DNA encodes all genetic information, and is the blueprint from which all biological life is created. In the long-term, DNA is a storage device, a biological flash drive that allows the blueprint of life to be passed between generations 2. RNA functions as the reader that decodes this flash drive. This reading process is multi-step and there are specialized RNAs for each of these steps.
Below, we look in more detail at the three most important types of RNA. The nitrogen bases in DNA are the basic units of genetic code, and their correct ordering and pairing is essential to biological function. The four bases that make up this code are adenine A , thymine T , guanine G and cytosine C. Bases pair off together in a double helix structure, these pairs being A and T, and C and G. RNA molecules, by comparison, are much shorter 3. Eukaryotic cells, including all animal and plant cells, house the great majority of their DNA in the nucleus, where it exists in a tightly compressed form, called a chromosome 4.
This squeezed format means the DNA can be easily stored and transferred. In addition to nuclear DNA, some DNA is present in energy-producing mitochondria, small organelles found free-floating in the cytoplasm, the area of the cell outside the nucleus.
The three types of RNA are found in different locations. If it receives the correct signal from the ribosome, it will then hunt down amino acid subunits in the cytoplasm and bring them to the ribosome to be built into proteins 5.
This page has been archived and is no longer updated. Ribonucleic acid RNA is a linear molecule composed of four types of smaller molecules called ribonucleotide bases: adenine A , cytosine C , guanine G , and uracil U. RNA is often compared to a copy from a reference book, or a template, because it carries the same information as its DNA template but is not used for long-term storage. Each ribonucleotide base consists of a ribose sugar, a phosphate group, and a nitrogenous base.
It carries the correct amino acid to the site of protein synthesis in the ribosome. It is the base pairing between the tRNA and mRNA that allows for the correct amino acid to be inserted in the polypeptide chain being synthesized Figure 4. Any mutations in the tRNA or rRNA can result in global problems for the cell because both are necessary for proper protein synthesis Table 1. Figure 4. A tRNA molecule is a single-stranded molecule that exhibits significant intracellular base pairing, giving it its characteristic three-dimensional shape.
Thus, RNA clearly does have the additional capacity to serve as genetic information. Although RNA is typically single stranded within cells, there is significant diversity in viruses. Rhinoviruses, which cause the common cold; influenza viruses; and the Ebola virus are single-stranded RNA viruses. Rotaviruses, which cause severe gastroenteritis in children and other immunocompromised individuals, are examples of double-stranded RNA viruses.
Because double-stranded RNA is uncommon in eukaryotic cells, its presence serves as an indicator of viral infection. A nucleic acid is purified from a mixture. The molecules are relatively small, contain uracil, and most are covalently bound to an amino acid.
Which of the following was purified? Skip to main content. Biochemistry of the Genome. Search for:. Think about It What are the functions of the three major types of RNA molecules involved in protein synthesis? Key Concepts and Summary Ribonucleic acid RNA is typically single stranded and contains ribose as its pentose sugar and the pyrimidine uracil instead of thymine.
An RNA strand can undergo significant intramolecular base pairing to take on a three-dimensional structure.
0コメント