lobsta Posted May 12, 2010 Report Share Posted May 12, 2010 Yea you guys are right, its just that i am qutie panicked at the moment..My teacher told me that the internal assesment 33/45 isn't too bad and it will shift my grade up since I am aiming for a 3. I looked at the grade boundaries of 2006 and for a 3 I need 35/100, which I hope I can get. Another question I forgot to ask is, is there a grade boundary for each paper? so if I do good in paper 1 and screw up paper 2 and 3, does that work? or do I need to get a 3 in each paper? Thank you. Reply Link to post Share on other sites More sharing options...
Sandwich Posted May 12, 2010 Report Share Posted May 12, 2010 Each paper contributes a certain percentage to the overall course. So if you do well and got 100% in Paper 1, you'll have say 20% out of the total 100% for biology. I can't remember exactly how each paper breaks down, it's in the syllabus, but basically you need to do well in all of the papers. I assume you'd have to do that no matter how the system worked! There's no grade boundary for each paper, but they can only contribute X% each to the final total. If you don't get a '3' worth of marks per paper, you won't get a 3 overall. Or you could do well in 2 papers and badly in a 3rd and maybe get a 3.Your IA marks aren't that bad, but don't rely on them. It's a really bad mindset to be point counting and aiming for the minimum when you could be revising in the same time and aiming for the maximum you can personally achieve at this point in time! My advice is that the Bio syllabus is long. Get started now, learn as much as possible, and see what happens. You'll get a better grade doing that than you would sitting trying to work out how the points may or may not add up Reply Link to post Share on other sites More sharing options...
lobsta Posted May 12, 2010 Report Share Posted May 12, 2010 Good point! , thanks alot for your help, I guess the only way to pass is by studying. It's just that I am so scared about paper 2. I keep looking at the past papers and I mean I can maybe do around 20/40 at paper 1 but paper 2 is just suicide.. I really dont understand anything there... Specially that section A where its all about an experiment and graphs.. I find it quite hard to understand the purpose of the experiment and therfore analyse the graphs and data properly... Oh well... guess i just need to start studying and memorizing although i have other exams tommorow and friday, so that only leaves me saturday and sunday to study for bio :( Reply Link to post Share on other sites More sharing options...
Mahuta ♥ Posted May 12, 2010 Author Report Share Posted May 12, 2010 If you are afraid of section A, then make sure you prepare for B well. Section B is just about knowing and studying the syllabus, it's not that hard. Never ever depend on IAs, they betray you, and they betray you hard. I got down from a 7 to a 6 just because of my IA. Reply Link to post Share on other sites More sharing options...
lobsta Posted May 12, 2010 Report Share Posted May 12, 2010 Ouch , well thanks for your recomendations. I guess I will just study for Section B and do what I can in Section A. By the way,I guess my IA can't betray me too much since I am only aiming for a 3, nothing that high Well at least I hope it doesn't betray me. Thanks alot! Reply Link to post Share on other sites More sharing options...
Mahuta ♥ Posted May 12, 2010 Author Report Share Posted May 12, 2010 No problemo, prepare well for section B first, then IF you had the time, go through section A, you cant really revise for that. Reply Link to post Share on other sites More sharing options...
masochist Posted May 12, 2010 Report Share Posted May 12, 2010 can some one help me out with this q?i don't know how to do it Reply Link to post Share on other sites More sharing options...
lobsta Posted May 12, 2010 Report Share Posted May 12, 2010 can some one help me out with this q?i don't know how to do it I can't remember the exact number of that nuclotide thing but the answer is either C or D, i am guessing its C.. Reply Link to post Share on other sites More sharing options...
masochist Posted May 12, 2010 Report Share Posted May 12, 2010 its C but can you explain to me why?i don't get how you do that questioncan someone help me out with this one too: Reply Link to post Share on other sites More sharing options...
Sandwich Posted May 12, 2010 Report Share Posted May 12, 2010 can some one help me out with this q?i don't know how to do it To explain:Every amino acid has a tRNA molecule.Every tRNA molecule has an anticodon of 3 nucleotides.Every tRNA must slot onto codon of the mRNA, which is also 3 nucleotides long.So in short, every amino acid is coded for by 3 bases/nucleotides (via tRNA). Therefore however many amino acids there are, there should be about 3x as many nucleotides as there are amino acids on the mRNA. Hope that makes sense.And to answer your second question, the answer is A.That's because a test cross is a recessive parent - i.e. aa as their genotype. Half of the offspring express the dominant gene, and half don't. That means the parent you're interested in must have the dominant gene (otherwise none of the offspring would, there's nowhere else for it to come from!). However, if your parent was homozygous and had both AA genes, that wouldn't explain the fact that half of the offspring are recessive. ALL of the offspring would be recessive, because there's no offspring which wouldn't have Aa as their genotype and therefore express the trait in their phenotype. As half of the offspring are recessive and therefore aa and the other half dominant and therefore Aa, you can deduce that the parent must have Aa as their genotype. Therefore they're heterozygous To do it as one of those chart things:AA x aa= Aa, Aa, Aa, Aa= Aa as the only outcomeaa x aa= aa, aa, aa, aa= aa as the only outcomeAa x aa= Aa, aa, Aa, aa= Aa and aa as the outcomes in a 50/50 ratio <--- describes the scenario.The trait can't be polygenic because otherwise there wouldn't be just two outcomes, there'd be a gradient with some partly expressing, some fully expressing, some expressing a little bit less than fully but more than partly... etc. xP 1 Reply Link to post Share on other sites More sharing options...
