DNA, RNA, and Proteins - AP Biology

The diagram depicts two purines (adenine and guanine), identifiable by their pyrimidine-imidazole double-ring structure. Pyrimidines (such at thymine and cytosine) have only one ring, amino acids have both amine and carboxylic acid groups, and ribose and deoxyribose are pentameric sugars (and contain no nitrogen).

The bonding that occurs between two parallel strands of nucleic acids in DNA is hydrogen bonding. As you know, hydrogen bonding occurs between molecules containing fluorine, nitrogen and oxygen with other fluorine, nitrogen and oxygen atoms. This is a fairly weak bond but there are so many hydrogen bonds along a strand of DNA making the attachment between the two quite strong, but the two strands can still be separated as needed (during replication and transcription). Adenine and thymine form two hydrogen bonds, while cytosine and guanine form three hydrogen bonds.

Hydrogen bonds between nucleotides of different strands are crucial for the stability of DNA. Adenine and thymine pair up with two hydrogen bonds between the nucleotides. On the other hand, cytosine and guanine pair up with three hydrogen bonds between the nucleotides.

In order to solve this problem, it is imperative that you remember that RNA replaces thymine with uracil. This automatically eliminates three of the answer choices. Next, the RNA strand must have nucleotides that pair up with the DNA nucleotides (adenine pairs with thymine and cytosine pairs with guanine). For example, if DNA has a nucleotide of G, the RNA would have a nucleotide of C. Finally, since the strands must be antiparallel to one another, the mRNA must start with a 5' and end with a 3'. Thus, our answer is 5'-UAGGGUCCAUGG-3'.

Below is a side by side comparison:

3'-ATCCCAGGTACC-5' (DNA)

5'-UAGGGUCCAUGG-3 (mRNA)

There are two types of bases in DNA: purines and pyrimidines. The purines are adenine and guanine. The pyrimidines are cytosine and thymine (note that uracil is also a pyrimidine, but is only found in RNA). Adenine forms two hydrogen bonds with thymine, and guanine forms three bonds with cytosine. As a result, cytosine/guanine-rich regions in DNA require more energy to denature. One was to remember which bases are purines is through the use of the mnemonic "Pure As Gold". Another mnemonic to help you remember which nitrogenous bases are pyrimidines are that: pyrimidines, like pyramids, are sharp, and sharp things CUT (Cytosine, Uracil, and Thymine).

If the imaginary DNA is ten percent adenine, then that means there must be ten percent thymine because they are complementary to one another. The rest of the eighty percent of the DNA strand must be made up of guanine and cytosine. Because they are complementary to each other, half will be guanine and half will be cytosine. This means that there will be forty percent guanine present in the DNA strand.

If the RNA is thirty percent guanine, then that means it must be composed of thirty percent cytosine because they are complementary to each other. The other forty percent of the RNA strand is made up of adenine and uracil. Because they are complementary to each other, half will be adenine and the other half will be uracil. This means that there will be twenty percent uracil present in the RNA strand.

The substitution of a purine for a pyrimidine, or vice versa, is called a transversion. The substitution of one purine for another or one pyrimidine for another is called a transition. Either of these can be referred to as a point mutation, but transversion is the most specific answer to this question.

Nucleic acids are made up of nitrogenous bases and a sugar-phosphate backbone. The sugar will vary depending on if it is an RNA or DNA molecule that's being discussed. RNA has ribose while DNA has deoxyribose. The nitrogenous bases are guanine, adenine, thymine, cytosine and uracil. Tyrosine is an amino acid, therefore not involved in the composition of nucleic acids.

Chromosomal related mutations include deletion, duplication, inversion, or translocation. Nondisjunction is a faulty separation event of homologous chromosomes but does not necessarily involve improper chromosome structures. Independent assortment is a mendelian inheritance principle which states chromosomes are divided randomly into two daughter cells. Synapsis is a normal pairing up event of homologous chromosomes in prophase I. Polyploidy is a condition of having more than two sets of chromosomes and is typically a characteristic of a species, not an abnormality.

The three major components of a nucleotide in DNA are phosphate, deoxyribose, and one of the four nitrogenous bases. The phosphate and deoxyribose alternate along the backbone, and the nitrogenous base codes for the type of protein made in transcription and translation.

In the DNA strand, adenine bonds to thymine. It does not bond to the other bases in DNA. In RNA, adenine bonds to uracil.

In the DNA strand, guanine bonds to cytosine. It does not bond to the other nitrogenous bases. Guanine and cytosine form three hydrogen bonds to keep complementary strands of DNA together.

Shine-Delgarno sequences are ribosomal binding sites slightly upstream of start codons on prokaryotic mRNA. Eukaryotic mRNA is more complicated (it does not contain Shine-Delgarno sequences) and contains promoter regions that are responsible for recruiting translation factors and ribosomal subunits.

One of the primary differences between purines and pyrimidines is that purines consist of two rings, whereas the pyrimidines consist of one ring. One way to help remember the differences between purines and pyrimidines is that pyrimidines are like pyramids: sharp. Sharp things CUT (Cytosine Uracil Thymine). Note that uracil is only present in RNA, while thymine is only present in DNA. All nitrogenous bases bond to the sugar in the DNA backbone. The sugar is also connected to a phosphate group via a phosphodiester bond.

Purines are adenine and guanine, while pyrimidines are cytosine, thymine, and uracil.

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.