The level of dna packaging brought about by the formation of looks like beads on a string.

The level of DNA  packaging brought about by the formation of nucleosomes looks like beads on a string. 
 The DNA packaging process includes and describes how DNA is packaged so tightly into chromosomes and squeezed into a tiny nucleus.
A nucleosome is a section of DNA that is wrapped around a core of proteins.

Leaves specifically the gas exchange between plants and the environment. while plants undergo photosynthesis, they also partake in cellular respiration. respiration is the process that happens in the leaves of plants.