BIOLOGY
Feb. 11, 2019 -
LABS
This section details all of the labs that we have done so far in Lucas's class. The theme of the system has been forensic science, so most of these labs are focused on analyzing parts of the human body.
Forensic Lab One: Hair Analysis
For this lab, we, working in groups of two, collected our hairs and affixed them to a slide. One hair we collected from our clothes, and the other one we pulled out of our scalp in order to examine the follicle. After letting the nail polish that kept our hairs on the slide dry, we put them under the class microscopes. We were examining for different parts of the hair- the follicle, shaft, cuticle, cortex, and medulla.
The follicle is the bulb at the bottom of a strand of hair. It contains DNA of an individual, and can be analysed in order to determine who committed a crime. Because the follicle can be matched to one specific person, it counts as individual evidence. The shaft is the remainder of the hair. It can't be analysed for DNA, but from it's length, color and texture, we can match a hair to a specific group of individuals. Because the shaft can be matched to a class of individuals, it's known as class evidence.
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The cuticle is the rough outer layer of the hair that forms interlocking scales in order to protect the hair. The cortex is the central part of the hair, and comprises most of the strand. The medulla is a line of pigment inside the hair that varies in pattern for each individual.
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The purpose of this lab was to examine the parts of the hair discussed in an earlier lecture by Lucas, and to get comfortable with the microscopes for later labs.
Forensic Lab Two: Who Stole Ross' Expo Marker?
For this lab, we analysed DNA markers using gel electrophoresis to determine who stole Ross's expo marker. To introduce the concept of gathering DNA evidence, Lucas wrote a short story where Ross had one of his beautiful, black expo markers taken and replaced by a terrible yellow marker. To figure out who had taken his marker, Ross took DNA samples from two suspects (Jorge and Fran), and then passed it off to us to match the DNA on the marker to a suspect.
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Before this lab, we had a lecture about DNA profiling from Lucas. From the lecture, we learned that the part of DNA that's analysed to match to a particular person is old, repeating viral DNA that does not code for any traits. Each human has a different number of these repeats (called STRs, or Short Tandem Repeats), and because there's 13 different areas where these repeats are collected from, it's very unlikely that two people share an identical number of repeats across all 13 areas.
When DNA is put into gel electrophoresis, it moves from the negatively charged end of a battery to the positively charged end, because DNA carries a negative charge. Areas with fewer repeats move faster towards the positively charged end, and areas that have a lot of repeats move more slowly. Because each marker moves at different speeds depending on how many repeats there are, and because the number of repeats in each person's DNA is unique, each person's DNA will appear at different locations in the electrophoresis gel. This is useful in criminal cases, because DNA left at the crime scene can be traced back to an individual.
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To the right: an example of gel electrophoresis.
HONORS
This section details the process of my honors project for Biology. For honors, we have to spend a minimum of 12 hours on a project that goes in depth into one biology concept. I chose to make a comic.
My Project
I chose to make a comic about the blue-ringed octopus. This 10 cm long octopus is one of the most deadly creatures in the world, due to it's powerful toxin, which could kill a person in as little as 20 minutes. I wanted to research how it used this toxin, as well as why the toxin was so harmful to humans.
