wow. this year is
very different from last year.
so much is new for this group of eight alumni and one first timer: college tours, horrible weather, etc. even the style of blog required has changed. i guess the new aspects of the program have come as a shock for some of us
Even though the courses aren't for credit, they're a lot more challenging.
in the morning, i had two labs. in the first one, we pipetted different amounts of food coloring dissolved in hydrogen dioxide into 1.5 ml tubes. In each tube, there was a total of 10 micro liters. then we adjusted the pipets to this amount, and withdrew that much solution to see how accurate our technique was. in two of the tubes, there was exactly ten microliters. however, in my third tube there was a little bit left over.
then, we repeated this process, except using a total of 1000 micro liters in each tube. this allowed us to work on a minute, and not so minute scale, and see how accurate we could be.
Next, we practiced sterile technique. in order to do this, we first lit a bunsen burner. then, we took a 10 ml pipet, and ran it through the flame, paying special attention to the tip. next, we took a 50 ml vial of food coloring and hydrogen dioxide, and ran the edge of the vial through the flame. finally, we withdrew 5 ml from the tube, making sure that we were sterile.
after this, we did another lab. first, we labeled four petri dishes. all of them contained agar. two of them contained an antibiotic. next, we took e. coli, and using sanitary technique again, we placed some of the e coli in each petri dish. first, we made a line of it in the petri dish. next, we sterilized the brush used for plating, and scooped up a little bit of the e. coli that we had in our first line. then, we made a zig zag line with this e. coli. then, we repeated this process until we had a square, with each side less concentrated than the previous. this will allow the sample to have individual colonies grow, as well as larger patches of the bacteria.
then, we spent about ten minutes cleaning up. almost each tool or tube we used had a different trash can that it had to be disposed in. finally, we got to leave for our lunch break.
when we returned for our afternoon session, the professor lectured about last nights reading. first she talked about the basic structure of dna, which is composed of a phosphate group at the 5', a nucleotide at the 3'. the two strands are then held together by hydrogen bonds. cytosine and guanine have three binds, while adenine and thymine have two.
next she talked about synthesis, which occurs unidirectionally starting at the 5 prime end and going towards the three prime. however, it reads the dna strand from the three to the five. thus, the strand of dna created is not a copy, but a compliment to the template strand. however, because dna is antiparallel, one strand has to copy in small segments which are then spliced together.
then she went on to rna transcription. RNA polymerase synthesizes RNA from dna. promoter sites throughout the dna strand signal the polymerase as to where it should begin replication. these promoter sites are specific sequences of nucleotides such as TATAAA or TTGACA. there are multiple kinds of dna, mRNA, rRNA, tRNA, and many others, which serve unique functions in translation—the creation of proteins. This occurs in the ribosome. every three nucleotides codes for an amino acid, of which there are twenty. these three nucleotide segments are called codon. the ribosome binds to the 5 prime end of the strand where it sees the code for methylene. the ribosome acts as a catalyst for the reactions which occur, leading to a complex polypeptide.
thus, from a single strand of dna, enzymes, proteins and rna are synthesized.
Of course, this process occurs extremely rapidly, millions of times per day in a human, so there are infinite possibilities for mistakes. if a single nucleotide is miscoded, as in the case of sickle cell anemia, death can occur.
