<p>“The maximum sustainable yield is usually higher than the optimum sustainable yield and maximum economic yield” according to Wiki <a href=“Maximum sustainable yield - Wikipedia”>http://en.wikipedia.org/wiki/Maximum_sustainable_yield</a>. Thus would the answer for that optimal population question on open be the point before the one that has maximum slope?</p>
<p>@ChessNBio I just looked at 45 and got 1:1 (A). Mutant alleles A and B cause the white phenotype when paired with themselves (AA and BB) or the wild-type allele W (AW, BW), and the yellow phenotype when paired with the other (AB). An AA and a BB individual are crossed to produce the all-yellow AB F1 generation. Crossing the F1 individuals should result in a 1 AA: 2 AB: 1 BB ratio, which is phenotypically 1 yellow: 1 white.</p>
<p>@radulae the last piece of information is simply telling you that there is no way of telling whether the parents are carriers or not. That just means you answer, 1/8, is unchanged</p>
<p>@botherme I agree that that’s likely what they intended, but the wording is very misleading. There were definitely people (like me) who thought it was a conditional probability problem and skipped.</p>
<p>I don’t understand how it could mean anything else. It doesn’t change the probability of the next child to have a certain disease even if all of the rest before it had it</p>
<p>@botherme It makes sense to me that if a mother has five unaffected children, she’s less likely to be a carrier. Each of the children is independent, though, so you might be right that it won’t change the probability.</p>
<p>For bluerose’s problem set, I got the same answers as botherme for A, B, and C. I got r=3/32 for D, though, which gives me 3/160 for the maximum risk Laura can incur.</p>
<p>How did you get 3/32? Also, I think I see your point about the other problem, but that is overthinking it way too much lol (the answer key says its a too)</p>
<p>The uncle’s grandfather has r=1/8 from Laura and the uncle’s grandmother (effectively Laura’s grandmother as well, because of the twin thing) has r=1/4. The uncle’s mother should have r=(1/8+1/4)/2=3/16, and the uncle should have r=(0+3/16)/2=3/32.</p>
<p>thx… I just completely misread that pedigree</p>
<p>Hello! i was wondering if its strange for me not to have my scores posted on my USABO account yet. this was my first year competing and neither i nor my incapable teacher have any idea wat the norm is…id really appreciate it if someone could answer this question for me .-.</p>
<p>^Scores should be posted next week, according to their calendar.</p>
<p>@blueroses67 - It was fun to do the genetics questions. Do you have more?</p>
<p>thank u ChessNBio! i really appreciate it. holy ■■■■…we only have a week to review for the semifinals…that some bullcrap right there. so much more less time than for AIME lol</p>
<p>Botherme and Radulae have the right answers. (They’re also right about the open question, iirc - you’re told the person has unaffected siblings, but that doesn’t change the odds that they are affected themselves.)</p>
<p>If you thought that genetics question was too easy, look up the song “I’m my Own Grandpa” and draw the pedigree / work out coefficients of relatedness. (I gave up on trying to make it into a Finals question…too hard!)</p>
<p>Also, if you need a resource for flower formulas, I recommend <a href=“Digital Flowers”>http://www.life.illinois.edu/help/digitalflowers/</a> (remember that you only need to know the ones on the current IBO syllabus).</p>
<p>wow, another really helpful resource. Again, thanks!</p>
<p>I don’t know if I should start studying now or wait until i know if I made it into semis… only one week in between but I don’t want to study if I didn’t make it anyways lol.</p>
<p>How do I sign up if my school isn’t registered?</p>
<p>you can’t sign up now, sorry. The open exam has already passed</p>
<p>Can someone explain how to figure out the correct answer for this question from 2011 Semifinal #1</p>
<p>If you extract the genetic material of the Bacteriophage (X174), you will find that its composition is 25% A, 33% T, 24% G, and 18% C. How would you interpret these results?</p>
<p>A. The experiment’s results must be erroneous; something went wrong
B. We could admit that the %A approximately equals that of T, and the same is true for C and G. Consequently, Chargaff’s rules are followed and the DNA is double stranded
C. Because the %A does not equal the %T, nor does the %G equal the %C, the DNA is single-stranded; it is replicated by special enzymes, following a particular replication pattern, with the single-stranded chain as a template
D. Because the %A does not equal the %T, nor does the %G equal the %C, the DNA must be single-stranded; It replicates by synthesizing a complementary strand and uses the double stranded form as a template
E. Bacteriophage (X174) is an RNA virus</p>
<p>A. This choice is never right, lol
B. Any self-respecting scientist will not mess up that bad
C. If the single-stranded DNA is directly replicated, it’s going to produce a template strand that is the opposite of its actual gene compositions.
E. RNA viruses have uracil
D. This option is the only one that makes sense and results in the creation of strands of DNA that are the same as its original composition. Or just study up and know that single-stranded DNA viruses do this :p</p>