There are two antiparallel strands of DNA so that the five-prime end of one strand will face the three-prime end of another strand. Remember, the three-prime end has the free hydroxyl group and the five-prime end has the free phosphate group. The outside of the double helix has the deoxyribose molecule and the phosphodiester bond, while the inside of the double helix has the nitrogenous bases that connect to one another through hydrogen bonding. There are ten bases per turn of the helix. There are major grooves and minor grooves that are made from the asymmetry between the base pairs. The fact that thymine goes together with adenine and that guanine goes together with cytosine means that these are considered complementary base pairs and matches completely with Chargaff’s rule. Some complementary base pairs, namely A and T, have two hydrogen bonds, while C and G have three hydrogen bonds between the two molecules. The strands will separate at higher temperatures and in the presence of certain chemicals. This is called denaturing the DNA. The single strands of DNA can be put together again if the circumstances are right. Because of the differences in the number of hydrogen bonds, the DNA with high GC content is harder to break than those that are high in AT. DNA will store the genetic material of the cell. With vertical gene transfer, the mother cell transfers the genetic material to the daughter cells. DNA is replicated anytime the cell divides to make daughter cells. This is basically the only function that DNA has with regard to the cell. There are no structural elements to the DNA molecule.
RNA STRUCTURE AND FUNCTION Ribonucleic acid or RNA is very similar to DNA but it is generally single-stranded, has much shorter strands, and contains ribose instead of deoxyribose. RNA is made from ribonucleotides and is linked together via phosphodiester bonds, just as is seen in DNA. The nitrogenous bases are different with RNA. There is adenine, guanine, and cytosine like in DNA but the uracil replaces thymine that is seen in DNA. DNA is somewhat more stable than RNA so it is better than RNA in keeping genetic information. Adenine matches with uracil in the RNA molecule.
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