Final answer:
During DNA replication, seven key issues include unwinding of the double helix, reducing supercoiling, synthesizing RNA primers, maintaining the direction of synthesis, creating Okazaki fragments on the lagging strand, proofreading errors, and replacing RNA primers with DNA to ensure an accurate replication process.
Step-by-step explanation:
Key Issues in DNA Replication
During DNA replication, several key issues must be resolved to ensure the process is accurate and complete. Here are seven critical issues:
- Unwinding the DNA helix - The double-stranded DNA must be unwound to allow the replication machinery access to the template strands.
- Reducing supercoiling - The unwinding process causes supercoiling, which must be relieved by enzymes such as DNA topoisomerases.
- Primer synthesis - RNA primers are synthesized by primase to provide starting points for DNA polymerase.
- Direction of synthesis - DNA polymerases can only add nucleotides in a 5' to 3' direction, which complicates synthesis on the lagging strand.
- Okazaki fragments - On the lagging strand, DNA is synthesized discontinuously in short segments called Okazaki fragments.
- Proofreading and error correction - DNA polymerases possess proofreading abilities to correct errors during replication.
- Replacement of RNA primers with DNA - Once replication is underway, RNA primers must be removed and replaced with DNA.
These issues are critical for the replication process to produce two identical copies of the DNA molecule, thus ensuring genetic consistency during cell division.