On pages 137-140, Moalem describes the genetic nomads
“jumping genes” and how they have reshaped the understanding of mutation and
evolution. Jumping genes are also known as tranposons. They either copy and
paste themselves or they cut and paste themselves. The Jumping genes can create
a great difference as shown with the fruit flies. The jumping genes are said to
be responses to internal or environmental stress and as a result the jumping
genes create mutations in the genome. This relates to Big Idea 3, Living
systems store, retrieve, transmit and respond to information essential to life
processes because jumping genes create mutations in the genetic material.
On page 150, Moalem says there are two types of jumping
genes. What are the two types of jumping genes? Describe the two types. Give an
example of one of the types, explain the mutation then relate the significance
of the mutation to evolution.
(Hervy Ong, hong3@students.d125.org)
On page 150, Moalem describes the two types of jumping genes as DNA transposons and retrotransposons. According to Moalem, the DNA transposons follow a "cut-and-paste process" where they cut themselves and paste themselves at a different part of the genome (Moalem 150). The retrotransposons are "copy-and-paste jumpers" that copy themselves and are pasted into a new section, so two of copies of the gene exist in the genome (150). The retrotransposon specifically "copies itself onto RNA" then moves to the part of the genome it wants to insert itself into and then "uses reverse transcriptase to paste itself into the DNA" (150). In the article "DNA Transposons: Nature and Applications in Genomics" by Muñoz-López and García-Pérez, DNA transposons have a transposase gene that is surrounded by Terminal Inverted Repeats (TIRs) (Muñoz-López and García-Pérez). The DNA transposon moves itself through a process where the "transposase recognizes these TIRs to perform the excision of the transposon DNA body, which is inserted into a new genomic location" (Muñoz-López and García-Pérez).
ReplyDeleteIn the article "Transposons, or Jumping Genes: Not Junk DNA?," Penissi states "transposons are highly conserved among distantly related taxonomic groups, suggesting that they must be of some biological value to the genome" (cited in Pray). This means that the same transposons, or transposable elements, "exist in genomes of distantly related species, such as fish and frogs" (Pray). This would relate to Big Idea 1, the process of evolution drives the diversity and unity of life, by showing the universality of DNA because very different species have similar retrotransposons which suggests a common ancestor. Bejerano et al. have discovered a family of retrotransposons in Latimeria menadoensis called LF-SINE which regulated the expression of Isl1 gene in that species (cited in Pray). The LF-SINE family is found in many species like " frogs, chickens, opossums, dogs, rats, mice, chimps, and humans" which once again suggests a universality in genomes (cited in Pray). Being a retrotransposon, a LF-SINE TE copies itself and pastes itself somewhere else in a person's genome. In this case, "a 200-base-pair LF-SINE [was found] some 500,000 bases away from the Isl1 gene" (cited in Pray). This family of retrotransposons not only shows a unity in all species due to evolution, but the family shows the possibility of using retrotransposons to regulate gene expression. According to Moalem, "McClintock believed that the jumps are a genomic response to internal or environmental stress" (Moalem 138-139). This suggests that jumping genes can be activated by changing the species' environment. In the future, scientists may be able to influence jumping genes by changing a species' environment to turn off a potentially harmful gene and cause a beneficial mutation which would influence the species' evolution. This regulation would relate to Big Idea 3: living systems store, retrieve, transmit and respond to information essential to life processes, because the scientists would be changing the way the species receives information by mutating its genes.
DNA Transposons: Nature and Applications in Genomics:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2874221/#R51
Transposons, or Jumping Genes: Not Junk DNA?:
http://www.nature.com/scitable/topicpage/transposons-or-jumping-genes-not-junk-dna-1211
(Name: Will Han email: wihan4@students.d125.org)