Which of the following is true about the structure of a doub

Which of the following is true about the structure of a double-stranded DNA molecule?

1)	Purine nucleotides always form base pairs with other purines, and pyrimidine nucleotides always form base pairs with other pyrimidines.
	2) The nitrogenous bases in one strand are held to the nitrogenous bases of the other strand by phosphodiester bonds.
	3) The nucleotides in a strand of DNA are held together by hydrogen bonds
	4) The diameter of a DNA molecule is the same along its entire length due to the specific complementary base pairing of the DNA nucleotides.

Answer:4) The diameter of a DNA molecule is the same along its entire length due to the specific complementary base pairing of the DNA nucleotides.

Explanation:

The base pairing rules for DNA are governed by the complementary base pairs: adenine (A) with thymine (T) in an A-T pairing and cytosine (C) with guanine (G) in a C-G pairing. Conversely, thymine only binds with adenine in a T-A pairing and guanine only binds with cytosine in a G-C pairing. One purine do not pair with another purine and one pyrimidine do not pair with another pyrimidine.

In order that the DNA maintain a diameter of about 2 nm across the double helix, it is necessary the smaller pyrimidines base pair with the larger purines. If two purines were to base-pair, the diameter of the double helix would be larger than 2 nm. Likewise, if two pyrimidines were to base-pair, the diameter of the double helix would be smaller than 2nm.

Which of the following is true about the structure of a double-stranded DNA molecule? Which of the following is true about the structure of a double-stranded DN

Which of the following is true about the structure of a doub

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