All of these are actual nucleic acids, except xDNA, which does not exist. Therefore, we can eliminate this answer right away. mtDNA, or mitochondrial DNA, is a small portion of a person's DNA that is housed within the mitochondria. It is significant in that it is inherited solely from the mother and is thought to have evolved separately from "normal" DNA; however, it isn't involved with amino acids at all, so it too can be eliminated as a choice.

RNA (ribonucleic acid) is heavily involved in protein synthesis (the creation of new proteins, which are just long chains of amino acids). The first part of the process is transcription, in which the double-stranded DNA (deoxyribonucleic acid) is "unzipped" by the enzyme helicase. Another enzyme, RNA polymerase, "reads" this single strand and produces a chain of nucleotides exactly opposite to the DNA's nucleotides, and this chain, in its mature form, is called mRNA (messenger RNA). Living up to its name, mRNA travels outside the nucleus, where DNA is housed, and out into the rest of the cell, to the ribosome.

At this point, translation begins. Every trio of nucleotides on the mRNA, called a codon, represents a specific amino acid. Another type of RNA, tRNA (transfer RNA) can "translate" the codon into the appropriate amino acid, since it carries a three-nucleotide-long anticodon on one segment, which can form a bond with the corresponding codon on the mRNA, and an amino acid on the other segment. In this way tRNA brings amino acids to the growing protein chain. Another involved nucleic acid is rRNA (ribosomal RNA) which makes up a large part of the ribosome itself and is responsible for helping to properly attach each amino acid that the tRNA brings to the amino acid sequence being built.

Based on the question, which asks you to identify the nucleic acid that helps carry the protein "message" from the nucleus to the ribosome, the correct answer is mRNA.

In DNA transcription and translation, the start codon is the first codon, among those transcribed into the mRNA sequence, that is translated during protein synthesis. In humans, this is always AUG, which codes for the amino acid methionine.

Of the other answer choices, three function as a stop codon: UAA, UGA, and UAG. The other choice, CUG, codes for the amino acid leucine.

A mnemonic for remembering that AUG is the start codon is to make the connection that the school year typically starts in August.

According to Chargoff's rules, we know that the ratios of Adenine:Thymine and Guanine: Cytosine will be approximately 1:1. Once you know that the percentage of Adenine is 18%, you can multiply by two to find the total percentage of Thymine and Adenine (36%), then, you can subtract that number from 100% to find the percentage of Cytosine and Guanine - 64% (because the total percentage has to equal 100%), finally you can divide it in half to get the percentage of Guanine bases (32%).

Because of the presence of Deoxyribose sugar, you know that the genome is composed of DNA. Only RNA contains Uracil bases, so the answer is 0%.

Every nucleic acid is made up of 3 parts — a pentose (5 membered ring) sugar, a phosphate group and a nitrogenous base. 

A hexose sugar has a six membered ring. Ribose and deoxyribose are types of sugars found in nucleic acids, but are only found in RNA and DNA respectively.

While DNA is usually found double stranded and RNA is often found single stranded, RNA can also be found in double stranded forms, notably in viruses. 

Adenine and Guanine are purines and consist of two connected nitrogenous rings. Cytosine, Uracil, And Thymine are pyrimidines and consist of one nitrogenous rings.

One can remember this by remembering that stones had to be CUT in order to build the PYRAMIDs.

The aromatic nitrogenous bases absorb UV radiation, which allow nucleic acids to be detected by UV absorbance.

Nucleosides have only a nitrogenous base attached to the sugar. Nucleotides have a phosphate group and a nitrogenous base attached to the sugar. An easy way to remember this is that nucleoSides have a single group attached to the sugar, and nucleoTides have two groups attached to the sugar.

Using Chargoff's rules, one can calculate that Virus A has 64% C-G pairs in its genome and Virus B has 50% C-G base pairs in its genome. Since C-G pairs have an additional hydrogen bond, they are more stable than A-G pairs, so more energy will be required to separate the strands and "melt" the DNA. Since the two genomes are the same length, the stacking effects will be the same, so the deciding factor will be base pair composition, and Virus A's genome will have a higher melting temperature.