6.1 DNA and RNA Structure

Describe the structures involved in passing hereditary information from one generation to the next.

• Genetic information is stored in and passed to subsequent generations through DNA molecules and, in some cases, RNA molecules.
  • i. Prokaryotic organisms typically have cir cular chromosomes.
  • ii. Eukaryotic organisms typically have multiple linear chr omosomes that are comprised of DNA. These chromosomes are condensed using histones and associated proteins.
• Prokaryotes and eukaryotes can contain plasmids, which are extra-chromosomal circular molecules of DNA.

Describe the characteristics of DNA that allow it to be used as hereditary material.

• Nucleic acids exhibit specific nucleotide base pairing that is conserved through evolution.
  • i. Purines (guanine and adenine) have a double ring structur e.
  • ii. Pyrimidines (cytosine, thymine, and uracil) ha ve a single ring structure.
  • iii. Purines pair with pyrimidines: adenine with thymine (or uracil in RNA) and guanine with cytosine.