The phosphate backbone of DNA is negatively charged due to the bonds created between the phosphorous atoms and the oxygen atoms. Each phosphate group contains one negatively charged oxygen atom, therefore the entire strand of DNA is negatively charged due to repeated phosphate groups. 

Nitrogen is essential to create all the nucleic acids, and phosphorous is essential to create phospholipids (an obvious choice), ATP and ADP (they are the same class of molecule, and the P stands for phosphate), and DNA (for the phosphate-sugar backbone).

DNA is a polymer composed of nucleotide monomers. Each nucleotide is formed from a deoxyribose sugar, a phosphate, and a nitrogenous base. There are two types of nitrogenous bases: purines and pyrimidines. The purines are adenine and guanine, while the pyrimidines are thymine and cytosine (and uracil). Adenine will always bind thymine and cytosine will always bind guanine. Uracil is only found in RNA, and is absent from DNA.

During DNA replication and synthesis, nucleotides align so that the nitrogenous bases are correctly paired. The bases bind to one other via hydrogen bonding to secure the nucleotide to the template strand. The protein DNA ligase then fuses the sugar-phosphate groups of adjacent nucleotides to create the DNA backbone. These bonds are known as phosphodiester bonds.

The only false statement concerns the identity of bonding between nitrogenous bases. Bases are held together by hydrogen bonds, and the DNA backbone is held together by phosphodiester bonds.

The bond formed between the sugar of one nucleotide and the phosphate of an adjacent nucleotide is a covalent bond. A covalent bond is the sharing of electrons between atoms. A covalent bond is stronger than a hydrogen bond (hydrogen bonds hold pairs of nucleotides together on opposite strands in DNA). Thus, the covalent bond is crucial to the backbone of the DNA. 

Uracil is bound to adenine in the production of RNA, while thymine is used in its place in the production of DNA. Adenine, guanine, and cytosine are all used in the production of both RNA and DNA.

Cytosine and guanine form three hydrogen bonds between each other, while tyrosine and adenine form two hydrogen bonds. We simply need to count how many of each base we have and multiple cytosine and guanine by three, and thymine and adenine by two.

CGTTTGAC has 2 cytosine, 2 guanine, 3 thymine, and 1 adenine.

DNA and RNA are made of nucleotides, which contain oxygen, hydrogen, nitrogen, carbon, and phosphorus. The nucleic acid backbone is comprised of sugars, made of carbon, hydrogen, and oxygen, and phosphate groups, made of phosphorus, hydrogen, and oxygen. The backbone binds to bases, which contain a nitrogen element.

Potassium is not found in nucleic acid structure, and is used in other parts of the body like muscles and nerves for signal propagation.

This question is mostly about the differentiations between a nucleoside and a nucleotide. A nucleoside is composed of a nitrogenous base and a ribose or deoxyribose sugar. A nitrogenous base, a ribose/deoxyribose sugar, and a phosphate describe a nucleotide. Remember that nucleosides are incomplete nucleotides, and lack a phosphate group.

Cytosine and guanine, when base paired, have three hydrogen bonds between them. Adenine and thymine only have two. This extra hydrogen bond helps make the cytosine-guanine pair favorable because it increases stability, and reduces bond energy.

Ionic and covalent bonds do not occur between nitrogenous bases in DNA. Covalent bonds are found in the DNA backbone (known as phosphodiester bonds).

Due to DNA's double-helical structure, the nucleotide bases are paired. Adenine is paired with thymine and guanine is paired with cytosine. Chargaff found that there is typically an equivalent number of adenine and thymine bases, and an equivalent number of guanine and cytosine bases. In a given sample of DNA, all adenine residues will have thymine counterparts on the complementary strand, and all cytosine residues will have complementary guanine counterparts. As a result, there will be equal numbers of each residue of the base pair in any sample of double-stranded DNA.