A reading frame is a sequence of genetic information which contains data which can be used to code amino acids which can be joined together in polypeptide chains to create proteins. Reading frames are found in both DNA and RNA. Researchers can study reading frames to learn more about specific genes and about the processes which can interfere with gene expression.
In the case of DNA, DNA contains sets of nucleotides known as triplets or codons. Each codon can be transcribed by RNA into another triplet, and in turn translated into an amino acid. This system is used by every living organism on Earth to encode genetic information. The organism's genome, the complete collection of genetic information it contains, contains instructions for everything from how many limbs to grow in utero, in the case of mammals, to blueprints which can be used to replace cells as they die.
The reading frame is the section of DNA or RNA which contains directions for making a complete protein. In DNA, there are six potential reading frames, because the start of a reading frame depends on where one starts reading, and DNA is double stranded. With RNA, there are three potential reading frames. It is important to identify the right start point, as otherwise the reading frame will transcribe and translate as gibberish. By looking at a reading frame, a researcher can see which protein is supposed to be encoded by the group of codons.
As one might imagine, inserting or deleting codons presents a problem. Just as one becomes confused when reading a book with a page yanked out or a random paragraph inserted, the expression of genetic information becomes confused when a reading frame is altered. As a result, a gene may not express as expected, and people may develop congenital abnormalities. This is one way in which people can experience genetic abnormalities.
In an open reading frame, clear start and stop codons can be identified. An open reading frame may contain a complete gene, or overlapping genes; the genetic code is not always as tidy as one might imagine. In fact, the genetic code contains a lot of what is known as noncoding DNA, meaning that the DNA does not appear to serve a function in terms of gene expression. Noncoding DNA can contain interesting information about the genetic inheritance of a species, and may serve other functions which will be discovered over time as researchers learn more about the genome.
By Mary McMahon
Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a All The Science researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.