DNA Structure

Why does a DNA molecule consist of two strands? The primary function of DNA is to store and transmit genetic information. To accomplish this function DNA must have two properties. It must be chemically stable so as to reduce the possibility of damage. DNA must also be capable of copying the information it contains. The two-stranded structure of DNA gives it both of these properties. The nucleotide sequence contains the information found in DNA. The nucleotides connect the two strands through hydrogen bonds. Because each nucleotide has a unique complimentary nucleotide, each strand contains all the information required to synthesize a new DNA molecule. The double stranded structure also makes the molecule more stable.

View the animation below, then complete the quiz to test your knowledge of the concept.


1	The correct structure of DNA components can be presented as

		A)	phosphate–base–sugar.
		B)	phosphate–sugar–base.
		C)	base–phosphate–sugar.
		D)	phosphate–sugar–phosphate–base.
		E)	base–sugar–phosphate–base.

2	Which of the following is a characteristic of double-stranded DNA?

		A)	2 nanometers in width
		B)	10 base pairs per turn
		C)	0.34 nanometers per basepair
		D)	A and B
		E)	A, B and C

3	Which of the following DNA molecules is the most stable?

		A)	CTGCATAC GACGTATG
		B)	GAAATTTC CTTTAAAG
		C)	AGTCGAAT TCAGCTTA
		D)	GCGTGCAC CGCACGTG
		E)	GGATCCTG CCTAGGAC

4	Doubled-stranded DNA consists of two antiparallel strands, meaning that one strand is oriented in the 5’ to 3’ direction, while the other is oriented in the 3’ to 5’ direction.

		A)	True
		B)	False

5	Asymmetrical spacing of the backbones of the DNA double helix generates major and minor grooves.

		A)	True
		B)	False

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