what 2 problems would exist if DNA ligase did not work?

Answer 1

One:
The mechanism of DNA ligase in connecting broken DNA strands is to form covalent phosphodiester bonds between 3' hydroxyl ends of one nucleotide with the 5' phosphate end of another. Without a proper functioning ligase, translation would not take place.

Two:
DNA ligase III: complexes with DNA repair protein XRCC1 to aid in sealing base excision mutations and recombinant fragments. Without ligase, a significant amount of point mutations would take place, thus causing pathogenicity.

Three:
Ligase also required for V(D)J recombination, the process which generates diversity in immunoglobulin and T-cell receptor loci during immune system development. Minus the Ligase, the immune system would be depressed and unable to defend against virulent microbes.

Answer 2

You would have problems with DNA synthesis, especially lagging strand synthesis.
You would have problems with DNA damage repair.