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Dołączył: 02 Cze 2006
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 Wysłany: Nie 19:34, 15 Paź 2006 Temat postu: dla b.ambitnych |
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A child presents with severe growth failure, accelerated aging that
causes adult complications such as diabetes and coronary artery disease,
and microcephaly (small head) due to increased nerve cell death. In vitro
assay of labeled thymidine incorporation reveals decreased levels of DNA
synthesis compared to controls, but normal-sized labeled DNA fragments.
The addition of protein extract from normal cells, gently heated to inactivate
DNA polymerase, restores DNA synthesis in the child’s cell extracts to
normal. Which of the enzymes used in DNA replication is likely to be
defective in this child?
a. DNA-directed DNA polymerase
b. Unwinding proteins
c. DNA polymerase I
d. DNA-directed RNA polymerase
e. DNA ligase
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