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Genetics Overview.  No nuclear membrane (genetic material dispersed throughout cytoplasm)  No membrane-bound organelles  Simple internal structure.

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Presentation on theme: "Genetics Overview.  No nuclear membrane (genetic material dispersed throughout cytoplasm)  No membrane-bound organelles  Simple internal structure."— Presentation transcript:

1 Genetics Overview

2  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)

3  Staphylococcus  Escherichia coli (E. coli)  Streptococcus

4  Nuclear membrane surrounding genetic material  Numerous membrane- bound organelles  Complex internal structure  Appeared approximately one billion years ago

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6 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

7 Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes (including single-celled organisms) that reproduce sexually.

8 The Hereditary Material

9  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.

10  1930s- Joachim Hammerling  Acetabularia  Green algae  Single-celled organism

11  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

12  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?

13  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

14  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.

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16  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?

17  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

18 Illustration of the classic experiment demonstrating that DNA is capable of transforming harmless R strain S. pneumoniae into the pathogenic S strain.

19  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.

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