"Official" 2014 USABO thread

<p>how are we trolls? </p>

<p>For the mice genetics one, is it lethal if one has a homozygous dominant genotype? I thought it was just regular dominant over recessive at first but then it does not work for the subsequent question. The ratios were kinda like 2:1 instead of 3:1 too.</p>

<p>For the allergy one, I knew IgE was for allergy but I was’t sure about the function of IgG. Was the answer A or the other answer with IgG and IgE?</p>

<p>@CheeseBro - Since tomorrow is technically the last day to send in Open Exams, can you refrain from discussing until then? I personally don’t care after that, but just to be safe. Sorry for being a buzzkill </p>

<p>I just took the test today… It wasn’t terribly difficult - it could have been a lot worse - and there were a lot of really obvious answers. I skipped a bunch of chapters in Campbell though (life got crazy), so I don’t know if I made semis… cutoff approximation for this year, anyone???</p>

<p>@elf4EVA I approximate a 33 cutoff. All my friends and I estimate we got 43+. Also, because the T/F section has an average of 50% just by purely guessing, mathematical analysis suggests that the cutoff has to be at least 3 point above last year, since there were 10 T/F</p>

<p>There were 10 TF questions? I thought there were like 5 (at least, I can only remember about 5)</p>

<p>So we can now officially discuss test questions right?</p>

<p>@Lucky139 - Officially, no. At the least, try and wait until tomorrow (since teachers are still sending in exams today)</p>

<p>For everyone wondering about the cutoff - last year, the highest score on the Open was a 42, and the cutoff was 25. I personally didn’t expect a max over 44 and a cutoff of over 29 this year, but @ScienceChamp will probably throw off the former estimate (since that’ll probably be one of the highest scores in the nation)</p>

<p>It was lethal if it was homozygous -
let me explain
It was lethal then the genotype of both yellow plants should have been Yy
Then the offspring should be YY, Yy, Yy, yy
YY would die because it’s lethal so you’re left with two yellow and one gray. Thus a 66% yellow offspring.
So the second question, when it asks for the offspring ratio when a yellow and gray crosses you get Yy x yy
Thus getting Yy, Yy, yy, yy -> 1/2 yellow 1/2 gray</p>

<p>@CheeseBro As for the IgG one you’re left with two choices and it was the one that says IgG performs opsonization or something like that. </p>

<p>And does anyone know the answer to the macrophages and cytotoxic T cell question involving phagocytosis?</p>

<p>Considering we’ve already started asking questions, oh well. Plus it’s teacher policy to burn the test right after it has been taken.
The answer was macrophages. </p>

<p>yesss. I hope you’re right. My friend said it was cytotoxic T cells but idk. </p>

<p>Cytotoxic T cells secrete molecules that destroy the cell, they don’t perform phagocytosis. </p>

<p>kewl</p>

<p>How bout that ion question with Na K and Ca</p>

<p>Higher Na/Ca concentration outside the cell</p>

<p>omg yes</p>

<p>What were the questions on the first page again?</p>

<p>A question about myelin sheath, a question about flagella, and I don’t remember that third question on that page. </p>