DNA

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12 april 2020
Camila Paz Noriega
Mind Map by Camila Paz Noriega, updated more than 1 year ago
Camila Paz Noriega
Created by Camila Paz Noriega almost 5 years ago
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DNA
  1. How did scientists discover that genes are made of DNA?
    1. By the early 1900s, studies of dividing cells provided strong evidence that genes are part of chromosomes.
      1. Soon, biologist found that eukaryotic chromosomes are composed only of protein and DNA, so one of these must be the molecule of hereditary.
    2. Transformed bacteria revealed the link between genes and DNA
      1. In the late 1920s, Frederick Griffith was trying to make a vaccine to prevent bacterial pneumonia, a major cause of death at that time.
        1. Injecting antibacterial vaccines weakened but living strain into an animal may stimulate immunity against the disease- causing strains.
          1. He experimented with two strains of the bacterium Streptococcus pneumonaie.
            1. R- strain does not cause pneumonia. The mouse remains healthy.
              1. S- strain causes pneumonia. Most mouse contracts pneumonia and dies.
                1. Heat- killed S- strain does not caused pneumonia. Most mouse remains healthy.
                  1. A substance from heat-killed- S- strain can transform the harmless R-strain into deadly S-strain. Mouse contracts pneumonia and dies.
            2. Griffith hypothesized that some substances in the heat-killed S-strain changed the living, harmless R-strain bacteria into deadly S-strain, a process he called trasformation.
              1. He never discovered an effective pneumonia vaccine so this experiment was a failure. However, his experiment marked a turning point in our understanding of genetics.
              2. The Transformation Molecule is DNA
                1. in 1944 Oswaldo Avery, Colin MacLeod, and Maclyn McCarty discovered that the trasformating molecule in DNA. The insolated DNA form S-starch bacteria, mixed it with live R-strain bacteria, and produce live S-strain starin bacteria.
                  1. The protein destroying enzymes did nor prevent transformation. However, treating DNA- destroying enzymes. Therefore, they concluded that tranformation must be caused by DNA, and not by traces of protein contaminating the DNA.
                    1. DNA is the genetic material in many organisms. DNA is the hereditary molecule of certain viruses.
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