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A level Biology: Post your doubts here!

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Mohammed salik

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joanna omar said:
A change in a DnA or amino acid sequence leads to mutations.....Expalin then base subtituation of sickle cell anemia where T changes to A
* take comprative fig of the amino acid from diagram
ANd this mutation it could lead to altering the functin of protein and whole polypeptide changes
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Its Worth 5 Marks.. U cant Finish it this way..
Atleast i wont..! :p
 
VelaneDeBeaute

VelaneDeBeaute

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joanna omar said:
http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w11_qp_23.pdf

Explain Q4 (c)
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The question requires you to explain the relationship between the numbers of infected people and deaths.
First of all, read both graphs. The number of people infected with HIV is always greater than the number of people who died. This means that not all the people who had the virus died. It also points to the fact that not all the people with HIV contracted AIDS (which would have led to death).
Then, look at the peaks in both graphs. Most people caught the virus in 1997 but the number of deaths does not reach its peak until 2004. This means that the HIV virus takes 8-10 years to manifest and give way to infections and other opportunistic diseases.
Also, look at the decline in both curves towards the end of the graphs, especially in the 2000s. This could relate to the fact that people were aware of how the virus could be contracted so remained vigilant, and those that had the virus or contracted AIDS had access to better medication and effective health facilities.
 
VelaneDeBeaute

VelaneDeBeaute

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joanna omar

joanna omar

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VelaneDeBeaute said:
The question requires you to explain the relationship between the numbers of infected people and deaths.
First of all, read both graphs. The number of people infected with HIV is always greater than the number of people who died. This means that not all the people who had the virus died. It also points to the fact that not all the people with HIV contracted AIDS (which would have led to death).
Then, look at the peaks in both graphs. Most people caught the virus in 1997 but the number of deaths does not reach its peak until 2004. This means that the HIV virus takes 8-10 years to manifest and give way to infections and other opportunistic diseases.
Also, look at the decline in both curves towards the end of the graphs, especially in the 2000s. This could relate to the fact that people were aware of how the virus could be contracted so remained vigilant, and those that had the virus or contracted AIDS had access to better medication and effective health facilities.
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VelaneDeBeaute said:
No need to freak out if you can't draw the diagram. Simply write in words.
Or else, just check your text book for the four diagrams of mitosis (They will be all that you'd need for this question).
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THANKS A BUNCH :D
 
princeali97

princeali97

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Mohammed salik said:
I will try.. :p
In Sickel Cell anaemia Glu is replaced with val. ( u shuld know this)
If u look at Previous Part Glu is CTC.. And Val is CAC.. i chose this because they asked for One base substitutions. No coming to the answer..
A change is DNA triplet is a mutation which is cause By Substituion of A in PLace of T in DNa Template.. This in turn Alters mRNA codon and as we know Diffrent tRNA are specific to each amino acid so these Would be changed too and tRNA brings an Incorrect amino acid Val instead of Glu... This alters Polypeptide chain and Produces an Incorrect Polypeptide!
If u want u could mention Codes on mRNA and tRNA! :)
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I get it!.I was just confused why did they choose only CAC.I should have focused on the question properly cuz it said SINGLE change!.Thanks dudeee! U rock ;)
 
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