The number of protons in the nucleus is equal to atomic number, Z while the number of neutrons in the nucleus is sometimes called neutron number, N. Mass number gives the approximate atomic mass of the element. For example, mass number of magnesium is 24 as it contains 12 protons and 12 neutrons in its nucleus.
DNA also includes sugars and phosphate groups that make the phosphate-deoxyribose backbone. If you think of the structure of DNA as a twisted ladder, the rungs of the ladder are made from the nitrogenous bases.These bases pair up to make each step of the ladder. They also only pair up in a specific way.NA also includes sugars and phosphate groups that make the phosphate-deoxyribose backbone. If you think of the structure of DNA as a twisted ladder, the rungs of the ladder are made from the nitrogenous bases.
The two sides of the DNA ladder are held together loosely by hydrogen bonds (see the small dots down the middle of the double helix). The DNA can actually unzip when it needs to replicate-or make a copy of itself. DNA needs to copy itself when a cell divides, so that the new cells each contain a copy of the DNA.he sides of the ladder are made of alternating sugar and phosphate molecules. The sugar is deoxyribose. The rungs of the ladder are pairs of 4 types of nitrogen bases.Two of the bases are purines-adenine and guanine. The pyrimidines are thymine and cytosine.