Presentation on theme: "Genetics Overview. No nuclear membrane (genetic material dispersed throughout cytoplasm) No membrane-bound organelles Simple internal structure."— Presentation transcript:
No nuclear membrane (genetic material dispersed throughout cytoplasm) No membrane-bound organelles Simple internal structure Most primitive type of cell (appeared about four billion years ago)
Staphylococcus Escherichia coli (E. coli) Streptococcus
Nuclear membrane surrounding genetic material Numerous membrane- bound organelles Complex internal structure Appeared approximately one billion years ago
Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei. Cell division and cytokinesis
Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes (including single-celled organisms) that reproduce sexually.
The Hereditary Material
1869-Friedrich Miescher, Swiss biologist He isolated various phosphate-rich chemicals from white blood cells, which he called nuclein (now nucleic acids) His discoery paved the way for the identification of DNA as the carrier of inheritance.
1930s- Joachim Hammerling Acetabularia Green algae Single-celled organism
When cap was removed new cap regeneration When foot was removed no foot regeneration Hammerling’s experiment strongly suggested that the hereditary material is located in the nucleus
Although it was clear that nucleus contains the hereditary information, the exact chemical nature was unknown Chromosomes consist of both DNA and proteins Which one contains the hereditary information?
1928-Frederick Griffith, English medical officer started experimenting with Streptococcus pneumoniae to develop a vaccine against pneumonia. he discovered what he called a transforming principle, which is today known to be DNA Sp bacterium causing pneumonia, exists in two strains
The smooth strain (S strain) had a polysaccharide capsule and was virulent when injected, causing pneumonia and killing mice in a day or two. The rough strain (R strain) did not cause pneumonia when injected into mice (it was avirulent), since it lacked a capsule.
live R strain was somehow “transformed” into the S strain Discovery showed that organisms can be genetically “re-programmed” into a slightly different version of themselves When the S bacteria were killed by heat, many substances were released (mixture contains protein, RNA, DNA, lipids, and carbohydrates What is the transforming agent?
1944-Further experiments done at The Rockefeller Institute in New York Three scientists: Oswald Avery, Colin MacLeod, and Maclyn McCarty. First, after heat-killing the S strain of bacteria, the mixture was separated into six test tubes Thus, each of the test tubes would contain the unknown “transforming agent” A different enzyme was then added to each tube
Illustration of the classic experiment demonstrating that DNA is capable of transforming harmless R strain S. pneumoniae into the pathogenic S strain.
Despite this very clear result, some scientists remained skeptical and continued to think that proteins were likely the genetic molecule. 1952-two scientists named Alfred Hershey and Martha Chase performed an entirely different type of genetic experiment to determine which molecule, DNA or protein, acted as the genetic material in phages.