Answer:
1. The 2 bases forming each rung of the 'ladder' snap apart. This is caused by an enzyme that passes along the strands, 'unzipping' it
2. Spare nucleotides (in the nucleus of the cell) attach themselves to the 'broken rungs' to repair the break. Each repairing nucleotide is identical to the broken one
3. As each 'broken rung' is repaired, two 'ladders' form, that is 2 identical strands of DNA. The 'repairing' is really the process of replica
Explanation:
Hope this helps!
1. mother to fetus 2. through exposure to the antigen (virus, toxins, or cancer cells).
Increases genetic variation, which in and of itself has extreme benefits such as protection against disease, capability to evolve, etc