mature B-lymphocytes mature T-lymphocytes (T-helper and T-killer cells) Y X immature B-lymphocytes immature T-lymphocytes immature neutrophils immature monocytes megakaryocytes CMP cells GMP cells MEP cells Pre-T cells Pre-B cells CLP cells With reference to Fig 4.1, explain why GMP cells, which are progenitor cells, cannot be described as haematopoietic stem cells (HSCs). shows that monocytes differentiate into cell type X, which has a similar function to neutrophils. Name cell type X. Cell type Y shown in releases molecules with antigen binding sites. Name the molecules released by cell type Y. The differentiation of T‑lymphocytes begins in the bone marrow and continues in an organ known as the thymus to produce fully differentiated T‑helper and T‑killer cells. In the thymus, T‑lymphocytes that bind to self antigens are destroyed. Explain why T‑lymphocytes that bind to self antigens need to be destroyed in the thymus.
9700_w24_qp_22
THEORY
2024
Paper 2, Variant 2
View
When a section of lung tissue is viewed using a light microscope, it is possible to identify the trachea, the bronchus, the bronchioles and the alveoli. Other than differences in their diameters, describe one structural difference visible between: • the trachea and a bronchus • a bronchus and a bronchiole • a bronchiole and an alveolus. The mitotic cell cycle of the stem cells present in the gas exchange system is carefully controlled. During interphase of the mitotic cell cycle, cells grow by increasing in size. Complete Table 4.1 by: • listing, in order, the three phases that occur during interphase • stating one process, other than growth and respiration, that occurs in each of these three phases to help prepare the cell for mitosis. Table 4.1 phase process occurring during phase
9700_m20_qp_22
THEORY
2020
Paper 2, Variant 2
View
Questions Discovered
324