You have discovered several mutant strains of E. coli. Each mutant exhibits a de
ID: 88725 • Letter: Y
Question
You have discovered several mutant strains of E. coli. Each mutant exhibits a defect in DNA replication:the defects arc listed below. For each defect list the enzyme and/or enzyme activity that is being affected by the mutation. Be as specific as possible! a) Newly synthesized DNA contains many mismatched bases. b) RNA primers are removed, but Okazaki fragments persist, and DNA synthesis is never completed. c) No initiation occurs. d) DNA Synthesis is very slow. e) RNA primers are never removed.Explanation / Answer
Answer:
a. No repair from DNA Polymerase III and or DNA Polymerase I
b. DNA ligase is not joining the deoxyribonucleotides to connect Okazaki fragments.
c. This can happen if there is no primase activity.
It may also happen that helicase is not separating the 2 strands of DNA, or there is not enough ATP in the cells leading to no DnaA-ATP complexes which initiate DNA replication, or initiator proteins that recognize DNA sequences specific to origins and that recruit other proteins such as helicase, are not working. Defect in DNA polymerase may also be a reason.
d. Only DNA polymerase 1 activity is present.
e. Defect in DNA polymerase I which is not removing RNA primers at the start of each Okazaki fragment.
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