However, sometimes the repair is unsuccessful, resulting in different proteins being created. Most of the time when this happens the DNA is able to fix itself and return the original base to the sequence. For example, in the sequence AATTGGCC, a mutation may cause the second T to change to a G. A mutation is a change in the sequence of the nitrogen bases. At this time it is possible a mutation may occur. Adenine forms hydrogen bonds (or base pairs) with thymine, and guanine base pairs with cytosine.ĭuring DNA replication, each strand is copied, resulting in a daughter DNA double helix containing one parental DNA strand and a newly synthesized strand. Covalent bonds occur within each linear strand and strongly bond the. The phosphate backbone is located on the outside, and the bases are in the middle. The DNA double helix is held together by two types of bonds, covalent and hydrogen. If the sequence of one strand is AATTGGCC, the complementary strand would have the sequence TTAACCGG.Īntiparallel StrandsIn a double stranded DNA molecule, the two strands run antiparallel to one another so that one strand runs 5′ to 3′ and the other 3′ to 5′. This is known as the base complementary rule because the DNA strands are complementary to each other. This means Adenine pair with Thymine, and Guanine pairs with Cytosine. For example, a certain purine can only pair with a certain pyrimidine. Only certain types of base pairing are allowed. Each base from one strand interacts via hydrogen bonding with a base from the opposing strand. The phosphate backbone (indicated by the curvy lines) is on the outside, and the bases are on the inside. This antiparallel orientation is important to DNA replication and in many nucleic acid interactions.ĭNA is a Double HelixNative DNA is an antiparallel double helix. The two strands of the helix run in opposite directions, so that the 5′ carbon end of one strand faces the 3′ carbon end of its matching strand. The nitrogenous bases are stacked in the interior in pairs, like the steps of a staircase the pairs are bound to each other by hydrogen bonds. antiparallelThe nature of the opposite orientations of the two strands of DNA or two beta strands that comprise a protein's secondary structureĭNA has a double-helix structure, with sugar and phosphate on the outside of the helix, forming the sugar-phosphate backbone of the DNA.mutationany heritable change of the base-pair sequence of genetic material.Due to the base pairing, the DNA strands are complementary to each other, run in opposite directions, and are called antiparallel strands.The nitrogen bases can only pair in a certain way: A pairing with T and C pairing with G.

The sugar and phosphate make up the backbone, while the nitrogen bases are found in the center and hold the two strands together.The structure of DNA is called a double helix, which looks like a twisted staircase.

Double helix dna