A level Biology: Post your doubts here!

[Autumn98]

anyone who did the bio paper 2 (22) 2015?
Do you remember what answers you wrote for the fill in the blanks on ecology lesson..

 

[My Name]

The answer is C how? I don't get the stage of mitosis part :3

 

[My Name]

The answer is D

 

[My Name]

The answer is A

 

[Lola_sweet]

View attachment 54804
The answer is C how? I don't get the stage of mitosis part :3

Sis remember anaphase is the stage when the sister chromatids are being pulled apart by their keneticores connected to the spindle fibre
so it cant be Anaphase

 

[My Name]

Sis remember anaphase is the stage when the sister chromatids are being pulled apart by their keneticores connected to the spindle fibre
so it cant be Anaphase

Yeah okay fine BUT in METAPHASE they arrange themselves at the equator..
They are more or less scattered in the figure..

 

[Lola_sweet]

Yeah okay fine BUT in METAPHASE they arrange themselves at the equator..
They are more or less scattered in the figure..

by now prophase is over and Prophase is a stage of mitosis in which the chromatin condenses into a highly ordered structure called a chromosome
thus its now getting ready to align at the equator of the cell
if it was anaphase it would look like this:
http://upload.wikimedia.org/wikipedia/commons/3/35/Anaphase.svg

 

[My Name]

The answer is D

 

[My Name]

by now prophase is over and Prophase is a stage of mitosis in which the chromatin condenses into a highly ordered structure called a chromosome
thus its now getting ready to align at the equator of the cell
if it was anaphase it would look like this:
http://upload.wikimedia.org/wikipedia/commons/3/35/Anaphase.svg

I get it that it can't be Anaphase but I though it can't be METAphase either because they'd be at the equator if they were...
Then I guess that its a little like Metaphase so metaphase

 

[Lola_sweet]

I get it that it can't be Anaphase but I though it can't be METAphase either because they'd be at the equator if they were...
Then I guess that its a little like Meta phase so metaphase

Yes tip is always cross off the ones it definitely cannot be
so here it cant be anaphase so A and B is definitely wrong
then u know the number of chromoses in the haploid cell cant be 10 because thats the number in the diploid cell
so D is definitely wrong
that leaves u with c

 

[My Name]

Yes tip is always cross off the ones it definitely cannot be
so here it cant be anaphase so A and B is definitely wrong
then u know the number of chromoses in the haploid cell cant be 10 because thats the number in the diploid cell
so D is definitely wrong
that leaves u with c

Yes thank you ^_^

 

[Lola_sweet]

Yes thank you ^_^

dont mention it

 

[Zhi Qim]

Hi, can i ask for 9700_w02 paper 1 marking scheme?

 

[My Name]

Hi, can i ask for 9700_w02 paper 1 marking scheme?

If and when you find the MS tell me also. Plz and thnx

 

[Liv2Stdy]

Hi, can i ask for 9700_w02 paper 1 marking scheme?

Check the ER , It includes the marking schemes.

 

[My Name]

Check the ER , It includes the marking schemes.

Thank you! I forgot about that.

 

[Liv2Stdy]

Thank you! I forgot about that.

Hehe..Don't we all?

 

[qwertypoiu]

View attachment 54804
The answer is C how? I don't get the stage of mitosis part :3

The cell has been squashed.
The line of chromosomes across the equator were forced into moving and becoming circular like that.
The principle being tested is the knowledge that chromatids have not separated yet in Metaphase, whereas they have in the Anaphase.

 

[My Name]

The cell has been squashed.
The line of chromosomes across the equator were forced into moving and becoming circular like that.
The principle being tested is the knowledge that chromatids have not separated yet in Metaphase, whereas they have in the Anaphase.

I dont get it. :/
What happens if they are squashed?
<I know that the number would be 5 so it can be either A or C >

 

[qwertypoiu]

View attachment 54806
The answer is D

The egg is a haploid cell. After fertilisation, it fuses with another haploid cell to form a single diploid cell. The quantity of DNA has doubled.
The next doubling of DNA content occurs during the S phase of the cell cycle. The DNA undergoes semi-conservative replication. It may not be noticeable under a microscope until Prophase, when we see each chromosome consisting of two chromatids, but we know the chromatin form duplicates before during the S phase.
The reduction of DNA content next, which is what the question is asking about, happens at mitosis, when two new cells are formed from the diploid zygote, so the DNA material is shared. Each get one chromatid from the one chromosome.
This process of increase and decrease in DNA material will continue, each corresponding to S phase and mitosis.
All 4 options given in the question are a part of mitosis.
The point at which we consider the single cell to have truly split into two is when mitosis is complete.
This is at Telophase, after which cytokenesis will complete the separation.