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A level Biology: Post your doubts here!

joanna omar

joanna omar

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princeali97 said:
sorry to say but its a completely wrong answer.:oops:.You have answered the consequences of uncontrolled mitotic division.
U have to explain why the cells after mitosis are identical.Its because of semi-conservative replication.And then u describe it.And i was asking for that description.Heres the question.q1 (b)(ii)...


http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w07_qp_2.pdf
Click to expand...

HOOWW but isn't the same Q as in this year
Q1 (C) ???
http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_s05_qp_2.pdf
 
Karim Nabil

Karim Nabil

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princeali97 said:
sorry to say but its a completely wrong answer.:oops:.You have answered the consequences of uncontrolled mitotic division.
U have to explain why the cells after mitosis are identical.Its because of semi-conservative replication.And then u describe it.And i was asking for that description.Heres the question.q1 (b)(ii)...http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w07_qp_2.pdf
Click to expand...
dude... please be more specifico_O
i answered based on your question above, it was asking why cells are genetically identical but in the qp, it is saying how mitosis produce genetically identical cells.
answer will be:
  1. DNA replication is semi-conservative
  2. idea of complementary base pairing
  3. each daughter cell receive exact copy of DNA with same no. and type of parent's chromosomes
 
princeali97

princeali97

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Karim Nabil said:
dude... please be more specifico_O
i answered based on your question above, it was asking why cells are genetically identical but in the qp, it is saying how mitosis produce genetically identical cells.
answer will be:
  1. DNA replication is semi-conservative
  2. idea of complementary base pairing
  3. each daughter cell receive exact copy of DNA with same no. and type of parent's chromosomes
Click to expand...
Excuse me:cautious: ! i was specific.Infact i had posted exactly the same question that was given in the paper.U were'nt able to realise it.If i had posted the link to the question then u wud have answered easily by referring to the M.s :p..anyways i wasnt impressed by yor answer too.U copied exactly from the m.s.Thank you for the mark scheme (y)(y):sneaky:
 
princeali97

princeali97

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joanna omar said:
HOOWW but isn't the same Q as in this year
Q1 (C) ???
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s05_qp_2.pdf
Click to expand...
No,both are completely different questions:whistle:.One is asking "why genetically identical cells are produced after mitosis" and the other is asking "why exact copy of DNA is produced during replication"In the first one u describe about semi-conservative replication in which each strand of DNA acts as a template and complementary base-pairing occurs producing two double helices that are genetically identical.In the second one u describe about mutation because u know that any change in DNA structure leads to mutation so an exact copy of DNA has to be produced.
 
Karim Nabil

Karim Nabil

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princeali97 said:
Excuse me:cautious: ! i was specific.Infact i had posted exactly the same question that was given in the paper.U were'nt able to realise it.If i had posted the link to the question then u wud have answered easily by referring to the M.s :p..anyways i wasnt impressed by yor answer too.U copied exactly from the m.s.Thank you for the mark scheme (y)(y):sneaky:
Click to expand...
no comment..such a retard -_-
i don't want to have diabetes... i've exams to sit for..
well, i don't even look at the markscheme...erghh :mad:
i don't blame you for such a stupidity but blame myself for answering such a retard.
 
princeali97

princeali97

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Karim Nabil said:
no comment..such a retard -_-
i don't want to have diabetes... i've exams to sit for..
well, i don't even look at the markscheme...erghh :mad:
i don't blame you for such a stupidity but blame myself for answering such a retard.
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Retard me? or u?.U blamed me for your stupidity.Anyways i dont want to waste time on such a misunderstanding.
Im sorry from my side :).Exams are coming i dont want haters.
Best of luck.
And sorry again.(y)
 
princeali97

princeali97

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joanna omar said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s07_qp_2.pdf

Anyone Q3(b) please :)
Click to expand...
After anaphase,i,e during telophase, the chromosomes uncoil to form chromatin.Each chromatid contains one DNA molecule which will replicate itself during Interphase before the next division.Now, u can describe the DNA replication process in which you'll tell about unwinding of the DNA molecule first and complementary base pairing of each strand.And that the process is semi-conservative.And abt histones they help in packaging DNA.I hope u understood.
 
thats_me

thats_me

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princeali97

princeali97

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joanna omar said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w07_qp_2.pdf

help me out in Q2 b (ii) ANd why in (c) the graph is on the right ?
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q2b(ii)-Look,its very simple.As blood flows across respiring tissues you know that the partial pressure of O2 is low and CO2 is greater because of respiration.So it means that the tissues require O2 which haemoglobin can provide by releasing its oxygen.So,the dissociation curve tells tht as the partial pressure of O2 decreases from 6kP to 2kP, there is a sharp decrease in haemoglobin % saturation with O2, which indicates that O2 was quickly been released.And this is how 02 was delivered.
The graph will move to the right because when CO2 partial pressure is high the % saturation of haemoglobin is low( remember that :) ) So, for each partial pressure of O2,the % saturation of haemoglobin will be lower i.e (towards the right in m.s )
 
princeali97

princeali97

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thats_me said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s08_qp_2.pdf 5bi
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The surface protein is called antigen and when inserted in blood it will cause an immune response which means clonal selection will take place and B-lymphocytes specific to the antigen will start dividing by mitosis into plasma cells and memory cells.When the pathogen will enter the blood,there will be a rapid immune response carried out by memory cells which will quickly divide into plasma cells which will release antibodies.I hope u understand :)
 
thats_me

thats_me

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princeali97 said:
The surface protein is called antigen and when inserted in blood it will cause an immune response which means clonal selection will take place and B-lymphocytes specific to the antigen will start dividing by mitosis into plasma cells and memory cells.When the pathogen will enter the blood,there will be a rapid immune response carried out by memory cells which will quickly divide into plasma cells which will release antibodies.I hope u understand :)
Click to expand...
Yep got it thank you! :D
 
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