Nucleic Acids- Properties of RNA

What is RNA and where would you find it in a cell?

RNA is ribonucleic acid. It is like DNA, but with an -OH group on the 2' carbon. RNA is found inside the nucleus as well as in the cytoplasm. There are many different types of RNA that all achieve different functions in the cell.

What are the similarities between DNA and RNA (chemically, structurally)?

DNA and RNA are both made up of long chains of nucleotides. They are both read from the 5' to 3' end. Both DNA and RNA contain adenine, cytosine and guanine.

What are the differences between DNA and RNA (chemically, structurally)?

DNA is double-stranded, whereas RNA is single-stranded. As alluded to earlier, DNA has deoxyribose sugar, whereas RNA has ribose sugar, the latter of which has an extra -OH on the 2' carbon. While DNA is usually present as a double helix, RNA can take on a variety of structures and forms due to intrastrand base pairing (i.e. pairing between bases of the same strand). DNA has the base thymine, while RNA has the base uracil instead. Another difference between the two is that RNA has a lower viscosity (resistance to flow- i.e. it's more watery) than DNA due to only being single-stranded.

What are the standard base pairing rules for RNA?

Adenine pairs with uracil, whereas cytosine pairs with guanine.

Why does RNA have ribose, not deoxyribose?

I'm not sure about this. I read somewhere that RNA may have been the first nucleic acid to form, though. I wonder whether DNA later became preferred for information storage due to its greater stability (lacking the 2'-OH group means that it has one less place where it can react with other molecules). Since RNA is not used as much for information storage, it probably faced far fewer selection pressures.

(Of course that might just all be complete gobbledegook. Accept this explanation at your own peril.)

What are introns and exons?

Exons are the parts of the gene that code for amino acids, whereas introns are non-coding parts that are normally spliced out during mRNA processing.

What are the functions of the various RNAs?

There are many different types of RNA in the cell, all with different functions. There are also many types of RNAs whose functions we have not yet quite determined.

• mRNA (messenger RNA)- carries genetic information from the DNA in the nucleus to ribosomes in the cytosol and ER.
• tRNA (transfer RNA)- carries amino acids from the cytosol to the ribosomes, where mRNA is being translated.
• rRNA (ribosomal RNA)- these are components of ribosomes.
• snRNA (small nuclear RNA)- process RNA transcripts.
• siRNA (small interfering RNA)- also known as "silencing RNA" as they can silence certain transcripts.
• miRNA (micro RNA)- can cause degradation or block translation of RNA.