A level Biology: Post your doubts here!

[Winx132]

Yes it is C.But I don't understand.

which part do you not understand?0.0
Look. The DNA was at first with N15 isoptpe in it right? Now that DNA is Allowed to replicate in a medium of isotope with N14( think of them as nucleotides) Now all the DNA which had N15 would replicate ..And the free nucleotide available are of only N14 since that is the medium.
YOu remember the concetp of semi conservative replication? So the N15 DNA unwinds itself and the N14 nucloetides attach themselves to the DMA molecule adn DNA N14 and 15 combine together.And since the replication period was only ONCE so only hybrid DNA would be available.
Get it?

 

[My Name]

which part do you not understand?0.0
Look. The DNA was at first with N15 isoptpe in it right? Now that DNA is Allowed to replicate in a medium of isotope with N14( think of them as nucleotides) Now all the DNA which had N15 would replicate ..And the free nucleotide available are of only N14 since that is the medium.
YOu remember the concetp of semi conservative replication? So the N15 DNA unwinds itself and the N14 nucloetides attach themselves to the DMA molecule adn DNA N14 and 15 combine together.And since the replication period was only ONCE so only hybrid DNA would be available.
Get it?

I think I get it.Thank you.

 

[Winx132]

Yes you were.
But I dont get the reason behind the answer.

Alhamdulilah kuhc tou ata hai mujhay bhi .
https://www.google.com.pk/search?q=...pvf1bujyAIVi1caCh2ysQLx#imgrc=NqlGWIbdG8rs5M:
See the middle pic that is semi conservetive replication
The dark blue in here is tha DNA with N15 isotope.
And light blue is N14 isotope
.Now consider keh it has been transfered to N14 medium and allowed to replicate just ONCE So you get the result as the below one <-- important line
And if allowed to continut so u get the one with complete blue and complter dark blue

 

[My Name]

Alhamdulilah kuhc tou ata hai mujhay bhi .
https://www.google.com.pk/search?q=semiconservative+dna+replication&espv=2&biw=1366&bih=667&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMIhpvf1bujyAIVi1caCh2ysQLx#imgrc=NqlGWIbdG8rs5M:
See the middle pic that is semi conservetive replication
The dark blue in here is tha DNA with N15 isotope.
And light blue is N14 isotope
.Now consider keh it has been transfered to N14 medium and allowed to replicate just ONCE So you get the result as the below one <-- important line
And if allowed to continut so u get the one with complete blue and complter dark blue

Alhamdulillah. Aap ka exam ho chuka ya hoga?
Thank you!

 

[Winx132]

Alhamdulillah. Aap ka exam ho chuka ya hoga?
Thank you!

hahaha..nahi mera ho chuka hai aur bohat hi ma sha Allah hua tha magar phir bhi grade acha hi a gaya.ab A 2 -___- Bohay hi zaulm hai yeh A 2 sach main ..Ajeeb Ajeeb se word wagera @_@
Apka nov session main hai kya?0.0
koi gal hi nai phen ji xD

 

[My Name]

hahaha..nahi mera ho chuka hai aur bohat hi ma sha Allah hua tha magar phir bhi grade acha hi a gaya.ab A 2 -___- Bohay hi zaulm hai yeh A 2 sach main ..Ajeeb Ajeeb se word wagera @_@
Apka nov session main hai kya?0.0
koi gal hi nai phen ji xD

Alhamdulillah!Haha haan A2 is a whole different story.
Haan IS O/N.Bas dua karain acha ho jai. XD

 

[My Name]

I dont get the question.the table.

 

[Winx132]

View attachment 57131
I dont get the question.the table.

Dekho .
sample no. 3 main uracil hai which means keh woh MRNA ka strrand hai theek? Aur us waqt base C is nil..matlab ke base C is thymine. Ab look for the other base jiski ABse C ke sath sabse zyada closeness hai and that is base B
so answer is B xD
get it?

 

[My Name]

Dekho .
sample no. 3 main uracil hai which means keh woh MRNA ka strrand hai theek? Aur us waqt base C is nil..matlab ke base C is thymine. Ab look for the other base jiski ABse C ke sath sabse zyada closeness hai and that is base B
so answer is B xD
get it?

Ohkay thank you!
I feel so dumb! <.>

 

[Winx132]

Ohkay thank you!
I feel so dumb! <.>

Your most welcome Mr./Mrs someone i dont even know xD
its okay yara.Happens alot of time.Before the exams be as dumb u can takey u get every concept right.DOnt care keh what ppl will think if u dont even get simple things.Ask away.
But this was a wierd question too xD

 

[My Name]

Your most welcome Mr./Mrs someone i dont even know xD
its okay yara.Happens alot of time.Before the exams be as dumb u can takey u get every concept right.DOnt care keh what ppl will think if u dont even get simple things.Ask away.
But this was a wierd question too xD

Its not supposed to happen when I have my exams so close. For some questions,they just looks scary to me and I panic.
Akh yeah!

 

[Winx132]

Its not supposed to happen when I have my exams so close. For some questions,they just looks scary to me and I panic.
Akh yeah!

