Shubin ponders "What if you could do an experiment in which you treated the embryo of a fish with various chemicals and actually changed its body, making part of its fin look like a hand? What if you could show that the genes that build a fish's fin are virtually the same as those that build our hands?" on pg. 45. And later (on pg. 56) he states that the Sonic the Hedgehog gene in skates, chickens, and humans are virtually identical. This reminds me of he idea of putting different genes with specific traits into another species. (Like when we inserted jellyfish glow genes into E. Coli!) So, if the genetic code is compatible across the boards, at what point, how much of one's organisms genes has to be inserted another for the two different species to be able to reproduce with one another? Or would it always be impossible (based on the number of chromosomes in one species vs. another? And would this be considered convergent evolution?
(Jackie Edelson, jedelson92@gmail.com)
There is a major issue that many people fail to recognize about the genomes of all species :"data from diverse eukaryotic lineages reveal extensive intra- and interspecific variation in genome content." (Parfrey, 2008). We were tought in the genetics unit that members in the same species, such as two humans, have genomes that are almost 99% identical, leading us to believe that all eukaryotes are not that different afterall. This leads us to make the quick generalization that all species "share nearly identical genomes and genomic integrity is maintained through the cell cycle." (Parfrey, 2008). However, through studies of numerous genomic lineages, significant variation was revealed to exist throughout organismal life cycles and among members of a single species at a scope much larger than previously thought. This makes the phenomenon of evolution a much more dynamic force than anyone could have imaged.
ReplyDeleteAlmost all scientists hold true to the concept that "the diversity of genomic processes have similarities that suggest an ancient origin of the basic features of the genome propagation including meiosis and mitosis." However, what many fail to realize is that two significant forces are at play that affect variation in DNA: "maintainance of the integrity of genetic material for transmission to future generations, and allowing extensive variation within life cycles and among conspecific individuals." (Parfrey, 2008). Diversity is incredibly important for the expression of different traits to adapt to life on Earth, but at what point do species become so different that they can no longer maintain the integrity of genetic material and cannot procreate? A shocking finding was made in studying the difference in human DNA sequences in which "insertions and deletions of kilobase to megabase segments of DNA that lead to polymorphisms in the presence/absence of chromosome regions and genes contained within them. The scale of this variation is enormous; a survey of 270 individuals found that 360 MB (13% of the genome) varied, presenting a marked contrast to the genomic conservation symbolized by the 99% similarity in orthologous sequences between humans and chimps." (Parfrey, 2008). With DNA in the same species being able to vary so much, it is no surprise that such vast levels of variation could exist in even greater amounts across other species.
To answer Jackie's question, an estimate amount of similarity between genetic codes seems to need to be at least 87% before they can produce viable offspring, assuming that they have a similar number of base pairs in their genetic code. There are also huge differences in the number of base pairs among members of different species: "researchers reported that a species of Italian bat, Miniopterus, has a genome half the size of the human genome." (Winstead, 2001). I disagree with Jackie's statement that genetic codes are compatible across different species because so much variation exists even in between members of the same species, and it would surely impossible to create a viable species by artificially modifying two different species to make a single one. Yes, a single gene, such as the jellyfish glow gene, can be inserted into E. Coli and expressed, but bacteria are a unique instance because they are very simple organisms who do not revise their DNA for corrections. Therefore, the natural process of evolution by the expression of inherited traits cannot be modified to converge new species, only to make new ones.
http://www.genomenewsnetwork.org/articles/02_01/Sizing_genomes.shtml
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2933061/?tool=pmcentrez
Troy Glickstern
cleverstar8@comcast.net