masochist Posted May 12, 2010 Report Share Posted May 12, 2010 Thank you so much that was extremely helpful! Reply Link to post Share on other sites More sharing options...
masochist Posted May 12, 2010 Report Share Posted May 12, 2010 Argh could someone help me out with this one too?I guess genetics is really my weak point Reply Link to post Share on other sites More sharing options...
Sandwich Posted May 12, 2010 Report Share Posted May 12, 2010 Okay Well to go through them all...A. Can't be right because they just told you crossing over occurs sometimes, and for all of the gametes to be Ab and aB, crossing over would occur almost never.B. Can't be right because although crossing over does occur, it's only occasional. Generally the genes, as they said, are linked, so no way are the odds going to be the same as for unlinked genes. Linked genes are inherited together in a much higher proportion than due to random mixing.C. No because ab would require crossing over, which isn't all that frequent, whereas the Ab gamete is very likely because those genes are stuck together.D. Yes, because Ab is the linked gene and so A and b are very likely to be inherited together. For ab to occur, you'd have to have crossing over and genetic alteration, which doesn't happen very often, so the offspring are far more likely to be Ab than to be ab. Reply Link to post Share on other sites More sharing options...
masochist Posted May 12, 2010 Report Share Posted May 12, 2010 (edited) edit: THANK YOUim really sorry could someone help me out w these two as well? =/ Edited May 12, 2010 by masochist Reply Link to post Share on other sites More sharing options...
lobsta Posted May 12, 2010 Report Share Posted May 12, 2010 My bio sucks but are the answers for both of them B? Reply Link to post Share on other sites More sharing options...
Sandwich Posted May 12, 2010 Report Share Posted May 12, 2010 The answer to the second one is A, because remember DNA replication is only semiconservative, so each of the new helices must contain a strand from the old bit of DNA. By elimination...In A you have 2 different strandsIn B you have 2 of the same strand so obviously one of them must be a new strand because they can't both be that strand from the original helix.In C you have 2 strands being radioactive within the same helix, which isn't possible because at least one strand per helix must be from the original DNA.In D you have 4 radioactive strands, which isn't possible because not all of the strands came from the new radioactive DNA, 2 of them are from the original so won't be radioactive.As for the first question:Two genes each with 2 alleles options: AA, aa, Aa and BB, bb, Bb, so...AABBAAbbAABbaaBBaaBbaabbAaBBAaBbAabbI get 9 possible combinations, so my answer would be 9 different possible genotypes. 1 Reply Link to post Share on other sites More sharing options...
Mahuta ♥ Posted May 12, 2010 Author Report Share Posted May 12, 2010 Not all MCQ are expected to be asnwered immediatly. When in doubt, just go step by step, if you know the concepts and common sense that goes with it, you will figure it out eventually, dont freak out, but don't spend waay too much time on that question.Don't let weird things like radioactive DNA confuse you, they just mean a certain type of DNA, the first thing that should come to your mind is semi conservative replication. Reply Link to post Share on other sites More sharing options...
masochist Posted May 13, 2010 Report Share Posted May 13, 2010 It's only no. b that i don't get how to do: Reply Link to post Share on other sites More sharing options...
Mahuta ♥ Posted May 13, 2010 Author Report Share Posted May 13, 2010 The unit given to you is in macrometers, you measure how many centimeters that 1 macrometer scale bar is. Say its 4 cm.Every 4 cm of that picture is 1 macrometer in reality.13.2/4= 3.3 macrometers is the actual length of the cell.magnification= measured size / actual size. measured size= 13.2*1000= 13200 macrometersmagnification= 13200/ 3.3 = 4000The picture is 4000 times the actual size.Please check if this is correct. Reply Link to post Share on other sites More sharing options...
masochist Posted May 13, 2010 Report Share Posted May 13, 2010 hm i pasted the answer from the QB as well - it said it was 26000 x 15000 Reply Link to post Share on other sites More sharing options...
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