Final answer:
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The DNA polymerase I Klenow fragment is missing 5' to 3' exonuclease activity.
The Klenow fragment of DNA polymerase I lacks the 5' to 3' exonuclease activity, crucial for RNA primer removal and involved in DNA repair, but it maintains other vital functions for DNA replication.
Thus option d) 5' to 3' exonuclease is correct answer.
Step-by-step explanation:
The DNA polymerase I Klenow fragment is missing 5' to 3' exonuclease activity. This is the activity responsible for removing RNA primers during DNA replication and is also involved in some DNA repair processes.
The Klenow fragment retains both the 5' to 3' DNA synthesis activity, which adds nucleotides in the 5' to 3' direction, and the 3' to 5' exonuclease activity, which is the proofreading function that removes incorrect nucleotides.
In contrast, the endonuclease activity is not a characteristic of DNA polymerase I Klenow fragment and is associated with cutting DNA strands at specific internal sites.
Thus option d) 5' to 3' exonuclease is correct answer.