AS Biology P1 MCQs Preparation Thread

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Trevor Jts

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Thank you very much! If possible, could you pls help me another onE?
Nov 2007 Q19
Shouldn't statement 4 chromosomes uncoil be in the first order?
 

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6Astarstudent

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Trevor Jts said:
Thank you very much! If possible, could you pls help me another onE?
Nov 2007 Q19
Shouldn't statement 4 chromosomes uncoil be in the first order?
Click to expand...
no, at prophase the chromosomes coil up
and at the end of telophase they uncoil to get ready to be replicated via semi conservative replication in interphase (which is not part of mitotic cycle)
 
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6Astarstudent

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Trevor Jts said:
Hello, anyone could explain Q21 in Nov 2006 for me?
Click to expand...
DNA is semi conservative replication, DNA has 2 strands
at the start it is all made of 15N. so 15N - 15N DNA
it grows replicate under 14N
so all 15N will pair with a 14N so 15N-14N DNA with a overall weight of 14.5, this is lighter so this is at Y after centrifuge.

and for next generation still growning under 14N
half of the original strands are now 14N, and half are 15N
so 14N combines with 14N forming 14N-14N, and 15N combines with 14N forming 15N-14N. so 50% at X which is lightest 14N-14N strand, and 50% at Y which is 14N-15N
 
enchanted era

enchanted era

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Trevor Jts said:
Hey anyone can help?
June 2004 q33
Click to expand...

Here is a table that you might find helpful. better memorize it because i m pretty sure questions from this table comes every year.
Ps- easy way to memorize about alveoli is to keep in mind that the function of alveoli is only exchange of gases. so the rest of the materials are not needed here. :)
 

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Jinosupreme

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A graft of tissue, such as skin, from a different person is usually rejected by the body.
Which statement about graft rejection is correct?
A The graft is rejected by B-lymphocytes because they make and release antibodies which react with the surface antigens on the graft cells.
B The graft is rejected by B-lymphocytes because T-lymphocytes are not stimulated to produce antibodies.
C The graft is rejected by T-lymphocytes because the graft tissue causes T-lymphocytes to release antibodies.
D The graft is rejected by T-lymphocytes because they circulate in the blood and can gather at the graft site.

Answer is D why?
 
enchanted era

enchanted era

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Jinosupreme said:
A graft of tissue, such as skin, from a different person is usually rejected by the body.
Which statement about graft rejection is correct?
A The graft is rejected by B-lymphocytes because they make and release antibodies which react with the surface antigens on the graft cells.
B The graft is rejected by B-lymphocytes because T-lymphocytes are not stimulated to produce antibodies.
C The graft is rejected by T-lymphocytes because the graft tissue causes T-lymphocytes to release antibodies.
D The graft is rejected by T-lymphocytes because they circulate in the blood and can gather at the graft site.

Answer is D why?
Click to expand...

its a fact, memorize it :p elaborating and finding logical explanations will lead to something beyond our level i guess :p. the fact is t-lymphocytes are responsible of dealing with graft tissues may be because they got the killer cells and b-lymphocytes releases antibodies which got no complementary binding sites to the antigens of graft cells :/
 
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Rosy S

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enchanted era said:
convert all the units into metre (reduces confusion)
so, 750nm= 7.5x10-7
and 15um= 1.5x10-5
then just divide them 1.5x10-5 / 7.5x10-7 = 20
Click to expand...
enchanted era said:
Here is a table that you might find helpful. better memorize it because i m pretty sure questions from this table comes every year.
Ps- easy way to memorize about alveoli is to keep in mind that the function of alveoli is only exchange of gases. so the rest of the materials are not needed here. :)
Click to expand...

That Table was really helpful do you have such kind of other useful information??
 
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