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Molecular Genetics

Molecular Genetics. Chapter 12. Prokaryote Gene Regulation. Ability of an organism to control which genes are transcribed in response to the environment. operon is a section of DNA that contains the genes for the proteins needed for a specific metabolic pathway. Operator. Promoter.

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Molecular Genetics

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  1. Molecular Genetics Chapter 12 ProkaryoteGene Regulation • Ability of an organism to control which genes are transcribed in response to the environment • operon is a section of DNA that contains the genes for the proteins needed for a specific metabolic pathway. • Operator • Promoter • Regulatory gene • Genes coding for proteins

  2. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation The Trp Operon

  3. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation The Lac Operon

  4. 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.

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

  6. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation RNA Interference • RNA interference can stop the mRNA from translating its message.

  7. DNA RNA protein Molecular Genetics RNA DNA protein mRNA rRNA tRNA RNA processing transcription translation Chapter 12 12.3 Formative Questions Which shows the basic chain of events in all organisms for reading and expressing genes?

  8. Molecular Genetics Chapter 12 12.4 Formative Questions Why do eukaryotic cells need a complex control system to regulate the expression of genes?

  9. All of an organism’s cells transcribe the same Molecular Genetics 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. Chapter 12 12.4 Formative Questions

  10. Molecular Genetics Chapter 12 12.4 Formative Questions Which type of gene causes cells to become specialized in structure in function? exon Hox gene intron operon

  11. Molecular Genetics They determine number of body segments. Chapter 12 Chapter Assessment Questions Explain how Hox genes affect an organism. They determine size. They determine body plan. They determine sex.

  12. Molecular Genetics Chapter 12 Standardized Test Practice What is this process called?

  13. Molecular Genetics Chapter 12 Standardized Test Practice mRNA processing protein synthesis transcription translation

  14. Molecular Genetics Chapter 12 Standardized Test Practice How could RNA interference be used to treat diseases such as cancer and diabetes?

  15. by activating genes to produce proteins that Molecular Genetics can overcome the disease by interfering with DNA replication in cells affected by the disease by preventing the translation of mRNA into the genes associated with the disease by shutting down protein synthesis in the cells of diseased tissues Chapter 12 Standardized Test Practice

  16. Eukaryotic Gene Regulation Is the following sentence true or false? • Operons are frequently found in eukaryotes. • False

  17. Eukaryotic Gene Regulation: How are eukaryotic genes usually controlled? • Most are controlled individually and have regulatory sequences that are much more complex than those of the lac operon.

  18. Eukaryotic Gene Regulation: What is the function of the TATA box? • It seems to help position RNA polymerase by marking a point just before the point where transcription begins.

  19. Eukaryotic Gene Regulation: • Eukaryotic promoters are usually found just ____the TATA box, and they consist of a series of short ____sequences. • before • DNA

  20. Eukaryotic Gene Regulation: • List three ways in which proteins that bind to enhancer sequences of a gene can work to regulate gene expression. • They open up tightly packed chromatin. • . They help to attract RNA polymerase. • They block access to genes.

  21. Eukaryotic Gene Regulation: Why is gene regulation in eukaryotes more complex than in prokaryotes? • All of the cells in a multicellular organism carry the complete genetic code in their nucleus, but only a few of the available genes can be expressed in the appropriate cells of different tissues. • Complex regulation allows for this specificity.

  22. Development and Differentiation What role do the hox genes play in the development of an organism? • They control the differentiation of cells and tissues in the embryo.

  23. Development and Differentiation • In fruit flies, a mutation affecting the hox genes can replace a fly’s antennae with apair of legs. • The function of the hox genes in humans seems to be almost the same as it is in fruitflies.

  24. Development and Differentiation Why do common patterns of genetic control for development exist among animals?All the genes that control development have descended from the genes of common ancestors.

  25. Mutagens • Ionizing radiation (X rays) • Nonionizing radiation (UV) • Natural and synthetic chemicals

  26. Frameshift Mutations • Insertion • Extra base added into gene region • Deletion • Base removed from gene region • Both shift the reading frame • Result in many wrong amino acids

  27. Frameshift Mutation mRNA parental DNA arginine glycine tyrosine tryptophan asparagine amino acids altered mRNA DNA with base insertion altered amino- acid sequence arginine glycine leucine leucine glutamate Figure 14.12Page 234

  28. Gene mutations • Point mutations – mistakes with 1 nucleotide • Substitution of the wrong nucleotide (nitrogen base) in place of correct one • Missense mutation – substitution of a base codes for a different amino acid • Nonsense mutation – substitution of a base codes for a stop • Silent mutation – substitution of a base codes for same a.a. • Frameshift mutations – occur when a nucleotide is either inserted or deleted, altering the “trios” of nitrogen bases (More severe than point mutations because it affects all of the amino acids in the protein after that point)

  29. Chromosomal mutations • Change in the number or structure of the chromosomes • Deletion • Duplication • Inversion • Translocation

  30. Think about this! • What types of mutations are most severe? • If a mutation happens in a skin cell, will it get passed on to that person’s children? What about an egg or sperm? • In what type of cells must mutations occur in order to be passed on to offspring?

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