Question

Explain why a DNA polymerase that could synthesize DNA in the$\mathbf{\text{3'}}\mathbf{\to }\mathbf{\text{5'}}$ direction would have a selective disadvantage even if it had$\mathbf{\text{5'}}\mathbf{\to }\mathbf{\text{3'}}$ proofreading activity

Short answer

The $\text{5'}\to \text{3'}$exonuclease results in the hydrolytic removal of a mispaired nucleotide, leaving a 3’ $\text{- OH}$or monophosphate group at the$\text{5'}$ end of the DNA strand.

Step-by-step solution

Define DNA polymerase

The enzyme that is involved in the duplication of the DNA molecules during the replication process to create two identical double stranded DNA molecules is known as DNA polymerase.

Disadvantage of  5’ to 3’ exonuclease

The$\text{5'}\to \text{3'}$exonuclease removes a mispaired nucleotide hydrolytically from the DNA. It leaves an$\text{- OH}$ at 3’ end or monophosphate group at the_$\text{5'}$end of the DNA strand.

Therefore, to activate the proofreading activity in $\text{5'}\to \text{3'}$ a direction, more ATP will be required