Thursday, April 9, 2009

"Immortal"

What are immortal genes? What are some reasons why there may be genes that can stay the same for a long period of time? What are some functions of immortal genes? Why have these specific functions stayed the same over time? When the species differ how do the genes stay the same?
Posted by at

3 comments:

  1. Amie KimApril 9, 2009 at 9:02 PM

    Immortal genes are genes present in organisms that have been maintained throughout evolution. There are about 500 genes that exist in all domains of life (Carroll 79). These immortal genes withstood more than 2 billion years of mutation and most maintain the gene expression of these immortal genes.
    These immortal genes do not disappear, because they are fundamental in the survival of the organisms by functioning in decoding of DNA and RNA, and making of proteins. All living cells have genetic materials that have to be translated and transcribed to produce proteins such as enzymes. Since all organisms need gene expression to survive, the fundamental genes that are involved in gene expression are preserved and do not become mutated and become a selective disadvantage leading to the fossilization of the genes. Since these genes are essential to all species, natural selection constantly selects against the mutations and prevents the fossilization of the genes.
    Immortal genes such as the triplets that code for the 12 essential amino acids have stayed alive for billions of years. The 12 essential amino acids are used by all organisms and even though the specific sequence of the gene triplets may differ, the coding of the triplets result in the same amino acids. These functions have stayed the same over time, because the common ancestors of species today had the gene to code for the amino acids and other essential genes in survival and natural selection did not affect it. Since the coding of the 12 essential amino acids and the necessity of the amino acids in the production of enzymes, tissues, antibodies, and more have not changed over time, the genes became immortal. Even as other genetic mutations occurred and organisms diverted from a common ancestor through random mutations, selective advantages, and time, these new species, nonetheless, needed the same amino acids to develop vital enzymes and other products for the organism. Random mutations that do change the immortal genes are constantly selected against to maintain the essential genes crucial for organisms’ survivals. These immortal genes could change if the random mutation can cause a selective advantage or maybe create a new amino acid, but this has not been the case throughout evolution, and thus resulted in the maintenance of the approximately 500 genes shared throughout all living species. These genes in humans may be protected from being destroyed by having telomeres at the end of the chromosomes of the nucleotide sequence TTAGGG repeated about 100 to 1000 times to prevent the genes from eroding away (Campbell 300). Also, the vast number of introns and noncoding nucleotide sequences decrease the chance of mutations in the exons, further preventing the fossilization of immortal genes.

    ReplyDelete
  2. Mark LeeApril 11, 2009 at 10:15 AM

    Immortal genes are sequences in DNA that do not change over time, and therefore are very similar between different phyla and classes. Immortal genes do not escape mutation, they mutate as frequently as any other gene, but because immortal genes consist of a core set of genes necessary for life, any extensive mutations are sure to cause death. Therefore while individuals may have mutations in these genes, these individuals will not survive to reproduce, and there fore the gene will persist on the whole. It is important to note however that in immortal genes, individual nucleotides may vary due to mutations, but when these mutations do not affect the function of the gene they are allowed to persist. This results in immortal genes having some areas in witch they vary from species to species, but on the whole the genes remain remarkably similar between all organisms. The genes stay the same even when the species differ because immortal genes serve to accomplish functions that are the basis for cellular life. Therefore these genes are a necessity for all living beings.

    One example of an immortal gene is DNA polymerase. Necessary for all life forms to propagate, it is a common gene across all species. Another example would be the genes coding for the formation of the lipid bi layer plasma membrane. Once again this is a structure that all cells rely on. Therefore, natural selection does not allow for excessive change to that gene. There are some cell types that have differing types of cell membranes, but all types of cell membranes are built around the plasma membrane, so the genes coding for the plasma membrane can be still said to be immortal. Many of the other genes involved in making proteins that are involved in DNA replication can also be cited as immortal genes.

    http://en.wikipedia.org/wiki/DNA_polymerase
    http://en.wikipedia.org/wiki/Cell_membrane

    ReplyDelete
  3. Juliya KulbachenkoApril 13, 2009 at 7:40 PM

    Immortal genes are “key pieces of evidence for the descent of all living species from common ancestors” (36. They also provide a new means of reconstructing early events in life’s evolution. These immortal genes were able to endure over millions of years, against mutations that could have erased and altered it. When scientists find these immortal genes they are able to get a clue of what the past was like. They are clues to the history of life’s evolution.

    Immortal genes are powerful evidence to “natural selection …and the descent of life from common ancestors” (72). When looking at 2 billion year old archaean genes scientists found that they revealed a lot about our won eukaryotic ancestors. There are DNA codes in these archaean organisms that also exist in human DNA. This evidence shows archaean was one of our original genetic parents. The immortal genes function is to help people learn more about their past and relate back to our ancestors. They tell us how organisms evolved and what connections each species have with one another.

    http://scienceblogs.com/gnxp/2009/01/and_then_there_was_bernie.php

    ReplyDelete

Subscribe to: Post Comments (Atom)