Al Mawakeb School- Al Barsha Ap Biology Winter Break Assignment 2018-2019 _______________________________________________________________________________________ Question One: - Research about Hela cells, and explain how they differ from normal cells. Research about Philadelphia chromosome, and give a brief explanation. What is the difference between paralogous, orthologous, and analogous genes? Give examples. Question Two: Human cells divide every day for normal growth, replacement of cells, and tissue repair. The dividing cells proceed through the three phases of the cell cycle as shown in the figure above. When a person experiences a cut, damaged skin cells secrete a protein called epidermal growth factor (EGF). Epidermal (skin) cells in the vicinity of the injury possess proteins in their cell membranes called epidermal growth factor receptors (EGFR). (a) Identify the THREE major stages of interphase and describe these sequences in which they occur. (b) Describe the most likely role of EGF and the role of EGFR in a cell signaling pathway. Describe how the cellular response to EGF results in tissue repair. (c) Cancer can result from disruptions in cell cycle control. Mutations that increase the production of EGFR have been associated with skin cancer of the head and neck. Describe how a mutation outside of the coding region of a gene that encodes EGFR could lead to overproduction of EGFR protein in a skin cell. (d) In cases of skin cancer that are associated with over production of EGFR, treatment with antibodies against the extracellular portion of EGFR has been successful. Propose a model to explain how the antibody therapy most likely interferes with the cell signaling pathway, and give ONE reason the therapy is effective for treating cancer. Question 2 Both mitosis and meiosis are forms of cell division that produce daughter cells containing genetic information from the parent cell. (a) Describe TWO events that are common to both mitosis and meiosis that ensure the resulting daughter cells inherit the appropriate number of chromosomes. (b) The genetic composition of daughter cells produced by mitosis differs from that of the daughter cells produced by meiosis. Describe TWO features of the cell division processes that lead to these differences.