DNA, and in some cases RNA, is the primary source of heritable information Genetic Info is transmitted from one generation to the next through DNA or RNA

Genetic Information Info is stored in and passed to subsequent generations through DNA molecules and, in some cases, RNA molecules Where is it stored? Nitrogen bases How is it passed on? Mitosis and/or Meiosis

Types of Chromosomes Multiple linear chromosomes Circular Chromosomes Eukaryotic Noneukaryotic Multiple linear chromosomes Circular Chromosomes

Plasmids Prokaryotes, viruses and eukaryotes can contain plasmids Plasmids are small extra-chromosomal, double-stranded circular DNA molecules

Proof that DNA is the carrier of genetic information… The discovery of the genetic role of DNA began with the research of Fredrick Griffith in 1928. Griffith worked with 2 strains of bacterium, one pathogenic (SMOOTH) and one harmless (ROUGH) When he mixed heat- killed remains of the pathogenic strain with living cells of the harmless strain, some of the living cells became pathogenic. He called this phenomenon Transformation, now defined as a change in genotype and phenotype due to assimilation of foreign DNA.

Proof that DNA is the carrier of genetic information… In 1944, Oswald Avery, Maclyn McCarty, and Colin MacLeod announced that the transforming substance was DNA based on their extension of Griffith's study. They treated heat killed smooth bacteria to destroy 1. carbohydrates 2. lipids 3. Proteins 4. RNA 5. DNA They mixed each treatment with live rough The only treatment that did not transform was 5 – DNA- proving DNA is the transforming agent Many biologists remained skeptical.

Proof that DNA is the carrier of genetic information… In 1952, Alfred Hershey and Martha Chase preformed experiments showing that DNA is the genetic material of a phage known as T2. They designed an experiment showing that only one of the two components of T2 (DNA or protein) enters an E. coli cell during infection. They concluded that the injected DNA of the phage provides the genetic information.

Proof that DNA is the carrier of genetic information… Watson and Crick used X-ray diffraction photos from Franklin and Wilkins to conclude that DNA is made up of two antiparallel sugar- phosphate backbones. They determined that the two strands of DNA are antiparallel nature of DNA - the strands run in opposite directions. One strand runs 3' to 5' while the second strand runs 5' to 3'. They used Chargaff’s rule to determine that the nitrogen bases connected the two strands of DNA - Adenine binds to Thymine while Guanine binds to Cytosine.