RNA Structure and Function

There are two antiparallel strands of DNA so that the five-prime end of one strand will face the three-prime end of another strand. Remember, the three-prime end has the free hydroxyl group and the five-prime end has the free phosphate group. The outside of the double helix has the deoxyribose molecule and the phosphodiester bond, while the inside of the double helix has the nitrogenous bases that connect to one another through hydrogen bonding. There are ten bases per turn of the helix. There are major grooves and minor grooves that are made from the asymmetry between the base pairs.

The fact that thymine goes together with adenine and that guanine goes together with cytosine means that these are considered complementary base pairs and matches completely with Chargaff’s rule. Some complementary base pairs, namely A and T, have two hydrogen bonds, while C and G have three hydrogen bonds between the two molecules.

The strands will separate at higher temperatures and in the presence of certain chemicals. This is called denaturing the DNA. The single strands of DNA can be put together again if the circumstances are right. Because of the differences in the number of hydrogen bonds, the DNA with high GC content is harder to break than those that are high in AT.

DNA will store the genetic material of the cell. With vertical gene transfer, the mother cell transfers the genetic material to the daughter cells. DNA is replicated anytime the cell divides to make daughter cells. This is basically the only function that DNA has with regard to the cell. There are no structural elements to the DNA molecule.

RNA STRUCTURE AND FUNCTION

Ribonucleic acid or RNA is very similar to DNA but it is generally single-stranded, has much shorter strands, and contains ribose instead of deoxyribose. RNA is made from ribonucleotides and is linked together via phosphodiester bonds, just as is seen in DNA. The nitrogenous bases are different with RNA. There is adenine, guanine, and cytosine like in DNA but the uracil replaces thymine that is seen in DNA. DNA is somewhat more stable than RNA so it is better than RNA in keeping genetic information. Adenine matches with uracil in the RNA molecule.

The main function of RNA is to help turn the DNA message into the different proteins. There are several kinds of RNA, including messenger RNA, ribosomal RNA, transfer RNA, and small nuclear RNA. Messenger RNA takes the DNA code and sends it to the ribosomes, where it is read. Transfer RNA contains the amino acids that combine to make proteins. Ribosomal RNA is part of the structure of the ribosome. Small nuclear RNA is only seen in eukaryotes.

There is a transcription process, in which DNA information gets transferred to messenger RNA through the activity of RNA polymerase. Then, the messenger RNA exits the nucleus or travels away from the DNA in order to go to the ribosomes. At the ribosomes, transfer RNA contains a single amino acid per molecule. The message is read in the ribosomes and the protein strand is added one amino acid at a time by transfer RNA. Messenger RNA is an unstable molecule that is easily degraded if protein is not made relatively quickly.

Ribosomal RNA and transfer RNA are much more stable than messenger RNA. These are made by DNA and then cut to smaller segments. The nucleolus is where ribosomal RNA processing takes place in eukaryotes but this happens in the cytoplasm of prokaryotes.

Ribosomal RNA makes up about sixty percent of the ribosome and this is where the messenger RNA ultimately binds. Ribosomal RNA makes sure that the transfer RNA and messenger RNA are aligned correctly. Ribosomal RNA is the only RNA type that has enzymatic activity, called peptidyl transferase, which helps to make the peptide bond when proteins are made.

Transfer RNA is very short and has only 70 to 90 nucleotides per molecule. Each one carries an amino acid that can be inserted into the polypeptide molecule. While it is small, it is essential to the making of proteins so mutations in the making of this RNA type can affect protein synthesis to a great degree.

Remember that DNA is the hereditary material in cells but RNA can serve as the genetic information source in the virus particle. In viruses, RNA can be single-stranded or double-stranded. As mentioned, certain RNA types in the virus can be directly