Survival of the Sickest Chapter 6 Summary

     In chapter 6, Dr. Edward Jenner discovers that the people infected with cowpox are immune to smallpox. To test his findings, he infected a bunch of young men with the cowpox disease, and the results led to the eventual creation of vaccines. The chapter built off of this and began talking about how genes are able to change, and how they can form antibodies to fight against infections. It mentioned that humans have 23 pairs of chromosomes, and that the 23rd one is the sex chromosome which determines whether you will be a boy or a girl. When the sperm from the dad and the egg from the mom are brought together, the form a single cell known as a zygote. 

Zygote Cell

X and Y Chromosomes

     Interestingly, only 3% of our DNA is actually used for coding, and the rest is "junk DNA", which would later be called non-coding DNA. Regarding mitochondria, this chapter mentioned that it produces energy that is needed for the cells to run, and the chapter talked about how mitochondria was likely a separate bacteria, but now lives in our cells. Surprisingly, scientist believe that 1/3 of our DNA may be from viruses.

Previous view of Noncoding DNA 

"Junk DNA" later is discovered to
act as "jumping genes".

     We reviewed that a mutation occurs when the DNA is copied incorrectly, but in this chapter, we learned about mutations caused by radiation, chemicals, or the Sun. Speaking of the sun, we learned that outbreaks of diseases are likely related with the Solar Flares/Sunspot Peaks that occur every 11 years. 

Mutations caused from radiation

 

     We learned how Lamarch was thought to be the man responsible for the creating the theory of inherited acquired traits, which would mean that traits gained throughout one's lifetime would be found in in the future generations. In some support of this theory, Barbara McClintock discovered "jumping genes", or transposons, which are genes that will move from one place to another under stressed conditions. She believed that they jumped to specific locations, toward the genes that would cause the most beneficial possible mutation. Cairns, another scientist, believed that the conditions just caused the mutations to go faster, not jump around. This increase in mutation speed is known today as hypermutation, and it occurs at up to 100,000,000 x faster than the regular mutation.

"Jumping Genes"

Environmental Affect

     Chapter 6 taught us about the Weismann barrier, which prevents mutations, and any information at all, from passing from somatic cells to germ cells. However, it does allow some viruses to pass through. We learned that some cancer is hereditary, and some is by external triggers such as smoking and radiation. 

External cause of cancer

     Connecting everything in the end, we found that "jumping genes" are involved in the producing of antibodies, a large part of Junk DNA is made of "jumping genes" and viruses, and building up anything in your body involves going from DNA to RNA to protein. 

Antibodies

     We also learned that retroviruses are made of RNA, and they can change your DNA, because they go from RNA to DNA. Retroviruses that have written themselves into DNA compose 8% of human the genome, These retroviruses in our DNA are known as HERVs, which stands for human endogenous retroviruses. Lastly, the chapter reminds us again that viruses played a key role in the evolution of mankind.

Not Really