Earth's atmosphere is composed of about 78% nitrogen, 21% oxygen, and one percent other gases. These gases are found in layers (troposphere, stratosphere, mesosphere, thermosphere, and exosphere) defined by unique features such as temperature and pressure.
Genes are segments of DNA that are located on the chromosomes of each cell.
Explanation:
Chromosomes are basically tightly bundled thingies containing genes, DNA, whatever. Phenotype and genotype have nothing to do with chromosomes, that's just how WE describe them.