Dna is wrapped around proteins called to form a chromosome.

Histones

Histones are the specialized proteins found in the eukaryotic genomic conformation. These proteins keep the DNA double helical strands in winded state. The conformation gets simplified in an unwinded state to conduct DNA replication.

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%