The Hershey and Chase experiment is vital in the study of genetics. This ecperiment prooved that DNA is the hereditary material in bacteria and bacteriophages. This experiment radioactively labeled the phosphorous in DNA, and the sulfer in protein in a bacteriophage. The bacteriophage was allowed to infect a bacterial cultrue. Hershey and Chase used a blender to separate the bacteriophage from the bacteria, after the infection. They then placed the cells in a centrofuge and let the materials separate by weight. The heavier bacteria fell to the bottom of the centrofuge to form a pellet, while the lighter bacteriophage was suspended in the supernate. The radioactively labeled phosphorous in the DNA was found in the pellet, the radioactively labeled sulfer was found in the supernate. This proved that the DNA was the hereditary material of the bacteriophage, and baceria, and not the protein which remained outside of the bacteria.
I recently looked at an orange juice bottle and noticed a small label that said, 'From concentrate with vitamin C', which made me wonder how is this different than juice straight from a fruit. Upon researching the topic I realized there wasn't much of a difference and the reason why juices are from concentrate or not is due to transport. Both processes begin with raw fruit sent through a juicing machine to remove the skins or peels. Now there are two options. First, the juice could be immediately pasteurized, a process where the juice is heated to kill any pathogens, and eventually packaged and shipped. This process is very simple, however, the juice may not be able to last very long in transit. This is where option 2 becomes beneficial. The juice can be extracted, then run through a second extractor to remove the water content. With no water present in the concentrate, the volume is much smaller and can now be transported to a second location, ideally closer to an intended market. In that second location, the concentrate has water re-added. Now it can be pasteurized and packaged for sale. Unless the seller intentionally adds more to the juice such as added sugar or vitamin C the juices are identical and neither is necessarily better or worse for you.
Mendel, one of the founding fathers of genetics, was well known for his empirical approach to genetics. Through his studies of pea plants, he was able to discover that specific morphological characteristics had variable traits from plant to plant. These traits were able to be passed down from the parents into the next generation of pea plants. Among these traits, some of them are dominant while other are recessive. Through self fertilizing the pea plants, Mendel was able to identify true breeding plants. These plants are known as homozygous now. When two true breading plants were crossed, they produced plants which contained both variables of the trait.
In my microbiology class, we are learning in depth about replication, transcription and translation. Each time a cell replicates, the double strands of DNA splits in 2. Each of these single strands are soon going to become a double strand as they were getting their DNA copied. In transcription, DNA is transcribed to mRNA. This carries the necessary information for protein synthesis. mRNA trasncription occurs in the cytoplasm. Addditionally, transcription is the first step in gene expression. Then, tRNA occurs in the nucleus, and rRNA occurs in the nucleoulous. The translation machinery occurs in the ribosomes, which acts like a taxi in the eukaryotic cell. At the end of translation, we have a polypeptide.
For breast feeding mammals, only the infants and the young are able to breakdown lactose. Once they reach an age of maturity, the gene which produces lactase, the enzyme which breaks down lactose, is turned off. Since lactose cannot be broken down into simpler sugars, it reeks havoc on the small intestine. Perhaps, this the gene turning off was to keep the breast milk only going to the infants of the population and not to the older individuals which have more food choices available to them. Although not everyone can break down lactose, there are certain human populations which have this ability. These populations are those who domesticated animals and use their milk as a key part of their diet. Through the four forces of evolution, the ability to digest lactose in adulthood has persisted around the world. It only takes a single point mutation to turn on the gene which produces lactase. There is no way of telling if this mutation occurred once in history but it likely that convergent evolution was at play. Next, gene flow or the interbreeding of humans continued to spread the gene. Natural selection also increase the prevalence of this gene in population that domesticated animals. Finally, the founder’s effect, a type of genetic drift, would have spread this ability to new colonizations with a high probability of the members having the mutation.
How technology has changed medicine and its history?
