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AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

Reply 1620

Linked

6

Original post by Suzanna5678

Someone help

Hmm seems tricky is this a pp question

Reply 1621

chuckynoriss

Original post by Mr boombang

anyknow what is the piont of SD?! and what does it do?

SD tell you how spread out the data is, the variation in the data. So the larger the SD the more variation there is in the data and the more spread out it is. When SD bars overlap then it is likely that the results are due to chance :smile:

Reply 1622

Magenta96

16

Original post by Mr boombang

anyknow what is the piont of SD?! and what does it do?

shows the variation of data about the mean, if the standard deviation overlaps then the data is unreliable and if it doesn't overlap then the data is reliable. That's pretty much all you need to know in regards to standard deviation. :smile:

Reply 1623

Sorro10

5

Original post by Magenta96

are we allowed to say endodermis instead of endodermal cells? and okay so it is the endodermal cells that provide the mineral ions and the pressure is caused by water entering the xylem by osmosis. Thank you!

I don't see anything wrong with saying that, but I personally would stick with Endodermal cells to be specific just incase.

Reply 1624

Magenta96

16

Original post by DrFantastic

Was wondering if anyone could help me out;

I'm revising Mitosis but I'm so confused on cell cycle.

I know Mitosis is split into Interphase, Prophase, Metaphase, Anaphase and Telophase but when does the cell cycle start and end?

It's confusing and when there are questions asking "how long were the cells in Mitosis", how on earth do you go about working them out?

Any help at all is appreciated, please quote :smile:

yeah I've seen a question like that. Do you have the actual question though? because you have use values from the question and table or whatever they give.

Reply 1625

Magenta96

16

Original post by Sorro10

I don't see anything wrong with saying that, but I personally would stick with Endodermal cells to be specific just incase.

ok, thank you very much :smile:

Reply 1626

Sapphire123

Original post by Potential Medic

This was also the ISA experiment and we had to calculate the standard deviation afterwards and plot it on a bar chart. But I'm pretty sure we don't have to calculate the standard deviation for this exam?!

Yh it was an Isa we did too that's why I knew about it so when I did the paper I knew a bit more about the experiment but yh we definitely don't need to work out standard deviation just be able to understand the data which may give SD

Reply 1627

Magenta96

16

Original post by DrFantastic

It's the June 2012 paper and it's really getting at me :frown:

right, look at the table, it says 90% of the cells are in interphase. It takes 20 hours to complete a cell cycle so 90% of the cells are in interphase in those 20 hours. 90% of 20 hours is 18 hours. 18 hours are spent in interphase, so 2 hours must be spent in mitosis like the markscheme says. :smile:

(edited 10 years ago)

Reply 1628

WheezyT

2

I'm really confused can someone explain the stages of Meiosis in the form of interphase etc etc cheers!

Reply 1629

Sorro10

5

Original post by WheezyT

I'm really confused can someone explain the stages of Meiosis in the form of interphase etc etc cheers!

This video will help ALOT.

http://www.youtube.com/watch?v=ijLc52LmFQg

Reply 1630

Magenta96

16

Original post by WheezyT

I'm really confused can someone explain the stages of Meiosis in the form of interphase etc etc cheers!

meiosis is similar to mitosis with a few differences. Interphase is not part of meiosis by the way, it's before meiosis. In prophase the chromosomes will shorten, and won't be visible yet.

In metaphase, the chromosomes line up at the equator of the cell and attach to the spindle fibres. Crossing over also occurs, so the chromatids of each of the chromosomes twist around each other causing bits to break off and re-attach to another chromatid, this causes alleles to be exchanged. The independent assortment of chromosomes can also occur so the homologous chromosomes line up alongside each other and switch positions, so each daughter cell gets a different combination of chromosomes.

In anaphase, the chromosomes (not chromatids - that's mitosis) are pulled to opposite poles (centrioles) of the cell, a nuclear envelope forms around each group of chromosomes in telophase and cytokinesis occurs (cytoplasm divides).

Reply 1631

Magenta96

16

Original post by DrFantastic

But isn't Interphase part of mitosis? Forgive me if that's a stupid comment but I didn't follow that :/

no problem, no interphase has nothing to do with mitosis, it's BEFORE mitosis, easy mistake to make though. Basically, the question tells you each cell cycle lasts 20 hours. In the table it told you 90% of the time in a cell cycle is spend in interphase right? So 90% of 20 hours is 18 hours. This tells you the last 2 hours are spend in mitosis. Feel free to quote if anything doesn't make sense though. :smile:

Reply 1632

WheezyT

2

Original post by Sorro10

This video will help ALOT.

http://www.youtube.com/watch?v=ijLc52LmFQg

Original post by DrFantastic

Hey,

Meiosis is nothing to do with Interphase etc.
Meiosis is about making genetically different gametes (sperm and egg cells)

Mitosis is about making 2 genetically same cells :smile:

Original post by Magenta96

meiosis is similar to mitosis with a few differences. Interphase is not part of meiosis by the way, it's before meiosis. In prophase the chromosomes will shorten, and won't be visible yet.

In metaphase, the chromosomes line up at the equator of the cell and attach to the spindle fibres. Crossing over also occurs, so the chromatids of each of the chromosomes twist around each other causing bits to break off and re-attach to another chromatid, this causes alleles to be exchanged. The independent assortment of chromosomes can also occur so the homologous chromosomes line up alongside each other and switch positions, so each daughter cell gets a different combination of chromosomes.

In anaphase, the chromosomes (not chromatids - that's mitosis) are pulled to opposite poles (centrioles) of the cell, a nuclear envelope forms around each group of chromosomes in telophase and cytokinesis occurs (cytoplasm divides).

WOAH! EPIC thanks very much guys :ahee:

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Reply 1633

Magenta96

16

Original post by DrFantastic

So Interphase is NOT part of Mitosis?

Mitosis is then Prophase to Telophase?

yeah interphase has nothing to with mitosis. Then it's just mitosis (prophase, metaphase, anaphase, telophase)

Reply 1634

Magenta96

16

Original post by zbert

what happens during first growth G1, in interphase (cell cycle)

cells grow and proteins are synthesised

Reply 1635

Magenta96

16

Original post by DrFantastic

Oh right, I got it now. Thanks man, appreciate it! :smile:

you're welcome :smile:

Reply 1636

elliewoodheadx

Please could somebody explain immunological comparisons to me again, I've read a couple of other descriptions but i don't know why i just cant understand it..
Thanks in advance!

Reply 1637

MehvishM

Original post by elliewoodheadx

I'm in year 13 and i'm not re-sitting all units but just unit 2 on monday then my unit 5 exam on the 17th! I wouldn't worry, even if it does come to that and you have to do re-sits next June it would actually be really helpful for the unit 5 exam as there is a 25 mark essay at the end which could be on anything from AS and A2! so re-sitting may actually be not that bad since you will have to revise it all any ways, maybe even quite motivating to do more bio work!

arr okay thanks :biggrin:

Reply 1638

Tee Logan x

1

Can anyone explain to me the experiment on p220 of the nelson thornes book. Its about ttransfer of DNA between two strains of e.coli. Thank youu :smile:

Reply 1639