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AQA A2 Biology BIOL5 - 17th June 2015

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Original post by lauraedgar
I think its more a long the lines of DNA probes only being able to attach to single stranded DNA
Probes can be detected even when the chromosomes are not visible, as long as they have minded to the DNA.


Yes but the scientist wanted to locate the genes position on the chromosome
Original post by lauraedgar
You need single stranded DNA in order for probes to bind as there has to be exposed bases for the bases on the probes to attach to. In mitosis the DNA is being replicated so some will be single stranded


Erm was it not because chromosome become visible during prophase and anaphase during mitosis so the probe would attach to gene and be visible (you could see exactly which chromosome it attached to.... The question asked specifically for how they could identify which chromosome.
Original post by DecantedOrange
Yes but the scientist wanted to locate the genes position on the chromosome


But when in chromosomes there is nothing for the probe to attach to as there are no exposed bases
Sorry, DNA is not replicated in mitosis that happens in interphase, I think the answer was because chromosomes are only visible/DNA is only arranged in chromosomes in mitosis :/
Original post by lauraedgar
You need single stranded DNA in order for probes to bind as there has to be exposed bases for the bases on the probes to attach to. In mitosis the DNA is being replicated so some will be single stranded
Original post by lauraedgar
I think its more a long the lines of DNA probes only being able to attach to single stranded DNA
Probes can be detected even when the chromosomes are not visible, as long as they have minded to the DNA.


Pretty sure that DNA gets replicated in S phase of interphase (before mitosis happens) so the DNA during mitosis is double stranded, there's just twice as much of it in one cell.
The question even mentioned her using an optical microscope to view the chromosomes, so the reason why you'd use cells undergoing mitosis is because the chromosomes are condensed and visible during prophase.
Original post by DecantedOrange
Yes but the scientist wanted to locate the genes position on the chromosome


Plus I'm sure the scientist could only see the chromosomes in the optical microscope if the chromosomes were visible
Ok all that chromosome stuff makes sense but
HOW DOES THE PROBE BIND?
(edited 8 years ago)
Original post by lauraedgar
It's because the question was about calcium channels in the pre-synaptic membrane so you needed to talk about vesicles and acetylcholine


Ah thank you!
For those who did 10a - I struggled to find things from unit 1 and 2?

I included:
Thermoregulation in ecto and endotherms/Blood glucose regulation - talked a little about enzymes denaturing as a consequence
Reflex Arc
Survival responses
Adaptation/Natural Selection
Taxis and Kinesis
Used an out of spec topic as well about horses as a mini paragraph

Would I get full marks for breadth? Just not sure how I could have fitted much of AS in - didn't have time for immune responses
Original post by CantonHero
Frankly, I don't think it would matter. It could bind to both of them really, I put the receptor because I know antibodies do bind to protein - but I can understand why people would put growth factor.


I think they will sway towards receptor because growth factor is useful for cells that require it. So if antibodies were designed to be specific to the hormone then normal cells would be at a disadvantage. If purely designed to fit receptor then only cancerous cells are disadvantaged. Was my reasoning anyway.
will 1:0.44 be ok for ratio?
Original post by JulietR
I got 1:0.44 as well


Posted from TSR Mobile


In biology, it has to be something :1 (i think??)
Original post by studenntt
will 1:0.44 be ok for ratio?


Ratios seem to be different in every mark scheme. Which ever one they want, if you showed your working for how you got it the other way round you will definitely get a method mark
Original post by akshay.123
For 10a I wrote that testicles hang lower when warm and tight when cold, I mentioned sperm production... would that be ok for stuff out of the syllabus?
And this is not a joke.


I am laughing so hard I can't contain myself xDDDDDD

You'll get a few marks for laughter ....
Original post by akshay.123
For 10a I wrote that testicles hang lower when warm and tight when cold, I mentioned sperm production... would that be ok for stuff out of the syllabus?
And this is not a joke.


I didn't know if this was a serious suggestion haha
Original post by Hudl
Everyone saying this exam was "really easy" don't know how badly they have flopped.


It was an alright paper, although personally I think it was structured different to previous past papers in the wording of some of the questions. There were a lot of question that you could not be 100% on what the markscheme wants and also a lot of questions where there is a high possibility of getting 1 or 2 marks out of 3 depending on the markscheme. The essays were good though and overall the paper was nice, I think boundaries will increase but only a little 2/3 but not by to much more


The paper was easier than most. The boundaries will be the same.
in the essay i wrote about thermoregulation, control of heart rate pH and pressure, rods & cones, reflex arc, blood glucose, basically all unit 5 stuff :/ i feel like I'm gonna lose breadth marks but then again there are only three? I wrote in super detail about all of them so hopefully I get decent scientific knowledge marks
Original post by foureyes_
So did anyone do 10b???
If so can i get a rough idea about what you wrote? Thanks in advance :smile:


I wrote about:

Controlling population grown due to limited resources and human impact on global warmin.
Controlling human reproduction because of harmful genetic diseases
Controlling succession to conserve habitats and species and the benifits of this to humans
Controlling the growth and development of Bacteria due to the increase in antibiotic resistance
Controlling development of other mammals (hypothesised in a recently published journal that some mammals have the potential to develope and become as intelligent as humans, e.g apes and monkeys and why we should do this [human dominance])
Reply 2119
Avatar for sgollu
sgollu
for the first question i wrote ATP Phosporylase for the second one- is that even a thing looool

and for the first essay question when i got waffly i wrote about mutation in the cftr gene and how cystic fibrosis sufferers cant maintain a normal internal environment - will i lose marks for being irrelevant???
thank u :smile:

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