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Molecular Genetics

Molecular Genetics. Section 1: DNA: The Genetic Material. Section 2: Replication of DNA. Section 3: DNA, RNA, and Protein. Section 4: Gene Regulation and Mutation. Molecular Genetics. Section 1. DNA: Discovery. Frederick Griffith – 1928 British Bacteriologist.

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Molecular Genetics

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  1. Molecular Genetics Section 1: DNA: The Genetic Material Section2: Replication of DNA Section 3: DNA, RNA, and Protein Section 4: Gene Regulation and Mutation

  2. Molecular Genetics Section 1 DNA: Discovery Frederick Griffith – 1928 British Bacteriologist • Performed the first major experiment that led to the discovery of DNA as the genetic material • REFUTED THAT PROTEIN WAS THE GENETIC MATERIAL – ANOTHER LARGE MOLECULE –DNA CARRIED GENETIC INFO

  3. Molecular Genetics Section 1 DNA: The Genetic Material Oswald Avery – 1944 Microbiologist • 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. • VERIFIED GRIFFITH’S EXPERIMENT

  4. Molecular Genetics Section 1 DNA: The Genetic Material Hershey and Chase - 1952 • 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 • CONFIRMED THAT DNA IS THE GENETIC MATERIAL

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

  6. Molecular Genetics Section 1

  7. Molecular Genetics Section 1 DNA: The Genetic Material Erwin Chargaff -1950 • Chargaff’s rule: C = G and T = A

  8. Molecular Genetics Section 1 DNA: The Genetic Material X-ray Diffraction • Rosalind Franklin - 1951 • X-ray diffraction data helped solve the structure of DNA • Indicated that DNA was a double helix

  9. Molecular Genetics Section 1 DNA: The Genetic Material Watson and Crick - 1953 • Built a model of the double helix that conformed to the others’ research two outside strands consist of alternating deoxyribose and phosphate cytosine and guanine bases pair to each other by three hydrogen bonds thymine and adenine bases pair to each other by two hydrogen bonds

  10. Cambridge University, Cambridge Kings College, London Linus Pauling CalTech

  11. Molecular Genetics Section 1 DNA: The Genetic Material 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.

  12. Molecular Genetics Section 1 DNA: The Genetic Material 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′.

  13. Molecular Genetics Section 1 DNA: The Genetic Material 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.

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

  15. What is the complementary strand for the DNA segment A C T G G A ?

  16. Molecular Genetics Section 2 Replication of DNA Unwinding • DNA helicase, an enzyme, is responsible for unwinding and unzipping the double helix. • RNA primase adds a short segment of RNA, called an RNA primer, on each DNA strand.

  17. Molecular Genetics Section 2 Replication of DNA Base pairing • DNA polymerase continues adding appropriate nucleotides to the chain by adding to the 3′ end of the new DNA strand.

  18. Molecular Genetics Section 2

  19. Molecular Genetics Section 2 Replication of DNA • One strand is called the leading strand and is elongated as the DNA unwinds. • The other strand of DNA, called the lagging strand, elongates away from the replication fork. • The lagging strand is synthesized discontinuously into small segments, called Okazaki fragments.

  20. Molecular Genetics Section 2 Replication of DNA Joining • DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides. • DNA ligase links the two sections.

  21. Molecular Genetics Section 2 Replication of DNA 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.

  22. Molecular Genetics Section 3

  23. Molecular Genetics Section 3 DNA, RNA, and Protein • RNA • Contains the sugar ribose and the base uracil instead of thymine • Usually is single stranded

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

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

  26. Transcribe A C A G G A

  27. Molecular Genetics Section 3 DNA, RNA, and Protein 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 and Genes

  28. Molecular Genetics Section 3 DNA, RNA, and Protein The mRNA 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.

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

  30. According to the mRNA Genetic Code which amino acid sequence would most likely be determined by a section of DNA molecule with the base sequence: • A-C-A-G-G-A-T-C-A

  31. Molecular Genetics Section 3 DNA, RNA, and Protein One Gene—One Enzyme • The Beadle and Tatum (1941) experiment showed that one gene codes for one enzyme. We now know that one gene codes for one polypeptide.

  32. Molecular Genetics Section 4 Gene Regulation and Mutation Eukaryote Gene Regulation • Controlling transcription • Transcription factors ensure that a gene is used at the right time and that proteins are made in the right amounts • The complex structure of eukaryotic DNA also regulates transcription.

  33. Molecular Genetics Section 4 Gene Regulation and Mutation Hox Genes • Hox genes are responsible for the general body pattern of most animals.

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

  35. Molecular Genetics Section 4 THE BIG RAT CAT ATE THE WET BAT

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

  37. Molecular Genetics Section 4 Gene Regulation and Mutation 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.

  38. Molecular Genetics Section 4 Gene Regulation and Mutation 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.

  39. A B C D Molecular Genetics Chapter CDQ 1 Chapter Diagnostic Questions Which scientist(s) definitively proved that DNA transfers genetic material? Watson and Crick Mendel Hershey and Chase Avery

  40. A B C D Molecular Genetics Chapter CDQ 1 Chapter Diagnostic Questions During which stage of the cell cycle does DNA replication take place? Growth Prophase Synthesis Mitosis

  41. A B C D Molecular Genetics Chapter CDQ 2 Chapter Diagnostic Questions Name the small segments of the lagging DNA strand. ligase Okazaki fragments micro RNA helicase

  42. A B C D Molecular Genetics Chapter CDQ 3 Chapter Diagnostic Questions Which is not true of RNA? It contains the sugar ribose. It contains the base uracil. It is single-stranded. It contains a phosphate.

  43. A B C D Molecular Genetics Chapter FQ 1 Section 1 Formative Questions The experiments of Avery, Hershey and Chase provided evidence that the carrier of genetic information is _______. carbohydrate DNA lipid protein

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