Tell you what.There wa this guy who was really good in biology But yara his concepts JUST BEFORE exams were so idk ..Itne buray ho gae thay uske concept keh main kay bataon.Baqi yeh keh Cheer up yara.Just keep working hard Kep askin again and again uU ll get things right soon.
Who dosent panic yara?0.0 Everybody does.i panic when i see a question related to infectious disease but my sir said keh get that fear out keh u cant solve it.Once you do that then the wuestion becomes a lot easier.
Keep calm and keep going

 

[My Name]

Tell you what.There wa this guy who was really good in biology But yara his concepts JUST BEFORE exams were so idk ..Itne buray ho gae thay uske concept keh main kay bataon.Baqi yeh keh Cheer up yara.Just keep working hard Kep askin again and again uU ll get things right soon.
Who dosent panic yara?0.0 Everybody does.i panic when i see a question related to infectious disease but my sir said keh get that fear out keh u cant solve it.Once you do that then the wuestion becomes a lot easier.
Keep calm and keep going

Haw thats bad,poor him.
In sha Allah! Beware I will ask annoying doubts.
I panic when I see questions related to this N15 and N14 for P1! Infectious is fine,Alhamdulillah,so far so good.I just feel for infectious the 4 or 5 mark question I need to plan and write.
In sha Allah! Just pray for me.
I did about 86 MCQs for genetics,alot of questions were repeated.I hope my P1 has easy to score questions! In sha Allah.

 

[Winx132]

Haw thats bad,poor him.
In sha Allah! Beware I will ask annoying doubts.
I panic when I see questions related to this N15 and N14 for P1! Infectious is fine,Alhamdulillah,so far so good.I just feel for infectious the 4 or 5 mark question I need to plan and write.
In sha Allah! Just pray for me.
I did about 86 MCQs for genetics,alot of questions were repeated.I hope my P1 has easy to score questions! In sha Allah.

haha Yeah .Magar he got the exam done really good
Post them here and me is ready to answer them at all costs. However annoying they seem to be.
P1 is -___________- fazool.Magar this genetics chapter is easy !<3 too maybe. Tbh MN For P2 read the MS realllly closelye..the answer there are actually the summary of the 2 pages written in text books.That is what the examiner is demanding from you.So Give then due weight-age. They are one organized type if notes actually.
I do pray yara.You to remember me in yours.In sha Allah
yup A lot are .In my Paper i got almost 4 question repeated but the ones which were not repeated they were -_- Almost unanswerable..har kisi ne koi differnt option hi choose ki thixD Baqi Dont hope for that.Hope keh the Paper comes REALLY hard but you Understand it and do it properly.that way the threshold will be low to.<- this is what my teacher say xD

 

[My Name]

haha Yeah .Magar he got the exam done really good
Post them here and me is ready to answer them at all costs. However annoying they seem to be.
P1 is -___________- fazool.Magar this genetics chapter is easy !<3 too maybe. Tbh MN For P2 read the MS realllly closelye..the answer there are actually the summary of the 2 pages written in text books.That is what the examiner is demanding from you.So Give then due weight-age. They are one organized type if notes actually.
I do pray yara.You to remember me in yours.In sha Allah
yup A lot are .In my Paper i got almost 4 question repeated but the ones which were not repeated they were -_- Almost unanswerable..har kisi ne koi differnt option hi choose ki thixD Baqi Dont hope for that.Hope keh the Paper comes REALLY hard but you Understand it and do it properly.that way the threshold will be low to.<- this is what my teacher say xD

Alhamdulillah I hope I also do well.
Yes I will just choosing which ones to post.
Yes,I am reading the report.Haha so true!
Jazakillah khair! In sha Allah!
Ekh dont scare me Haha XD Hmm yes they say that.Bas I pray that in the end I get a GOOD GRADE! In sha Allah!

 

[My Name]

 

[SadiaMaryam]

View attachment 57128

The A tube shows the DNA strands which only contain the lighter N-14 isotopes, B shows heavier N-15 isotopes. But what are we looking for? we are actually looking for a mixture of both because one old strand(N-15) is conserved in DNA replication and new neuclotides containing N-14 are used to make the new second strand. But in D, the mixture is separate, meaning two separate strands, not combined like a real DNA double strand looks like. C seems suitable because along with being a mixture of both, it is double stranded and neucolotides of both strands in good proportion as it is in the middle.
Hope it helps

 

[goldenkatana]

Good night, greetings from Indonesia. I hope you can help me with my doubts.
Can you please help me understand what hydrostatic pressure in sieve tube elements is?
Thank you.

 

[My Name]

Good night, greetings from Indonesia. I hope you can help me with my doubts.
Can you please help me understand what hydrostatic pressure in sieve tube elements is?
Thank you.

Hi I will try to help where I can.
Hydrostatic pressure is basically the pressure exerted by the liquid.
I read this here on the site.It pretty much explains the whole thing in simple way.

In the phloem sap, in the sieve-tube elements in the leaves, there's a less negative water potential due to the presence of assimilates.<The assimilates will be the sucrose and amino acids.>
Water enters via osmosis from surrounding tissue, which results in an increase in the hydrostatic pressure.
At the sink, sucrose is unloaded, hence water potential of surrounding tissue is lowered.
Water moves out, resulting in a decrease in the hydrostatic pressure.
The pressure gradient results in a mass flow of sucrose and other substances towards the sink.

I hope that helps. Btw are you giving exam in O/N session?

 

[goldenkatana]

Hi I will try to help where I can.
Hydrostatic pressure is basically the pressure exerted by the liquid.
I read this here on the site.It pretty much explains the whole thing in simple way.

In the phloem sap, in the sieve-tube elements in the leaves, there's a less negative water potential due to the presence of assimilates.<The assimilates will be the sucrose and amino acids.>
Water enters via osmosis from surrounding tissue, which results in an increase in the hydrostatic pressure.
At the sink, sucrose is unloaded, hence water potential of surrounding tissue is lowered.
Water moves out, resulting in a decrease in the hydrostatic pressure.
The pressure gradient results in a mass flow of sucrose and other substances towards the sink.

I hope that helps. Btw are you giving exam in O/N session?

Thank you very much, you clear much of my doubts. And yes i am taking the O/N session. Do you take it as well?