Chargaff found that in double-stranded DNA, the number of guanine bases should be equal to the number of cytosine bases, and the number of adenine bases should equal the number of thymine bases. These rules proved to be important pieces of evidence for the idea of complementarity, the theory that each DNA base pairs only with a specific other base on its opposite strand.

According to Chargaff's rules, the statement regarding guanine and cytosine bases is correct. The two other statements that are similarly worded are not correct because they do not compare the frequencies of two bases that are complementary to each other (adenine will not bind cytosine and guanine will not bind thymine). Finally, guanine-cytosine bonds are more stable than adenine-thymine bonds.

An amino acid may be represented by multiple different codon sequences of base pairs of DNA. This codon degeneracy is what allows for the greater variability of DNA as compared to amino acid sequences.

For example, a DNA sequence may show variability without affecting the variability of the coded amino acids.

Organism 1 DNA: 5'-AAAGCAGGC-3' // Organism 2 DNA: 5'-AAGGCTGGT-3' // Differences: 3

Organism 1 RNA: 3'-UUU-CGU-CCG-5' // Organism 2 RNA: 3'-UUC-CGA-CCA-5' // Differences: 3

Organisms 1 Amino Acids: Phe-Arg-Pro // Organism 2 Amino Acids: Phe-Arg-Pro // Differences: 0

The backbone of DNA is made up of deoxyribose sugars linked to phosphate groups. These units are joined by phosphodiester bonds into chains. Nitrogenous bases are bound to the sugars of these groups and join DNA strands together by hydrogen bonds with their complementary base pairs.

Amino acids are the building blocks of proteins, and are not found in DNA. Alpha-linked glucose residues describe a type of polysaccharide, namely glycogen. Glycerol and fatty acids describe a type of lipid known as a triglyceride. Triglycerides and glycogen are primarily used in energy storage.

By looking at the name "phosphodiester bond" you should realize that a phosphate group is involved. A phosphodiester bond occurs between the phosphate group and a pentose sugar in the DNA backbone. The phosphate group from one nucleotide binds to the 3’ carbon on pentose sugar from the other nucleotide.

Nitrogenous bases are attached to the 1' carbon of the ring by a glycosidic linkage.

Remember that all nucleic acids contain nucleotides, composed of a pentose (a five-carbon sugar), a nitrogenous base, and a phosphate group. DNA and RNA must both contain a five-carbon sugar. RNA contains the pentose ribose, while DNA contains the pentose deoxyribose.

Glycogen does not contain a five-carbon sugar because it is made up of glucose subunits. Glucose contains six carbons.

ATP stands for adenosine triphosphate and GTP stands for guanosine triphosphate. Both of them are nucleic acids, meaning that they must contain a pentose sugar, a nitrogenous base, and phosphate groups. Both ATP and GTP contain three phosphate groups. The only difference between ATP and GTP is their nitrogenous base. ATP contains adenine whereas GTP contains guanine. Recall that adenine and guanine are both purines.

ATP and GTP do not contain any pyrimidines (cytosine, thymine, and uracil).

Polymerase chain reaction (PCR) is a technique used to generate thousands to millions of copies of a specific segment of DNA. There are three major steps to PCR. Denaturation occurs when heat separates the original DNA strand. Annealing follows, in which the DNA is cooled and primers bind to each separated strand. The final step is extension, in which DNA polymerase adds nucleotides to the 3' end of each primer. These steps are repeated for each PCR cycle.

Nucleotides are the monomers that make up nucleic acids. They are composed of a five-carbon sugar, a nitrogenous base, and a phosphate group. In building the polymer nucleic acid chain, the sugar and phosphate of one nucleotide align with those of another to build the phosphate-sugar backbone, while the nitrogenous bases will form hydrogen bonds across the helix to link two chains of nucleotides together. Phosphate groups carry negative charge; this gives the cell nucleus an overall negative charge and can be used to generate electrochemical gradients across the nuclear membrane.

Carboxylic acids are found in amino acids, and are not present in nucleic acids.

Adenosine triphosphate contains an adenine group, a ribose sugar, and three phosphates. ATP is known as the energy molecule since there is a lot of potential energy stored in the bonds between each of the three phosphate groups.

Hydrogen bonds form between electronegative atoms such as nitrogen and hydrogen atoms on their complementary bases between the DNA backbones. Adenine and thymine make two hydrogen bonds, while cytosine and guanine made three hydrogen bonds. Phosphodiester bonds keep the DNA backbone bonded together. Ionic and covalent bonds are too strong to bond the two antiparallel strands together since the strands must be separated during DNA synthesis. Hydrogen bonds are the perfect bond since they are weak individually, but collectively very strong.