What do you understand by the antiparallel arrangement of DNA strands?

Explanation

### Step-by-Step Text Solution:

1. **Definition of Antiparallel**: The term "antiparallel" refers to the orientation of two strands of DNA that run parallel to each other but in opposite directions. This means that while the strands are aligned next to each other, they are oriented in such a way that one strand runs in one direction while the other runs in the opposite direction.

2. **Directionality of DNA Strands**: Each DNA strand has a directionality defined by the carbon atoms in the sugar molecule of the DNA backbone. The two ends of a DNA strand are referred to as the 5' (five prime) end and the 3' (three prime) end. In an antiparallel arrangement, one strand runs from the 5' end to the 3' end, while the complementary strand runs from the 3' end to the 5' end.

3. **Phosphate Groups**: The phosphate groups in the DNA molecule are located at the 5' end of one strand and the 3' end of the complementary strand. This arrangement is crucial for the formation of the double helix structure of DNA, as it allows for the proper pairing of nitrogenous bases between the two strands.

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