biology DNA Model practical (1 Viewer)

chloescott

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hey guys for bio we have to model a DNA strciuture however were given 6 different colours of plasticine to do so, I don't understand why we need six instead of five? can someone please help!!
 

chloescott

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4 bases plus the deoxyribose sugar and the phosphate linker?
oh so would I like twists the sugar around the phosphate (two separate colours of plasticine) or cut up sections and stick it with toothpicks? I'm so confused ughhh, Thank you!
 

Eagle Mum

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oh so would I like twists the sugar around the phosphate (two separate colours of plasticine) or cut up sections and stick it with toothpicks? I'm so confused ughhh, Thank you!
I don’t think the model structure would stay up with just plasticine. It would be unfair for teachers to expect a product from only plasticine. Toothpicks, or some wire from Bunnings, wrapped in plasticine, perhaps might work.
 

chloescott

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I don’t think the model structure would stay up with just plasticine. It would be unfair for teachers to expect a product from only plasticine. Toothpicks, or some wire from Bunnings, wrapped in plasticine, perhaps might work.
i think they may be looking for the structure, so would we leave it as a ladder and twist two colour to create one strand of backbone?
 

CM_Tutor

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The backbone needs to twist around for each strand to make the double helix, alternating in colour for sugar and phosphate, and running in opposite directions (one strand has a phosphate at the top and a sugar at the bottom, the other strand has a sugar at the top and a base at the bottom). Within the helix is a parallel "ladder" of base pairs, either coloured for each of the four bases or each of the four pairs. I would use related colours for the two purines (dark and light green, say), and for the two pyrimidines.

I agree strongly with @Eagle Mum that making a model from just plasticine would be very difficult, though it depends how simplified it is. For example, could the base pairs be toothpicks covered in two colours of plasticine, a larger length for the purine and a smaller for the pyrimidine? These could then stick into the helix shown as a ribbon of alternating colours (one base pair coming off each sugar). Just a thought.
 

Eagle Mum

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I’m wary of giving the wrong advice, but I’d suggest getting the double helix backbone structure sorted out first (wires that are thick enough to hold the shape and then possibly toothpicks to keep the strands a uniform distance apart). Once you have the main structure, you can add the plasticine as per CM_T’s suggestion (Google some 3D images to help you visualise the whole model).
 

Eagle Mum

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That looks great. If the task doesn’t require a double helix, you’ve got the double strand and all the components, and their relationships, of DNA, so I’d say you’ve nailed the 2D model.
 

chloescott

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That looks great. If the task doesn’t require a double helix, you’ve got the double strand and all the components, and their relationships, of DNA, so I’d say you’ve nailed the 2D model.
oh okkk which one the first or second
 

Eagle Mum

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oh okkk which one the first or second
The second, but do check whether the task requires a double helix and that this addresses all the requirements of the task.
I’m not a teacher, though I do work in a biology field.
 

chloescott

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The second, but do check whether the task requires a double helix and that this addresses all the requirements of the task.
I’m not a teacher, though I do work in a biology field.
okayyy so is the set up correct or do I put the phosphate first in one strand and second in the other?
 

chloescott

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im doing it today
and the hydrogen bonds are correct? I'm not sure why we get 15 toothpicks
 

chloescott

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ohhh that one, however how cn we tell the difference between the covalent bonds and the hydrogen bonds, that the thing I was very confused about
 

Eagle Mum

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okayyy so is the set up correct or do I put the phosphate first in one strand and second in the other?
You seem to have already correctly followed CM_T’s advice to put “one strand has a phosphate at the top and a sugar at the bottom, the other strand has a sugar at the top and a base at the bottom” in your second model so I don’t understand your question. In the second model, your set up is correct AND you have put the phosphate first in one strand and second in the other.
 

CM_Tutor

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For the second one, to represent H-bonding, I would use two toothpicks between the A-T base pairs and three between the C-G base pairs
 

CM_Tutor

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ohhh that one, however how cn we tell the difference between the covalent bonds and the hydrogen bonds, that the thing I was very confused about
To me, you are doing that by having the lengths of toothpick in the base pair H-bonds much different from the lengths of the covalent bonds between base and sugar and between sugar and phosphate
 

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