Question

Describe/identify ways that replication can go wrong, the results (in general) and what

the cell does to fix these errors

Answer 1

DNA replication errors can lead to mutations, instability, and cell death. Cells use proofreading, mismatch repair, and other mechanisms to fix these errors and maintain genome integrity.

Replication errors and cellular responses:

Errors during DNA replication can occur in several ways:

1. Base pair mismatches: Incorrect insertion of nucleotides during replication.
2. Insertions/deletions: Addition or removal of nucleotides from the DNA sequence.
3. Strand slippage: Misalignment of the DNA strands during replication, leading to insertions or deletions.
4. Damage to DNA template: Chemical or physical damage to the DNA molecule before or during replication.

General results of replication errors:

• Mutations: Permanent changes in the DNA sequence, potentially leading to:

1. Loss of function: If the mutation disrupts an important gene.
2. Gain of function: If the mutation creates a new, potentially harmful gene.
3. Cancer: Accumulation of mutations can lead to uncontrolled cell growth.

• Genome instability: Increased susceptibility to further mutations.
• Cell death: If the errors are too severe, the cell may not be able to survive.

Cellular mechanisms to fix replication errors:

1. Proofreading: DNA polymerases have a built-in proofreading function to detect and correct mismatched base pairs immediately after insertion.
2. Mismatch repair: Specialized enzymes identify and remove mismatched base pairs that escaped proofreading.
3. Excision repair: Nucleotide excision repair removes damaged nucleotides from the DNA strand, followed by gap filling with correct nucleotides.
4. Base excision repair: Removes damaged bases and replaces them with the correct ones.
5. Double-strand break repair: Repairs breaks in both strands of the DNA molecule.

Overall:

Cells have a complex and efficient system to detect and repair errors during DNA replication. This helps to maintain the integrity of the genome and prevent the harmful consequences of mutations. However, these mechanisms are not perfect, and some errors can escape detection and repair, leading to mutations and potentially serious consequences for the cell and organism.