DNA Structure and functions | A type of Nucleic Acid |
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DNA molecules have two polynucleotides,
DNA molecules have two polynucleotides, or “strands,” that wind around an imaginary axis, forming a double helix. The two sugar-phosphate backbones run in opposite 5′ → 3′ directions from each other; this arrangement is referred to as antiparallel, somewhat like a divided highway. The sugar-phosphate backbones are on the outside of the helix, and the nitrogenous bases are paired in the interior of the helix. The two strands are held together by hydrogen bonds between the paired bases.
Most DNA molecules are very long, with thousands or even millions of base pairs. For example, the one long DNA double helix in a eukaryotic chromosome includes many genes, each one a particular segment of the molecule.
In base pairing, only certain bases in the double helix are compatible with each other. Adenine (A) in one strand always pairs with thymine (T) in the other, and guanine (G) always pairs with cytosine (C). Reading the sequence
of bases along one strand of the double helix would tell us the sequence of bases along the other strand. If a stretch of one strand has the base sequence 5′-AGGTCCG-3′, then the base-pairing rules tell us that the same stretch of the other strand must have the sequence 3′-TCCAGGC-5′. The
two strands of the double helix are complementary, each the predictable counterpart of the other.
#DeoxyribonucleicAcid
Most DNA molecules are very long, with thousands or even millions of base pairs. For example, the one long DNA double helix in a eukaryotic chromosome includes many genes, each one a particular segment of the molecule.
In base pairing, only certain bases in the double helix are compatible with each other. Adenine (A) in one strand always pairs with thymine (T) in the other, and guanine (G) always pairs with cytosine (C). Reading the sequence
of bases along one strand of the double helix would tell us the sequence of bases along the other strand. If a stretch of one strand has the base sequence 5′-AGGTCCG-3′, then the base-pairing rules tell us that the same stretch of the other strand must have the sequence 3′-TCCAGGC-5′. The
two strands of the double helix are complementary, each the predictable counterpart of the other.
#DeoxyribonucleicAcid
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