DNA

Genetic information is transmitted from one generation to the next through DNA and RNA. Genetic information is kept and passed to new generations through DNA molecules and sometimes RNA. DNA and RNA show specific nucleotide base pairing that is conserved through evolution. The sequence of the RNA bases, combined with the RNA molecule, determines the RNA function. mRNA carries information from the DNA to the ribosome. tRNA molecules bind specific amino acids and allow information in the mRNA to be translated to a linear peptide sequence. There have been hundreds of experiments and research studying DNA and all the components. Some of the historical contributors are, Watson, Crick, Wilkins, and Franklin on the structure of DNA. Avery-Macleod-McCarty experiments and Hershey  with the Chase experiment.  DNA replication requires DNA polymerase and many other essential cellular enzymes, occurs bidirectionally and offers  differences in the final product of the leading and lagging strands. Genetic information in retroviruses is a special case and has an alternate flow of information. From RNA to DNA, made possible by reverse transcriptase, an enzyme that copies the viral RNA genome into DNA.  This DNA integrates into the host genome and becomes transcribed and translated for the assembly of new viral progeny. DNA and RNA molecules have structural similarities and differences that define the function. Both have three components, sugar, phosphate and a nitrogenous base. Differences include, DNA contains deoxyribose, RNA contains ribose, RNA contains uracil in lieu of thymine in DNA.  Structure and function in biology result from the presence of genetic information and the correct expression of this information. The expression of the genetic material controls cell products and these products determine the metabolism and nature of the cell. Most cells within the same environment contain the same genetic makeup and instructions. Some genes are continually expressed, while the expression of most is regulated. Multicellular organisms have developmental pathways from zygote to adult but all the cells in the organism start with the same complement of DNA.