Summary of "Survival of the Sickest" Chapter 6

  The Chapter 6 of "Survival of the Sickest" starts off with the origin of vaccination. The vaccine came from the Latin word of "cowpox" which is an infection that can used against smallpox. Soon after, the author begins to talk about genes. The genes of a person are organized in 23 pairs of chromosomes, one set of 23 chromosomes came from the mother, and the other set came from the father. However, less than 3% of the DNA are about instructions of building cells, and scientists decided to call the other 97% the noncoding DNA instead of "junk DNA" because the fact that they are only not directly involved with creating proteins doesn't make the 97% useless. Also, the author noted an interesting fact that the mitochondria (the power plant of a cell) was once a bacteria that lived along with humans. 
  Later on, the author switches the topic to mutations. The genetic changes occur not only when there are errors in the transport of genetic data between generations, but also when organisms are exposed radiation or powerful chemicals. Outbreaks and pandemics are caused by either antegenic drift (when a mutation occurs in DNA of a virus), or antigenic shift (when a virus acquires new genes from a related strain).
  And finally, another topic the author mentioned was the "jumping gene". When the organisms are under extreme outside conditions, a sequence of DNA "copy and paste" themselves from one place to another, insert themselves into active genes and affect nearby genes by changing the entire sequence. This mutation is called "Jumping genes", and it was discovered by Barbara McClintock. There are two types of "jumping genes"- the first is DNA transposons, which jump through a cut-and-paste process; the second type is called DNA retrotransposons, which goes through a copy-and-paste process. Especially, the transposon is a huge part of our noncoding DNA, or "junk DNA".

- Andy Liu '15