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OCR AS Biology (F211) - Jan 2013.

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Does anyone have the June 2012 past paper for this exam?
Reply 361
Original post by JamesNeedHelp2
Homologous pairs of chromosomes are approximately the same length and thier centromere is at the same position. One is from the father and the other is from the mother. While their genes are in the same order, they have different alleles that code for different things. For example one of the chromosomes might code for brown hair, while the other might code for blond hair.


Thank you soooo much ! :biggrin:
Reply 362
Original post by the A* guy
A homologous pair of chromosomes is a pair of chromosomes that contain the same genes, but different alleles of the same genes. One of the chromosomes is maternal and the other is paternal. During Meiosis only one of the chromosomes from each homologous pair goes into a daughter cell, creating 4 daughter cells, which are haploid.

I would not worry about homologous pairs of chromosomes, as they came up in june 2012, so its very unlikely for it to come up in jan 2013. :biggrin::biggrin:



And thank you too! Yes it quite unlikely :biggrin: Good luck for next week !
Original post by milworthy
Does anyone have the June 2012 past paper for this exam?


Question Paper is here: http://www.thestudentroom.co.uk/showthread.php?t=2130670&page=14&p=40635842
Reply 364
PANICKING :eek::confused: help?!

I've revised upto section 1.2.2 Transport in animals. I Have half of this left and the whole of 1.2.3 Transport in plants. Ive hardly done any past papers. Advice? what should i be doing right now
(edited 11 years ago)
Original post by theworld
PANICKING :eek::confused: help?!

I've revised upto section 1.2.2 Transport in animals. I Have half of this left and the whole of 1.2.3 Transport in plants. Ive hardly done any past papers. Advice? what should i be doing right now


Finish your revision?

You still have 8 days left, you've got enough time to get a decent understanding of the specification. If you work hard tomorrow, you could finish Transport in animals and plants and then you could tackle some past papers, and see what mark you are getting.
Reply 366
I really need some advice. I constantly reread notes and material but as soon as I get into exams I go blank. What are some of your techniques on exam days? I was thinking about waking up reeeeally early like 5am on the day and going through everything before hand, bad idea?


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Reply 367
Original post by Lola M
I really need some advice. I constantly reread notes and material but as soon as I get into exams I go blank. What are some of your techniques on exam days? I was thinking about waking up reeeeally early like 5am on the day and going through everything before hand, bad idea?


Posted from TSR Mobile


I think the latter is a really really bad idea, the best thing is to be relaxed, which means get a good night sleep. Eat a good breakfast at the table don't rush. And overall be confident in the exam, this can only happen by revising and taking in the content. If you do that you should be fine. Also practice past papers a lot. Not just once, I've done every past paper at least once. You will soon see the progress.
Reply 368
Hi-actually what topics came up on OCR AS unit 2 in the summer that guys are taking on January 15th? My school has had no mocks, so don't have the questions to look at again. Thanks.
Reply 369
H jn B b co.


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Reply 370
good luck to everyone in your exam
(edited 11 years ago)
Pretty simple question I think. But can anyone tell me what are sieve tube elements for? Thanks


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Original post by SwitchingOne
Pretty simple question I think. But can anyone tell me what are sieve tube elements for? Thanks


This was posted from The Student Room's iPhone/iPad App


Phloem tissue transports solute (translocation). The tissue is comprised of two types of cells, sieve tube elements and companion cells. The sieve tube elements have no Nucleus or Ribosomes and very few mitochondria, forming a tube to allow the movement of solutes to take place. However, translocation is an active process which requires energy so the companion cells provides energy and nutrients which diffuse into the sieve tube elements through the Plasmodesmata.

Diagram

(edited 11 years ago)
Reply 373
Need help with magnification, don't get the calculations involved ?
Original post by imthe12
Need help with magnification, don't get the calculations involved ?


The formulas is:

M = I/A
I = M x A
A = I/M
Normally you just have to use these to work out what it's asking you.


What exactly do you not understand?, then i can help.
Is there a particular question that you can't do?

:smile:
Reply 375
Original post by the A* guy
The formulas is:

M = I/A
I = M x A
A = I/M
Normally you just have to use these to work out what it's asking you.


What exactly do you not understand?, then i can help.
Is there a particular question that you can't do?

:smile:


I don't get this question and the units In regards with converting
Original post by imthe12
I don't get this question and the units In regards with converting


You would use the equation Actual Size = Image Size / Magnification

The magnification in the question is given as x25000. The image size is 3mm, which is 3 x 106 nm (3000000 nm). Put this into the equation:
Actual Size = (3 x 106)/25000;
Which gives you 120nm
Original post by imthe12
I don't get this question and the units In regards with converting


You're told that the IMAGE SIZE is 3mm wide, but the question is asking ACTUAL SIZE in nano metres

So, firstly, you convert you image size to nano metres, (from mm - nm is multiplying my 1,000,000)
3 x 1000000 = 3,000,000

Next, you are told the the magnification is 25000x

so we use the formula: A = I/M

I/M = 3,000,000/25,000 = 120nm

ANSWER TO QUESTION: 120nm

HOPE THIS HELPS :biggrin::biggrin:
Reply 378
Original post by the A* guy
You're told that the IMAGE SIZE is 3mm wide, but the question is asking ACTUAL SIZE in nano metres

So, firstly, you convert you image size to nano metres, (from mm - nm is multiplying my 1,000,000)
3 x 1000000 = 3,000,000

Next, you are told the the magnification is 25000x

so we use the formula: A = I/M

I/M = 3,000,000/25,000 = 120nm

ANSWER TO QUESTION: 120nm

HOPE THIS HELPS :biggrin::biggrin:



Thanks for your clear explanation, could you list all the conversion units , mm, mm etc.e.g u said x1000,000 for Nm.
(edited 11 years ago)
Reply 379
Or for the above use the triangle:

....I....
..A M....

Cover up one to find the other, just remember I AM in the exam, easy to remember :smile:

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