DNA Overview Historical Scientific Events that led to the discovery of DNA as the molecule of heredity.

What have we done and know so far? Cell  organelles Cell  organelles Nucleus  chromosomes  DNA Nucleus  chromosomes  DNA During interphase (S –phase) DNA replicates During interphase (S –phase) DNA replicates Mitosis allows for new cells with the exact copy of DNA Mitosis allows for new cells with the exact copy of DNA At this point, what future questions might you have about what we know and what it means to be who we are?

Objectives Describe the composition and structure of a DNA molecule Describe the composition and structure of a DNA molecule Summarize the process of DNA replication and evaluate the importance of correcting DNA errors Summarize the process of DNA replication and evaluate the importance of correcting DNA errors Explain the connection between DNA and RNA in protein synthesis Explain the connection between DNA and RNA in protein synthesis Summarize the processes of transcription and translation and infer the consequences of errors during these events Summarize the processes of transcription and translation and infer the consequences of errors during these events Recognize the role and significance of the genetic code Recognize the role and significance of the genetic code Explain why proteins are important to biological systems and discuss why the regulation of gene expression is significant in living organisms Explain why proteins are important to biological systems and discuss why the regulation of gene expression is significant in living organisms Have an understanding of mutations and their effects on living organisms Have an understanding of mutations and their effects on living organisms Explain the contributions of various scientists Explain the contributions of various scientists

Genetic Material DNA or Protein? What is the material that is passed on from generation to generation? What is the material that is passed on from generation to generation? 3 key experiments 3 key experiments –Frederick Griffith and transformation –Oswald Avery –Alfred Hershey and Martha Chase

Griffith showed: Griffith showed: –genetic information could change – this change could be passed on from generation to generation. Avery believed that DNA was the information that changed and is passed on Avery believed that DNA was the information that changed and is passed on Hershey and Chase backed Avery’s theory and showed that indeed the information is DNA Hershey and Chase backed Avery’s theory and showed that indeed the information is DNA

Frederick Griffith’s experiments in 1928 suggested: Frederick Griffith’s experiments in 1928 suggested:  The harmless R strain bacteria had acquired parts of the harmful S strain, causing it to change and kill the mouse.  In addition, the R strain of bacteria was able to pass on the deadly trait to the next generation.  In addition, the R strain of bacteria was able to pass on the deadly trait to the next generation.  The change was permanent and inheritable. Avery believed the change was caused by DNA and not protein Avery believed the change was caused by DNA and not protein

Hershey and Chase experiment Used viruses Used viruses –inject their genetic material into their hosts. Viruses are made of protein and DNA and both parts were “tagged” Viruses are made of protein and DNA and both parts were “tagged” –Protein was tagged with radioactive sulfur –DNA was tagged with radioactive phosphorous In the hosts, the radioactive phosphorous was found In the hosts, the radioactive phosphorous was found - It was the DNA that was injected.

Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) DNA STRUCTURE Nucleotide Sugar-phosphate backbone