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Essay example - Cell Biology College
Pages 2 (502 words)
6. You are studying a strain of bacteria that carries a temperature-sensitive mutation in one of the genes required for DNA replication. The bacteria grow normally at the lower temperature, but when the temperature is raised they die. When you analyze the remains of the bacterial cells grown at the higher temperature you find evidence of partly replicated DNA…
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Where do you think the block to replication arises Choose the protein or protein complex below that is most likely responsible for the failure to replicate bacterial DNA. Give an explanation for your answer.
11 Most cells in the body of an adult human lack the telomerase enzyme because its gene is turned off and thus not expressed. An important step in the conversion of a normal cell into a cancer cell, which circumvents normal growth control, is the resumption of telomerase expression. Explain why telomerase might be necessary for the ability of cancer cells to divide over and over again.
The ends of the linear chromosomes are capped thus preventing further replication. Those capped ends of the chromosomes are called telomeres. The telomeric DNA contains the binding sites of the protein that protect the end of the chromosome. The enzyme telomerase has the ability to lengthen the telomeres. "With each cycle of cell division, the tips of telomeres drop off, until the chemical bookends become so eroded that the chromosomes become unstable, a condition that signals cells to stop dividing. This natural control on the cell division is called Hayflick limit. Cancers develop when cells incresingly ignores or overrides such signals of chromosome impairment."(O'Brien, 1999). ...
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