This week I decided to stay in genetics again. I slacked a bit and only completed 3 out of 5 tasks, but I still feel accomplished. Here are my notes from this week!
“I watched a video about the structure of DNA. I’ve never taken chemistry classes so I was kind of completely lost. That’s basically it.
The second video was also about the structure of DNA and the different stuff that makes other stuff. I’m clueless. :(”
As you can see, I didn’t really understand anything, even though I tried really hard. I do believe that I learned a little bit, though.
“I don’t think I learned anything. Again. It was all the same sort of stuff as yesterday and I don’t know what the heck I just spent 20 minutes reading.
I watched an interesting video on the transforming principle that I actually understood! It talked about how in 1928 a scientist with the last name of Griffith performed an experiment. He took mice and injected them with different strands (This means viruses). He had rough strands and smooth strands. When he injected rough strands the mice lived, but smooth strands killed the mice. He tried heating up and killing the smooth strands. He then injected the mice with this and, not surprisingly, they survived! Lastly, he tried mixing the killed smooth strands with the rough strands. Logically, the mice would survive. Right? Wrong. The mice died! In 1944 three scientists (Avery, McCarthy, and MacLeod) decided to find out why this was. They did a whole bunch of stuff to killed smooth strands and somehow figured out that the virus had DNA! When Griffith mixed the dead smooth strand and the rough strand, the smooth one’s DNA must have transformed the live rough strand’s to be deadly to the mice.”
This was very interesting to me. I think it’s so cool how this dead virus can overtake the living virus and transform a rough strand into a smooth one!
In the video, I learned about Hershey and Chase, who proved Macleod, Avery and McCarthy’s theory that DNA is the stuff that holds all the information about organisms. They took some T2 Bacteriophage (This is a virus that kills bacteria I think). That did something… Not positive what. They knew that when the heat-killed smooth strand transformed the rough strand into more of the smooth strand, something was injected. They wanted to know if it was protein or DNA. Chase and Hershey though that protein would hold all of the information of the organism, while Macleod, McCarthy, and Avery thought it was DNA.
Man… I understand this in a broader way and it makes sense, but I don’t know how to write it and explain it! I don’t know what did what, just that something did something resulting in something that makes a lot of sense.
Anyway, something from that virus was mixed with/grown with radioactive 32P (phosphorous) and some with radioactive 35S (sulfur). They knew that if DNA was the answer then they would end (somehow) end up with 32P. If it was protein, they would end up with 35S. In the end, they ended up with/found/discovered 32P. That’s how we know DNA holds all of our genetic information!
The article I read was kind of re-explaining what the video said. I understand a bit more. A bacteriophage is a virus that attacks bacteria. The scientists grew this with the 32P and 35S. Here is some stuff to help understand it better (from the article).
“Hershey and Chase knew that the phages attached to the surface of a host bacterial cell and injected some substance (either DNA or protein) into the host. This substance gave “instructions” that caused the host bacterium to start making lots and lots of phages—in other words, it was the phage’s genetic material. Before the experiment, Hershey thought that the genetic material would prove to be protein
To establish whether the phage injected DNA or protein into host bacteria, Hershey and Chase prepared two different batches of phage. In each batch, the phage was produced in the presence of a specific radioactive element, which was incorporated into the macromolecules (DNA and protein) that made up the phage.
One sample was produced in the presence of 35S, a radioactive isotope of sulfur. Sulfur is found in many proteins and is absent from DNA, so only phage proteins were radioactively labeled by this treatment.
The other sample was produced in the presence of 32 P, a radioactive isotope of phosphorous. Phosphorous is found in DNA and not in proteins, so only phage DNA (and not phage proteins) was radioactively labeled by this treatment.
Each batch of phage was used to infect a different culture of bacteria. After infection had taken place, each culture was whirled in a blender, removing any remaining phage and phage parts from the outside of the bacterial cells. Finally, the cultures were centrifuged, or spun at high speeds, to separate the bacteria from the phage debris.”
This was also very interesting to me, however much confusing it was. I don’t fully understand the order of operations but I have an idea of how it works and I like that. Of course, I would rather fully understand it, but having an idea feels nice.
Something I also really like is how there was a woman scientist that helped make the breakthrough discovery about DNA carrying the genetic information versus protein. Everybody else that Khan has talked about (Gregor Mendel, Thomas Hunt Morgan, MacLeod, Avery, McCarthy, Griffith, Hershey) were men. But Martha Chase helped make the definite discovery of DNA.
OTHER NOTES: (keep in mind I’m telling myself I can’t use any outside source to remember things, so I might say I think a lot. I’m relying on my brain alone!)
I finally memorized what DNA stands for! DeoxyriboseNucleic Acid
RNA (something that has the recipe for different amino acids to put it simply) stands for Ribose Nucleic Acid.
I also memorized the scientists who made big discoveries about genetics. At least, the scientists Sal Khan talked about.
Gregor Mendel was in the (I think) 1880s. He did experiments with pea plants and discovered heredity! He noted the ratios of differently colored pea plants. These ratios are spot on and used today!
Thomas Hunt Morgan started breeding fruit flies in 19-something. I know for sure the latest year was 1911.
Boveri and Sutton I think discovered/did something with chromosomes. I believe they came up with the theory that traits and genes sat on chromosomes.
Griffith came up with the Transformation Theory/Hypothesis/Idea. He wanted to come up with a cure for pneumonia but ended up discovering something different. He injected different viruses into mice and discovered that the dead smooth strand could transform live rough strand into smooth strand!
Avery, MacLeod, and McCarthy wanted to figure out why/how the transformation theory worked. They took the smooth strand and found that the virus has DNA! They believed that DNA was the thing that held genetic information.
Hershey and Chase wanted to know for sure if DNA or proteins held genetic information. Hershey was pretty sure it would be the proteins, but he was wrong! The two did a slightly complicated test with stuff and they proved that DNA actually holds the genetic information for organisms.
That’s all the time I have for today; every finished blogging ten minutes ago! Bye!