Based on the computer simulation, in what stage of the cell cycle to cells spend

Question

Based on the computer simulation, in what stage of the cell cycle to cells spend the least amount of time? Give a quantitative answer. Explain how you were able to distinguish between onion root tip cells in late Anaphase from cells in Telophase. The Bio 1 instructors are sometimes asked why we don't have you perform a karyotype on your own cells. Assume that the techniques required are within your range of experience (they are listed in the lab manual). Why do you think performing individual karyotypes in lab is not a good idea? There are many possible answers; your rationale is important. Include citations if you are using material for reference. Cystic fibrosis (from the electrophoresis lab) is caused by a mutation m the CFTR gone on chromosome 7. If a fetus was genetically analyzed and it was found that there were 2 and only 2 copies of chromosome 7, does that mean tin fetus does NOT have cystic fibrosis? Explain why or why not.

Explanation / Answer

6. Ans: Anaphase is the shortest phase of mitosis. In anaphase, the sister chromatids are pulled apart to opposite ends of the cell. Here the cells divide quickly because the dna is unwrapped and is most susepitable to dammage so the cell attempts to divide and wrap the dna up again as quickly as possible.

7. Late anaphase: The centromere divides allowing the sister chromatids to begin to move apart. At this point since the chromatids have separated and each has its own centromere they are each called a chromosome. The chromosomes have begun to move to their respective poles. Chromosomes are visible and the spindle. In late anaphase the chromosomes have arrived at the opposite poles.

Telophase: The reached chromosomes will uncoil and gradually become less visible. The nuclear envelope will be reformed around each complete set of uncoiling chromosomes. The nucleolus will once again become visible. Look for a cell in which the chromosomes have arrived at their respective poles.

8. Ans:

(The preparation required for karyotyping depends on the method your doctor will use to take a sample of your blood cells for testing. You could have blood drawn, a bone marrow biopsy (taking a sample of the spongy tissue inside certain bones), amniocentesis (taking a sample of amniotic fluid from the uterus), or another procedure. Rarely, complications can result from these testing methods. There is a slight risk of bleeding and infection from having blood drawn or having your bone marrow biopsied, and amniocentesis carries a very minimal risk of miscarriage. If you are undergoing chemotherapy, your test results may be skewed. The chemotherapy process can cause breaks in your chromosomes, which will appear in the resulting images. Abnormalities that appear in a test sample could be the result of any number of genetic syndromes or conditions. Sometimes an abnormality will occur in the lab sample that is not reflected in the patient’s actual body. In order to confirm that an abnormality is present in the patient, the karyotype test can be repeated).

9. Ans: A person must inherit two copies of a defective CF gene - one copy from each parent to have the disease. People who inherit only one copy are considered CF carriers and do not have the disease, but they can pass their copy of the defective gene on to their children.

But here in the above case the foetus may be identified as the presence of CF with Uniparental disomy (Uniparental disomy represents a departure from the usual situation in which one member of each pair of chromosomes (called homologous chromosomes) is normally inherited from each parent. Thus, for each of the 23 pairs of human chromosomes, one is normally inherited from the father and the other from the mother). It can be concluded that, the the foetus is having CF with abnormal situation of Uniparental disomy (UPD) in which both members of a chromosome pair are inherited from one parent, and the other parent’s chromosome pair might be be missing.

If the inherited two copies of chromosome 7 is from the CF carier parent, there may be a chances of missing or escape of the disease in the foetus/child, but they can pass their copy of the defective gene to next generation.

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