1. Patau syndrome is a rare disease that results from having an extra chromosome
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Question
1. Patau syndrome is a rare disease that results from having an extra chromosome 13 in all cells. Most infants with this disease die within the first few weeks of life, as severe defects in many organ systems result. A defect in the formation of chiasma during meiosis I could lead to the production of egg cells with two copies of chromosome 13. Explain why this is and describe how many copies of chromosome 13 each of the 4 meiotic products will have in this situation at the end of meiosis II.
2. Taxol is an anti-cancer drug that prevents uncontrolled cell proliferation by stabilizing microtubules, so Taxol treatment causes cells to arrest (which they get stuck) in the cell cycle. Which phase of the cell cycle would the cells become arrested in and why?
Explanation / Answer
Answer:
Patau syndrome is a rare disease that results from having an extra chromosome 13 in all cells. Most infants with this disease die within the first few weeks of life, as severe defects in many organ systems result. A defect in the formation of chiasma during meiosis I could lead to the production of egg cells with two copies of chromosome 13.
In this condition, at the end of meiosis II, out of four cells, two cells will be normal, one cell will have one extra chromosome 13 and other daughter cell will not have any extra chromosome. This is because, during the cell division, the homologues chromosomes exchange their genetic material leads to the formation of chiasma. During this process, the two homologous chromosomes are pulled to each pole of the cell.
2. The cell will become arrested in the G1 phase of the mitotic cell cycle. This is because of the blockage of chromosomes and they fail to resume anaphase. The segregation of cell totally fails results in the death of cell by apoptosis.
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