D. Carbon moved in a cyclic fashion through the atmosphere and living organisms
Ans.
HD (Huntington's disease) is a genetic neurological disorder that occurs due to damage and death of brain cells. it is caused by an autosomal dominant mutation in HTT (huntingtin) gene, having a trinucleotide repeat section that makes HTT protein.
The mutation leads to an increase in this nucleotide repeat count, associated with formation of altered or mutated huntingtin protein. These altered proteins show deleterious affect on brain cells and result in Huntington's disease.
Thus, the correct answer is 'option A). a mutated gene.'
The given question says that a student has constructed a model of cellular transport using fences and several gates.
This model can be used to demonstrate the cellular transport.
The gates of the fences can be supposed as the protein pumps and the other fence demonstrates the lipid bilayer.
Let’s suppose in the fence, there are many cattles, and outside, there are less cattles, but the student open the gate and bring more cattles inside the fence. In this case, the transport of the cattles is similar to the active transport of the molecules using protein pumps. At cellular level, the energy for the active transport is provided by ATP molecules.
Now, let’s say, the student wants to feed the cattles with some nutrition rich food, which can help in maintaining the health of the cattles. The student fills his car with the cattle food and he enters inside the fence through gates. In this case, the food was not present in the fence, but was abundant in the outside environment, so, the diffusion would occur. But food cannot come self, without help of others, so, the movement is facilitated by the car, as it is done by the carrier proteins. Hence, it is an example of facilitated diffusion.
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