2. DNA: The Genetic Material Molecular Genetics Section 1 Griffith  Performed the first major experiment that led to the discovery of DNA as the genetic material

3. Molecular Genetics Avery  Identified the molecule that transformed the R strain of bacteria into the S strain  Concluded that when the S cells were killed, DNA was released  R bacteria incorporated this DNA into their cells and changed into S cells. DNA: The Genetic Material Section 1

4. Molecular Genetics Hershey and Chase  Used radioactive labeling to trace the DNA and protein  Concluded that the viral DNA was injected into the cell and provided the genetic information needed to produce new viruses DNA: The Genetic Material Section 1

5. Molecular Genetics DNA Structure  Nucleotides  Consist of a five-carbon sugar, a phosphate group, and a nitrogenous base DNA: The Genetic Material Section 1

6. Molecular Genetics Chargaff rule: for every adenine there is a thymine. For every guanine there is a cytosine,  Chargaff’s rule: C = G and T = A DNA: The Genetic Material Section 1

7. One team

8. Molecular Genetics X-ray Diffraction  X-ray diffraction data helped solve the structure of DNA  Indicated that DNA was a double helix DNA: The Genetic Material Section 1

9. James Watson (Left) and Francis Crick (right)

10. Molecular Genetics Watson and Crick  Built a model of the double helix that conformed to the others’ research 1. two outside strands consist of alternating deoxyribose and phosphate 2. cytosine and guanine bases pair to each other by three hydrogen bonds 3. thymine and adenine bases pair to each other by two hydrogen bonds DNA: The Genetic Material Section 1

11. Molecular Genetics DNA Structure  DNA often is compared to a twisted ladder.  Rails of the ladder are represented by the alternating deoxyribose and phosphate.  The pairs of bases (cytosine–guanine or thymine–adenine) form the steps. DNA: The Genetic Material Section 1

12. Molecular Genetics Orientation  On the top rail, the strand is said to be oriented 5′ to 3′.  The strand on the bottom runs in the opposite direction and is oriented 3′ to 5′. DNA: The Genetic Material Section 1

13. DNA: The Genetic Material Molecular Genetics Chromosome Structure  DNA coils around histones to form nucleosomes, which coil to form chromatin fibers.  The chromatin fibers supercoil to form chromosomes that are visible in the metaphase stage of mitosis. Section 1

14. Replication of DNA Molecular Genetics Semiconservative Replication  Parental strands of DNA separate. They serve as templates, and produce DNA molecules that have one strand of parental DNA and one strand of new DNA. Let’s draw Section 2

15. Molecular Genetics Steps. Of DNA Replication 1. DNA helicase, an enzyme, is responsible for unwinding and unzipping the double helix. 2. DNA polymerase, another enzyme, adds appropriate nucleotides using the original DNA as a templete. 3. The leading strand is build continuously, the lagging strand is build discontinuously in Okazaki fragments. 4. DNA ligase, another enzyme, closes up any gaps in the new DNA strand. Replication of DNA Section 2

16. Replication of DNA Molecular Genetics Comparing DNA Replication in Eukaryotes and Prokaryotes  Eukaryotic DNA unwinds in multiple areas as DNA is replicated.  In prokaryotes, the circular DNA strand is opened at one origin of replication. Section 2

17. DNA, RNA, and Protein Molecular Genetics  RNA  Contains the sugar ribose and the base uracil instead of thymine  A-U G-C  Usually is single stranded Section 3

18. Molecular Genetics Messenger RNA (mRNA)  Long strands of RNA nucleotides that are formed complementary to one strand of DNA Ribosomal RNA (rRNA)  Associates with proteins to form ribosomes in the cytoplasm Transfer RNA (tRNA)  Smaller segments of RNA nucleotides that transport amino acids to the ribosome DNA, RNA, and Protein Section 3

19.  DNA is unzipped in the nucleus and RNA polymerase binds to a specific section where an mRNA will be synthesized. Molecular Genetics Transcription  Through transcription, the DNA code is transferred to mRNA in the nucleus. DNA, RNA, and Protein Section 3

20. Molecular Genetics RNA Processing  The code on the DNA is interrupted periodically by sequences that are not in the final mRNA.  Intervening sequences are called introns.  Remaining pieces of DNA that serve as the coding sequences are called exons. DNA, RNA, and Protein Section 3 DNA and Genes

21. Molecular Genetics The Code  Experiments during the 1960s demonstrated that the DNA code was a three-base code.  The three-base code in DNA or mRNA is called a codon. DNA, RNA, and Protein Section 3

22. Molecular Genetics Translation  In translation, tRNA molecules act as the interpreters of the mRNA codon sequence.  At the middle of the folded strand, there is a three-base coding sequence called the anticodon.  Each anticodon is complementary to a codon on the mRNA. DNA, RNA, and Protein Section 3

24. Molecular Genetics DNA, RNA, and Protein Section 3

25. Molecular Genetics Mutations  A permanent change that occurs in a cell’s DNA is called a mutation.  Types of mutations  Point mutation  Insertion  Deletion Gene Regulation and Mutation Section 4

26. Molecular Genetics Gene Regulation and Mutation Section 4

27. Molecular Genetics Protein Folding and Stability  Substitutions also can lead to genetic disorders.  Can change both the folding and stability of the protein Gene Regulation and Mutation Section 4

28. Molecular Genetics Causes of Mutation  Can occur spontaneously  Chemicals and radiation also can damage DNA.  High-energy forms of radiation, such as X rays and gamma rays, are highly mutagenic. Gene Regulation and Mutation Section 4

29. Molecular Genetics Body-cell v. Sex-cell Mutation  Somatic cell mutations are not passed on to the next generation.  Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring. Gene Regulation and Mutation Section 4