"Survival of the Sickest" Chapter 6, Summary

This chapter started off by talking about how the first vaccine was the cowpox infection because it resulted in protection from smallpox. It turns out the word "vaccine" actually comes from the Latin word "vacca," and now suddenly everything makes sense! The chapter went on to talk about "junk DNA," which is 97% of the DNA in your body that, according to early scientists, don't do anything. That means that only 3% of your DNA contains instructions for building cells. We later learn that "junk DNA" isn't so junk after all. The chapter also mentions that a third of your DNA is derived from viruses. It is also brought up that humans have a total of approximately 25,000 genes. A man, Jean-Baptiste Lamark, was also mentioned. He was wrongfully accused of coming up with the theory of inherited acquired traits. This means that whatever traits a parent develops during his life will be passed on to his/her child. This theory, though not exactly right, isn't exactly wrong either. The rest of this chapter mainly talks about Barbara McClintock's evidence for "jumping genes." "Jumping genes," also known as transposons, are whole DNA sequences that move from one place to another when under environmental stress. Transposons act like "copy and paste," inserting themselves into genomes while still remaining in the same location. These "jumping genes" make up a large portion of our "junk DNA." Lastly, this chapter talks about RNA. Retroviruses are made up of RNA, an example being HIV. Using an enzyme called reverse transcriptase, retroviruses can transcribe themselves from RNA to DNA. The retroviruses that are a part of our DNA are called HERVs. They are believed to play a number of roles in human health.