Biology Cell Tissue Therapeutic Cloning
UDC Biology Cell Tissue Therapeutic Cloning Questions
problem enormous Cellt Tissue Engineering The potential of therapeutic cloning” has promise coupled Crth profound ethical problems. One question, raised after the cloning of Dolly by nuclear transfer to oocytes, was whether the cloned sheep would age normally. dampening hopes that cloning may be used someday to In 1998, it was reported that, indeed, Dolly’s telomeres were shorter than normal, Provide cells for cellular therapies. To address this issue, Lanza, et al. (Science 288, 2000) attempted a stringent In order to test this, they isolated fibroblasts from the dermis of adult steers and test: Could they derive healthy animals from cells kept in culture until cultured them until they were at or near senescence. The nuclei of these cells were the fetuses at six weeks of gestation and compared fibroblasts of the cloned fetuses transferred to enucleated oocytes, and five calf fetuses were produced. They removed with those of normal fetal calves of the That book Senescence? same developmental age. are Two PDs in fibroblasts Extra what chemicale could convent Fiber glasse to cells ?!
TABLE A.1 ESTETSDATOK Population doublings (PD) in fibroblasts derived from normal Seyfuses generated from clonal populations of adult fetuses and senescent cells. PDs left at time of nuclear transfer in original adult cells isolated from the fetus Cloned fetus 0.26 0.0 4.0 1.0 99.2 2.5 92.9 Normal fetus 59.6 67.4 90.1 91.4 89.3 2 60.2 59.8 55.7 The result of this experiment is shown in Table A.1. The five rows replicate data for each case:
(A) What conclusion would you draw regarding the life-span of a fibroblast from a cloned fetus, compared with that of a normally conceived fetus?
(B) What are the implications of this finding for tissue engineering? (Hint: Be spe- cific, and calculate a x-fold expansion that may be the result of this finding).
(C) In related experiments, the authors report that only 6 of the 1896 reconstructed oocytes would ultimately produce live offspring. With this in mind, what is an alternative explanation for the findings in Table A.1? How would you prove or disprove this theory?
(D) In Figure A.1 adapted from the Lanza paper, the authors compared the prolif- erative life-span of two different cell types: a fibroblast cell strain (BFF, grey line) and cells derived from the fetus that was cloned from late passage BFF cells (black line). Estimate the doubling time of each cell population during the first 40 days. How do these values compare to a normal cell cycle?
(E) Given your answer in part D, predict the fold increase in cell number after 100 days in culture (in the absence of senescence). (Hint: Use a simple equation.)
(F) How does this predicted fold increase in cell number compare to the fold increase seen in BFF donor cells?
(G) So, why do the BFF cells age? Telomere length! Telomere length was estimated animals , In Figure A.2, we see that telomere length (telomere restriction fragment size =TRF) actually increases when senescent cells (Figure A.2C, lanes 7 and 9) are cloned (lanes 8 and 10). What would be the predicted range of the “extended” life span of the cloned cells?
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