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Multiple Choice
Why are primers on the leading and lagging DNA strands removed rather than joined with Okazaki fragments during DNA replication?
A
Primers are removed to prevent the formation of double-stranded RNA.
B
Primers contain uracil, which is incompatible with DNA.
C
Primers are too short to be joined with Okazaki fragments.
D
Primers are made of RNA, which is not suitable for long-term stability in DNA.
Verified step by step guidance
1
Understand the role of primers in DNA replication: Primers are short sequences of RNA that provide a starting point for DNA synthesis. They are necessary because DNA polymerase can only add nucleotides to an existing strand of nucleic acid.
Recognize the difference between RNA and DNA: RNA contains the nucleotide uracil, whereas DNA contains thymine. This difference is crucial because uracil is not compatible with the long-term stability required for DNA.
Identify the process of primer removal: During DNA replication, the RNA primers are removed by enzymes such as RNase H and DNA polymerase I. This is because RNA is not suitable for the permanent structure of DNA.
Understand the synthesis of Okazaki fragments: On the lagging strand, DNA is synthesized in short segments called Okazaki fragments. These fragments are later joined together by the enzyme DNA ligase to form a continuous strand.
Clarify why primers are not joined with Okazaki fragments: Since primers are made of RNA, they are not stable enough to be part of the DNA strand. Therefore, they are removed and replaced with DNA nucleotides to ensure the integrity and stability of the DNA molecule.