edexcel biology unit 2 and 3b

Use gloves when dealing with HCL or orcein
If your using orcein as your stain, make sure to avoid skin contact cuz its corrosive and highly flammable. Wear eye protection(safety goggles)
and to improve accuracy, first thing that comes to mind is repeat the experiment a few times using the same vol of HCL,stain etc, same length of root, eg:5mm
u cud even repeat it using a different root tip like broad bean.

all the best man, even im pretty nervous, im just memorising all the experiments from the CGP book and doing the past papers from june 09 to jan 12, hope it all works out. Also I asked my teacher what might come in ques 2, u know that article thing, he told me to learn the lifestyle and risk factors(heart disease and stuff) and clinical trial, Obviously im not depending on that, but he's been right before so who knows :P

Thanks man. Best answer so far. For the experiment on totipotency, what factors can we keep constant and what are possible safety measures?

well your growing a plant, so basically plants need water, light and air
so use same volume of water for all plants if your experimenting with more than one plant, use the same bulb for all plants to maintain light intesity and for air , use the same cylinder i.e to provide same amount of CO2 for all plants.
The concentration of Nitrate ions, Calcuim, Magnesium, Phosphate and all other minerals should be the same for all the plants.
For safety measures i would say since your placing the plant in agar, make sure it is sterile so that other microorganisms cannot inhibit plant growth. Also when your cutting the plant make sure you cut the part from the growing area of plant like the root or else the experiment would be futile since you wanna show Totipotency in plants.

Hope that helped

well your growing a plant, so basically plants need water, light and air
so use same volume of water for all plants if your experimenting with more than one plant, use the same bulb for all plants to maintain light intesity and for air , use the same cylinder i.e to provide same amount of CO2 for all plants.
The concentration of Nitrate ions, Calcuim, Magnesium, Phosphate and all other minerals should be the same for all the plants.
For safety measures i would say since your placing the plant in agar, make sure it is sterile so that other microorganisms cannot inhibit plant growth. Also when your cutting the plant make sure you cut the part from the growing area of plant like the root or else the experiment would be futile since you wanna show Totipotency in plants.

Hope that helped

wats a recombinant dna people!
and wats a vector ?
Suggest how cells with the resistance gene might be selected.

Suggest which tissue would be most suitable for the explants.
Explain why explants containing large quantities of xylem do not usually grow into a callus.

guyz help !!!

any answers ??

Those questions won't come. They're theory-based. This is a practical alternative paper

but dude okay wat bout this Explain why explants containing large quantities of xylem do not usually grow into a callus ?? i think it might
nd ya these in the microbial experiment


1. Record the appearance of your streak after incubation. Were you successful in obtaining single colonies of the bacterium?
2. List the different methods of sterilization, which have been used in this practical.
3. Explain why it is important:
(a) to avoid ploughing up the surface of the agar when inoculating
(b) not to seal the dishes all around with adhesive tape
(c) to invert the dishes when they are incubated.

are they tooo much ? =$

Again these don't seem like the questions they would ask you. They'd probably ask you much simpler ones, like how do you maintain sertile conditions - for which you can say you use clingfilm. I read somewhere you could put antibiotics in the agar solution to prevent growth of bacteria, but I'm not really sure. They could ask you how the clingfilm allows the explant to still grow (allows light through) and why the cotyledons shouldn't touch the agar gel (preventing contamination). Apart from all this you could say that you need to cut the seeding right under the shoot apex, where the totipotent cells are present. (They may ask you what's totipotency - the ability to develop into any type of cell). That's about it I guess.

No bro, they mentioned we don't add sugar to agar, not antibiotics.
Can we mention about temperature by water bath and pH by buffer solution as controlling factors?

I've got exactly one hour left! Any final tips?

So do you mean they do add antibiotics to the agar solution?

Where's the waterbath being used here? And the buffer solution?

No they don't. They make sure presence of contaminants are reduced by no food source therefore the absence of sugar.

Im asking you if it is :P Any controlled variables in mind for the two experiments and how to control them?

Again these don't seem like the questions they would ask you. They'd probably ask you much simpler ones, like how do you maintain sertile conditions - for which you can say you use clingfilm. I read somewhere you could put antibiotics in the agar solution to prevent growth of bacteria, but I'm not really sure. They could ask you how the clingfilm allows the explant to still grow (allows light through) and why the cotyledons shouldn't touch the agar gel (preventing contamination). Apart from all this you could say that you need to cut the seeding right under the shoot apex, where the totipotent cells are present. (They may ask you what's totipotency - the ability to develop into any type of cell). That's about it I guess.

No they don't. They make sure presence of contaminants are reduced by no food source therefore the absence of sugar.

Im asking you if it is :P Any controlled variables in mind for the two experiments and how to control them?