Sunday, March 15, 2009
DNA decay
Throughout this novel, Carroll talks about nucleotides decaying from the genome, and how this process is a result of the specific nucleotides losing importance in the genome as a whole. However, Carroll neglects to go into detail about this "DNA decay". Describe the process of "DNA decay" in depth and explain how this can attribute to mutations in the genes of that organism.
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DNA decay is an extremely loose term. Generally, it means the change, alteration, or loss of a series of nucleotides within a cell’s genetic information. DNA damage can be do to environmental factors, and normal metabolic processes inside the cell. It is said that this damage occurs at a rate of 1.000-1million molecular lesions per cell per day. So in fact, “DNA decay” is happening all of the time. However, that does not mean that the human genome is in jeopardy. Most DNA damage affects only the primary structure of the double helix, where the base pairs themselves are chemically changed. This can cause DNA loss because a change in the nucleotide sequence can effect the coiling of the DNA, which changes the structure of the double helix complex. Through either endogenous cellular processes (oxidation, alkylation, hydrolysis), exogenous (uv rays and radiation) or simply a genetic defect or change in the composition, DNA decay can occur. Mutations then arise, and the structure, function, or internal/external processes of that cell can be altered, causing a mutation.
ReplyDeleteAs Melissa said, DNA decay generally refers the change, alteration, or loss of a series of nucleotides within a cell’s genetic information. DNA decay can refer to numerous things such as a change in the regulatory genes in which the genetic code is read, or a change in the code itself where a nucleotide is inserted, deleted, or substituted to create a whole new line of code. Decay has a rather negative ring to it. Where sometimes the decay could lead to a biological advancement to become a selective advantage helping the creature survive and reproduce. These mutations could affect the creature’s structure or function in order to help it live with the behavioral adaptations that they acquired.
ReplyDeleteFor example, the owl monkey who has adapted the nocturnal life has also adapted the fossilization of the opsin gene, which could be a form of DNA decay. First of all the genetic gene was “decayed” or fossilized by the regulatory with the a simple genetic code substitution when the code of TGG turned into a TGA which became a terminating code of the RNA polymerase to stop transcribing which thus leads to a shortened mRNA which affects the translation of the genetic code into a protein. With this deprived code in the protein building process, it led to the deprivation of color distinction in owl monkeys. This deprivation became more of a selective advantage which helps them seek out food and avoid predators in the dark because of black and white vision.
So the DNA decay could be a substitution in the genetic code which could lead to the end of transcription for an entire genetic sequence. Cutting out certain codes that used to be functional but have now become “decayed.” Other DNA decay that doesn’t exactly affect the transcription and translation of the genetic code into proteins which later affect a species function and structure is the destruction of the telomere.
The telomere is repetitive DNA sequences located at the termini of linear chromosomes of most eukaryotic organisms, and a few Prokaryotes. This protects from possible DNA decay at the ends of the sequence which prevents the mutation of function. The shortening of telomeres is most closely related to aging because of the end replication problem that is exhibited during DNA replication in eukaryotes only. This is exhibited by whitening of hair as the DNA code begins to shorten and the DNA code actually loses information and code at the ends.