I am interested in finding out how far medicine has moved in solving a variety of problems related to human health, with and without technology. I would like to compare the challenges that are faced by modern medicine and that of a century ago. For example, cancer is still not conquered, previously unknown viruses appear with enviable regularity, antibiotics lose their strength, new habits and lifestyle bring new diseases. At the same time, we are at the epicenter of the genetic revolution, intensively studying the structure of the brain, relying on big data and robots, waiting for breakthroughs in the fight against aging.
I am also interested in understanding how healthcare will be affected by an increase in the sophistication of technology. Personally, I predict that with technology we will see a rise in personalized therapy. This is because personal online doctors exist today, but over the coming decades they might dominate the professional environment. Not a single person interested in a healthy lifestyle will refuse instant access to expert opinion, especially if there is a convenient platform for this, and diagnostic tools are at hand. The work of the doctor will be similar to the work of a personal trainer and psychoanalyst. This idea is similar to what I have read in our book SHA about the physicians of the 19th century.
I did not really understand what Abraham Flexner meant by “Medical students must be trained to regard the body as an infinitely complex machine”?
Are Flexner’s suggestions for improving the medical education system still acknowledged today? I am asking this because we currently have more than 31 medical schools in the nation. How does this affect medical education today?
How did the rise in medicine in the US affects medicine today? For example, the rise of cost in medical education, shortage of medical doctors, and the cost of medical care.
How did the low “wage” for physicians like Brisbane affect mediccal practice? Was this the main contributor for the shift in public and private family dynamics?
Abraham Flexner is a prominent figure in the history of modern medicine within the United States. He played a key role in introducing modern methods of teaching medicine in the United States. A report he published in 1908 criticized the quality of teaching medicine and the prestige of the 155 medical colleges at that time. He proposed two ways to revolutionize modern medicine. One way was to reduce the number of medical schools to 31. The other way was to ensure that medical schools are committed to medical research and academic excellence. Abraham Flexner’s ideas also had a heavy affect on American homeopathy. Among the main recommendations given in the Flexner report, there was a requirement that the curriculum of medical schools be based on generally accepted classical practice, which, in fact, put an end to the education of homeopathy in major hospitals.
Over the past 40 years, the bird population in the United States and Canada has declined by 29% or almost 3 billion birds. Research was conducted by American scientists at the Cornell Laboratory of Ornithology. According to the results, of the 3 billion dead birds, 90% belong to common families, in particular sparrows, finches and swallows. They play an important role in food chains and support the functioning of ecosystems, such as pest control.
The study noted that bird losses in North America are similar to bird losses in other parts of the world. Co-author of the study, John Sauer, believes that the main factor that affects the extinction of birds is habitat loss, including due to intensive farming and urbanization. Scientists suggest that further climate change will worsen the situation.
Synaptic plasticity is a concept that had always seemed interesting to me. Even after birth, your brain is capable of changing its connections and wiring. It best described by Donald Hebb's words on long-term potentiation: "Neurons that wire together, fire together". The concept of long-term potentiation involves three stages: input, induction and expression. During the input period, the presynaptic neuron fires a single action potential. This causes a small post-synaptic potential. During induction, multiple action potentials are fired repeatedly along the presynaptic neuron, leaving very little time for the postsynaptic neuron to fire a small action potential and then die down. As a result, the postsynaptic potentials keep bulidng up and reach a threshhold where the neuron is depolarized, leading to an action potential to be fired. This event of accumulation of potentials over a brief period of time is called temporal summation. Finally in the last stage, we see that a single action potential, like the one in the first stage, is able to cause a full action potential called the excitatory postsynaptic potential. This is essentially how we learn. If we keep introducing the same stimulus over and over again, the wiring in our brain adjusts to fire a strong action potential. However, our brain does have a capacity for how much we can learn. The neurons can get too saturated with new wirings if there is no way to reverse this process. Thus, certain wirings start getting weaker by time and this is called long term depression. This would be another way of saying that we are slowly forgetting what we had learned.