Because the vasculary bundles are sectioned and sieve can't pass through to feed the organs of the plant.
Yes it absolutely makes sense and it is correct. Although there are many more definitions of a gene out there but this one is not wrong.
Sugar , phosphate , and one of the 4 bases (adenine ,guanine,cytosine,thymine)
Plasmids, they are rings of DNA often used in procedures like insulin production and cloning
