If a dna molecule is compared to a spiral staircase, what parts make up the steps?
sugar and nitrogen base
pairs of nitrogen bases
sugar and phosphate
pairs of sugars

The correct answer would be pairs of nitrogen bases.

DNA (deoxyribonucleic acid) is a double helical structure formed by two strands of DNA.

Deoxyribose sugar and phosphate are linked with phospho-di-ester bond and serve as the backbone of the DNA strands.

Nitrogenous bases are attached to the sugar with the help of glycosidic bond.

Nitrogenous base of one strand forms hydrogen bonds with the nitrogenous bases of the other strands to provide the stability to the structure.

cancer   is   essentially   uncontrolled   mitosis   of specialized cells

both male and female gametes are produced by meiosis of the germ cells. therefore, both male and female gametes are haploid. one male and one female gamete unite during the fertilization to form the diploid zygote. in seed bearing plants, pollen grain is the male gametophyte, which produces sperm cells.