masochist

masochist, on May 12, 2010 - 15:02, said:

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 outcome

aa x aa
= aa, aa, aa, aa
= aa as the only outcome

Aa 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

Heya! I am a Geo SL student (exams in a few days!!!) and my teacher did this exact same graph question for us, this is his answer (he was a Geo IB examinator so he should know   ):

"In Country A the GDP per person has slightly increased between 1975 and 2001, but with many small fluctuations. However the under 5 mortality rate has consistently decreased in the same period, from 120 in 1975 to 30 in 2001. The GDP increased from 2800 to 3000.
In Country C the GDP per person has mostly decreased between 1975 and 2001, from about 8000 in 1975 to 6000 in 2001. However the decline has shown many fluctuations. Meanwhile the under 5 mortality rate has consistently declined in this period, from 155 in 1975 to 40 in 2001, with one year as exception, 1977 when it increased."

So you see he quotes numbers and years quite a lot, so that's what I would do as well.

Also when answering graphs both my Geo teachers (I have had two) have their favourite words:
- substantial(ly)
- significantly
- fluctuations
- exception
- slight (eg slight increase, slight decrease or decline)
- rapid (eg rapid increase)
- peak
- "at its highest" eg infant mortality rate was at its highest in ___(yr), at____(number)

You probably already know this but I was always told to remember that when "describing" graphs, you must talk lots about their shape and increases and decreases and quote years and figures and such, i.e. provide an extensive, detailed description, but you must NEVER EVER "explain" the graphs or their shapes. I.e. it would be inappropriate to start speculating in this question that Country B is more developed than Country A and so on.

Well, hope this helps.  

I never did this particular area of chemistry myself, so my apologies if this is wrong -- but could it be: the larger masses reach a peak of reaction, the CaCO3 becomes the limiting factor and therefore the reaction effectively stops. No heat is being given out, and heat is being lost to the environment, so temperature decreases. With smaller masses the reaction continues (this assumes it's a pretty slow reaction) and the temperature continues to rise as the reaction is still occurring -- whereas with the other one it stopped rising pretty quickly as the reaction stopped pretty quickly?

That may be totally flawed I was never that great at chemistry explanations.

All I would say is that if this happened consistently and several times, chances are it was meant to happen. SO if there IS a proper scientific reason (just you have no idea what it is), the person marking it will look at any edited data you give and be like HRMM well that's certainly not how it goes. There's a danger that by correcting for the unknown, you accidentally make a bigger mistake!

I would suggest you follow your passion because that is what will ultimately drive you to get a high grade. Don't take something that you don't like just because most people do well in it. It will be a bad choice in the end.

I'd say download a question bank if you can find one, otherwise ask your teacher. Try A level questions they're the same, might be easier to find on the net  

Hello!

Good on you for choosing Geography I did my EE on The Butler's Model/ Resort life cycle model, based on numerous towns in my local shire. I basically researched into what stage each are at on the model, and come to an overall conclusion as to which stage my local shire is at.

At first I tried to use one of the sample questions, but tweak it to my local area, however I found it to be too difficult, so I had a look through my textbooks to see what I could apply to my local area.

For data collection, I used mostly secondary sources such as books and websites, but I did create my own indexes and surveys, and I held some interviews with residents as my primary sources.

Good luck! I hope i've helped

You can do geography either on already published stats/information or you can conduct your own field study. I have been told by my teacher that the examiners generally like a field study done in the student's own local area, but you can still get great marks by using other peoples' data/info...
Try looking up geographical models or theories and find a way to test these on something.