Monday, November 1, 2010

More About Frames

I must have been tired last night when I put up my post on reading frames. One thing that I have quickly realized is that writing about scientific topics is very difficult to do well. Biology is a field with a great deal of detail, and everything is interconnected. Where do I start when I talk about transcription and translation? The definition of a nucleus? What a ribosome is? You see my problem.

I think that it may well be easist to provide further reading suggestions from Bioweb or various other sources and simply discuss the topic that I am interested in discussing, rather than starting at the very beginning.

With that in mind, I began learning about reading frames when we were talking about hypervariability in B- and T-cell receptors. These hypervarible loops on the receptor surface allow for an enormous diversity in the ability of these cells to detect antigens. What is amazing to me is that we have a codified system within our genome, expressed by parts of our immune system, that actually allows for the limited re-writing of the genome. This further allows for a limited restructuring and variability of the proteins on the cell receptor surface. What results is our ability to detect and build immune responses to each type of immune invader. The picture is a bit larger than that, but maybe I'll do a series on immunology.

One possible course of study for grad school is the plasticity of genes expressed by organisms that survive attempted killing by antibiotics and how these genes allow them to evade the defense mechanisms of the host. Understanding like this can help us develop more effective vaccines and more promising antibiotics. Antibiotic resistance is a huge problem in the medical field, and a mechanism that allows us to completely bypass an organism's ability to build resistance would be ideal. Currently we have discarded early versions of some antibiotics simply because we have better synthetic ones that don't have the track record of increasing resistances.

Mutations resulting from the misreading of reading frames are fascinating to me, because so much is dependent on how the nucleotide sequence is "read" and where the starting points are. Misreading the sequence or copying errors like adding or deleting a nucleotide can have devastating effects on the organism or none at all. Frameshifts are particularly interesting to me, because they can be lethal or produce high morbidity in nature. They involve deletions or insertions of nucleotides that throws off the reading frame (Remember, the frame is the group of codons that codes for a protein, and codons are triplets of nucleotides. I think I was off in my previous definition) and so there is either one too many nucleotides or an extra one. While the code is very redundant (there are 64 codons for 20 amino acids) if the frame is thrown off the stop codon will not be read properly, and then all kinds of havoc will ensue.

Further Reading: Immunology: Hypervariable Loops
Cell Biology: Reading Frames and Frameshift Mutations

No comments:

Post a Comment