I dont know why is it 3 fragments for the first question. Aslo i dont know the r

Question

I dont know why is it 3 fragments for the first question. Aslo i dont know the reasons for the other two questions' answers.

1. A linear DNA molecule is represented below. If a DNA molecule has 2 restriction sites, A and B as shown, for a specific restriction enzyme, how many fragments would be produced if the DNA is cut by that restriction enzyme? Why? * Number gach fragment. Which fragment would be the largest? Why? . 2 radient number3is thelayelest Which fragment would be the smallest? Why? .

Explanation / Answer

Imagine that we have a linear DNA molecule. This linear DNA molecule is a stretch (polynucleotide) of a sequence of purines and pyrimidines. This unique stretch of A's, T's, G's, and C's sometimes form unique sets such as GAATTC. These stretches are generally palindromic, which means that when read from 5-prime direction to 3-prime direction one on strand, or on the other, they come in the same order.
Various bacteria evolved certain DNA cutting enzymes called restriction enzymes that scope out such unique GAATTC (and others) stretches to cut the DNA at that place. This was done as a defense mechanism against introduction of genetic material by invading viruses. These sites of cutting by restriction enzymes came to be called restriction sites.
Now, we can logically expect that if a linear DNA is cut at 2 places (place A and place B) with restriction enzymes then we will end up with 3 fragments. Out of these 3 fragments the one from Cut site B to right-end terminal will the longest, while the fragment between the two cut sites will be the shortest.

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