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AQA BIOL2 ~ 21 May 2012 ~ AS Biology

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Original post by izzwizz
Hey, does anyone know topic to revise for the AS ISA with the practical of dipping paper in enzymes and placing it in hydrogen peroxide maybe? It's the second ISA, thank you :smile:


It was my 1st Biology ISA. Revise enzymes and osmosis. That is all you're allowed to be told.
Reply 61
Avatar for SinghH
SinghH
My book says gametes have 23chromatids - if there are 23 chromatids in a gamete, how do we get a diploid when fertilization happens because 23 chromatids and 23 chromatids form 23 chromosomes when there should be 23 pairs of chromosomes in a diploid cell meaning 46 chromosomes so this doesnt make sense help

Image0606.jpg
Reply 62
Avatar for Kay79
Kay79
Well I can see were you're coming from, and during the process of thinking how I was going to try and explain it, I may have actually gone and confused myself :')

I'll give it a go anyway.

The reason is that in Meiosis 1, the 23 homologous pairs of Chromosomes get slit creating 2 new daughter cells and the during Meiosis 2 , the 23 chromosomes in both daughter cells split into 23 chromotids in the (haploid cell) as you said.

I think were you might be getting confused is in the way your thinking that a chromosome as two chromatids however that isn't always the case as A chromosome can be one of two things:

A. A chromosome with TWO chromatids connected at the centromere (a "duplicated chromosome")

B. A chromosome with ONE chromatid connected by a centromere. (an undiplicated chromosome)

However I think the essential piece of information that's actually missing here is that like Mitosis, before Meiosis actually begins there is a process of inter-phase where the chromosomes are replicated.

This animation might be helpful :smile:

[video]http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter3/animation__how_meiosis_works.htm l[/video]

Hope that helped a little.
Reply 63
Avatar for Sorro10
Sorro10
OP
5
Original post by Kay79
Well I can see were you're coming from, and during the process of thinking how I was going to try and explain it, I may have actually gone and confused myself :')

I'll give it a go anyway.

The reason is that in Meiosis 1, the 23 homologous pairs of Chromosomes get slit creating 2 new daughter cells and the during Meiosis 2 , the 23 chromosomes in both daughter cells split into 23 chromotids in the (haploid cell) as you said.

I think were you might be getting confused is in the way your thinking that a chromosome as two chromatids however that isn't always the case as A chromosome can be one of two things:

A. A chromosome with TWO chromatids connected at the centromere (a "duplicated chromosome")

B. A chromosome with ONE chromatid connected by a centromere. (an undiplicated chromosome)

However I think the essential piece of information that's actually missing here is that like Mitosis, before Meiosis actually begins there is a process of inter-phase where the chromosomes are replicated.

This animation might be helpful :smile:

[video]http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter3/animation__how_meiosis_works.htm l[/video]

Hope that helped a little.


Thanks!
Reply 64
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Sorro10
OP
5
Original post by Sorro10
Thanks!


:[]
Reply 65
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Sorro10
OP
5
ISA soon ;s
Reply 66
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jamessssx
I'm bare scared how do i revise for this exam? and how do i revise for the ISA i have like 3 coming up :frown: xx
anyone done the EMPA yet?
Original post by Sorro10
ISA soon ;s


You haven't done your ISA yet? :O
Has anyone done the test paper for the daffodil isa yet ?
Had first ISA last week (one with catalase and different concentrations) and got the second one tomorrow on osmosis/plant stalks... sigh.
Reply 71
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Sorro10
OP
5
Original post by Mocking_bird
Had first ISA last week (one with catalase and different concentrations) and got the second one tomorrow on osmosis/plant stalks... sigh.


Our ISA doesnt start until after Easter for some reason is everyone having theirs now?
Reply 72
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Sorro10
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5
:redface:
Original post by Sorro10
Our ISA doesnt start until after Easter for some reason is everyone having theirs now?


I've got my practical tomorrow, and then the written paper on Monday. We've got 2 classes, and the other class is doing their practical this Thursday and the written paper on the Friday.

I think we're doing it before Easter so we can just come back and get straight into revision mode in lessons without any interruptions/distractions.
Original post by Sorro10
Our ISA doesnt start until after Easter for some reason is everyone having theirs now?

We're doing ours now for the same reason as Tullia.
I feel so behind though, we've only got through 2 booklets with 3 more to go still, eek :frown:

Original post by Tullia
I've got my practical tomorrow, and then the written paper on Monday. We've got 2 classes, and the other class is doing their practical this Thursday and the written paper on the Friday.

I think we're doing it before Easter so we can just come back and get straight into revision mode in lessons without any interruptions/distractions.


Have you got the sucrose/plant stem one tomorrow? I just did that one today if it is :smile:
Original post by Mocking_bird
Have you got the sucrose/plant stem one tomorrow? I just did that one today if it is :smile:


Yes, that's the one. I've been informed it is a fairly straightforward practical, so it shouldn't be too bad. I've got lots of resources for the written paper as well, so if I get my head into that over the coming days then that should be OK as well.

How did you find it? Obviously you can't go into specific details, but I've heard that it is a fairly crude experiment (and so their is a large variation in data between students)?

:smile:
Original post by Tullia
Yes, that's the one. I've been informed it is a fairly straightforward practical, so it shouldn't be too bad. I've got lots of resources for the written paper as well, so if I get my head into that over the coming days then that should be OK as well.

How did you find it? Obviously you can't go into specific details, but I've heard that it is a fairly crude experiment (and so their is a large variation in data between students)?

:smile:


Yeah the experiment was straight forward, although I had a bit of a derp/panic moment at the beginning with step 1 (You'll see it tomorrow and laugh at me because I was panicing for no reason as it turns out you get another sheet to help you with it).

Much more enjoyable than the catalase/peroxide one, but maybe thats just because I enjoy using scalpels :laugh:.

I know you dont need to be told this Mr. 100 UMS (:tongue:) but be really careful when you're doing the heading for your dependent variable, as loads of people messed up on it in my class.

Edit: Oh and I think there will be a large variation because some people will... Hmm how to word this without giving anything away... during the final stage theres something they accidentely do which will mean it will manipulate the shape.
(edited 12 years ago)
Reply 77
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stoppy123
4
After getting 1 mark off an A in my BIOL1 I want to get a mid-high A in this to bring that up :smile:

I've found this unit ok, not too bad, however I may discover I hadn't learnt anything when I do my past papers :facepalm:

The ISA I did though, retaking that... haha
Reply 78
Avatar for EffKayy
EffKayy
16
How is everyone getting on with this unit????
Original post by EffKayy
How is everyone getting on with this unit????


Meh... major meh :tongue:
I did well on the 2 end of unit tests we've done, got another coming up on Thursday on Variation and tings; just finding it a little dull in what we've done so far.

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