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Molecular Genetics

Molecular Genetics. Chapter 12. 12.1 DNA: The Genetic Material. DNA Structure. Nucleotides. Consist of a five-carbon sugar, a phosphate group, and a nitrogenous base. Molecular Genetics. Chapter 12. 12.1 DNA: The Genetic Material. Chargaff. Chargaff’s rule: C = G and T = A.

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Molecular Genetics

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  1. Molecular Genetics Chapter 12 12.1 DNA: The Genetic Material DNA Structure • Nucleotides • Consist of a five-carbon sugar, a phosphate group, and a nitrogenous base

  2. Molecular Genetics Chapter 12 12.1 DNA: The Genetic Material Chargaff • Chargaff’s rule: C = G and T = A

  3. Molecular Genetics Chapter 12 12.1 DNA: The Genetic Material X-ray Diffraction • X-ray diffraction data helped solve the structure of DNA • Indicated that DNA was a double helix

  4. Molecular Genetics Chapter 12 12.1 DNA: The Genetic Material Watson and Crick • Built a model of the double helix that matched the others’ research two outside strands consist of alternating sugar 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

  5. Molecular Genetics Chapter 12 12.1 DNA: The Genetic Material DNA Structure • DNA often is compared to a twisted ladder. • Sides of the ladder are represented by the alternating sugar and phosphate. • The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.

  6. Molecular Genetics Chapter 12 12.1 DNA: The Genetic Material Chromosome Structure • The chromatin fibers supercoil to form chromosomes that are visible in the metaphase stage of mitosis.

  7. Molecular Genetics Chapter 12 12.2 Replication of DNA Semiconservative Replication • Original strands of DNA separate • Serve as templates • Produce 2 new DNA molecules • Each have one strand of original DNA and one strand of new DNA.

  8. Molecular Genetics Chapter 12 12.2 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 spot.

  9. Molecular Genetics Chapter 12 12.3 DNA, RNA, and Protein Central Dogma • DNA RNA Protein • RNA • Contains the sugar ribose and the base uracil • Usually is single stranded

  10. Molecular Genetics Chapter 12 12.3 DNA, RNA, and Protein Messenger RNA (mRNA) • Long strands of RNA that carry DNA info from the nucleus to the cytoplasm Ribosomal RNA (rRNA) • Forms ribosomes in the cytoplasm Transfer RNA (tRNA) • Smaller segments of RNA that bring amino acids to the ribosome

  11. Molecular Genetics Chapter 12 12.3 DNA, RNA, and Protein

  12. Molecular Genetics Chapter 12 12.3 DNA, RNA, and Protein Transcription • DNA code is transferred to mRNA in the nucleus.

  13. Molecular Genetics Chapter 12 12.3 DNA, RNA, and Protein The Code • Experiments during the 1960s demonstrated that the DNA code was a three-base code. • The three-base code is called a codon.

  14. Molecular Genetics Chapter 12 12.3 DNA, RNA, and Protein Translation • tRNA molecules interpret the mRNA codon sequence. • At the bottom of the tRNA, there is a three-base sequence called the anticodon. • Each anticodon matches a codon on the mRNA.

  15. Molecular Genetics Chapter 12

  16. Molecular Genetics Chapter 12 12.4 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.

  17. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation Hox Genes • Hox genes are responsible for the general body pattern of most animals.

  18. Molecular Genetics Chapter 12 12.4 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

  19. Molecular Genetics Chapter 12

  20. Molecular Genetics Chapter 12 12.4 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.

  21. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation Body-cell v. Sex-cell Mutation • Body 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.

  22. A B C D Molecular Genetics Chapter 12 FQ 2 12.1 Formative Questions 1. What is the base-pairing rule for purines and pyrimidines in the DNA molecule? A—G and C—T A—T and C—G C—A and G—T C—U and A—G

  23. A B C D Molecular Genetics Chapter 12 FQ 3 12.1 Formative Questions 2. What are chromosomes composed of? chromatin and histones DNA and protein DNA and lipids protein and centromeres

  24. A B C D Molecular Genetics Chapter 12 FQ 6 12.3 Formative Questions 3. Which shows the basic chain of events in all organisms for reading and expressing genes? DNA  RNA protein RNA DNA protein mRNA rRNA tRNA RNA processing transcription translation

  25. A B C D Molecular Genetics Chapter 12 FQ 7 12.3 Formative Questions 4. In the RNA molecule, uracil replaces _______. adenine cytosine purine thymine

  26. A B C D Molecular Genetics A. B. C. D. Chapter 12 FQ 8 12.3 Formative Questions 5. Which diagram shows messenger RNA (mRNA)?

  27. A B C D Molecular Genetics Chapter 12 FQ 10 12.4 Formative Questions 6. Why do eukaryotic cells need a complex control system to regulate the expression of genes? All of an organism’s cells transcribe the same genes. Expression of incorrect genes can lead to mutations. Certain genes are expressed more frequently than others are. Different genes are expressed at different times in an organism’s lifetime.

  28. A B C D Molecular Genetics Chapter 12 FQ 11 12.4 Formative Questions 7. Which type of gene causes cells to become specialized in structure in function? exon Hox gene intron operon

  29. A B C D Molecular Genetics Chapter 12 FQ 13 12.4 Formative Questions 8. Which is the most highly mutagenic? chemicals in food cigarette smoke ultraviolet radiation X rays

  30. A B C D Molecular Genetics Chapter 12 CAQ 2 Chapter Assessment Questions 9. Explain how Hox genes affect an organism. They determine size. They determine body plan. They determine sex. They determine number of body segments.

  31. Molecular Genetics Answer: A mutagen in a body cell becomes part of the of the genetic sequence in that cell and in future daughter cells. The cell may die or simply not perform its normal function. These mutations are not passed on to the next generation. When mutations occur in sex cells, they will be present in every cell of the offspring. Chapter 12 CAQ 3 Chapter Assessment Questions 10. Explain the difference between body-cell and sex-cell mutation.

  32. A B C D Molecular Genetics Chapter 12 STP 2 Standardized Test Practice 11. What is this process called? mRNA processing protein synthesis transcription translation

  33. A B C D Molecular Genetics TTCAGG TTCTGG Chapter 12 STP 3 Standardized Test Practice 12. What type of mutation results in this change in the DNA sequence? deletion frameshift insertion substitution

  34. A B Molecular Genetics Chapter 12 STP 5 Standardized Test Practice 13. The structure of a protein can be altered dramatically by the exchange of a single amino acid for another. • True • False

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