Mutations

1. Mutations Georgia Standard: Describe the relationships between mutations in DNA and potential appearance of new traits. Identify the types of mutations that can alter DNA. Explain the role of DNA in storing and transmitting cellular information. • Essential Question: • What is the role of mutation in producing variation? • How does a cell make protein?

2. Warm-up: • Copy the following information about Protein X: Methionine—Phenylalanine—Tryptophan—Asparagine—Isoleucine—STOP. • Use the genetic code in your textbook to determine one possible sequence of RNA to code for this information. Write this code below the description of Protein X. Below this, write the DNA code that would produce this RNA sequence. • Now, cause a mutation in the gene sequence that you just determined by deleting the fourth base in the DNA sequence. Write this new sequence. • Write the new RNA sequence that would be produced. Below that, write the amino acid sequence that would result from this mutation in your gene. Call this Protein Y. • Did this single deletion cause much change in your protein? Explain your answer.

3. Changes in the DNA sequence that affect genetic information. Gene mutations result from changes in a single gene. Chromosomal mutations involve changes in whole chromosomes. Mutations:

4. 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

5. Molecular Genetics Chapter 12

6. Gene Mutations: • Point mutation = affects one nucleotide • Insertion • Deletion • Substitution • Cause frameshift mutations: they shift the reading frame of a genetic message. • video

7. Gene Mutations:Substitution, Insertion, and Deletion Deletion Insertion Substitution Go to Section:

8. Chromosomal Mutations: Changes in the number or structure of chromosomes Result: Change the locations of genes on chromosomes or the number of copies of some genes. Ex: Down Syndrome

9. Types of Chromosomal Mutations: • Deletion = loss of all or part of a chromosome • Duplication = a segment of chromosome is repeated • Inversion = chromosome is inverted in reverse of its usual direction • Translocation = part of a chromosome breaks off and attaches to another, nonhomologous, chromosome • video

10. Chromosomal Mutations Section 12-4 Deletion Duplication Inversion Translocation Go to Section:

11. Molecular Genetics Chapter 12 12.4 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

12. Molecular Genetics Chapter 12 12.4 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.

13. Molecular Genetics 12.4 Gene Regulation and Mutation

14. What Causes These Mutations? • High energy radiation: x-rays, ultraviolet light, gamma rays • Chemicals • Environmental Factors • Can occur spontaneously

15. Good Mutations: • Mutations cause diversity of genes in the living world • This diversity makes evolution and natural selection possible. • Mutations create the different alleles needed for genetic research

16. Checkpoint Questions: • What is a gene mutation? What is a chromosomal mutation? 2. What is a point mutation? 3. What are two kinds of frameshift mutations? 4. What are four types of chromosomal mutations? 5. The effects of a mutation are not always visible. How might a biologist determine whether a mutation has occurred and, if so, what type of mutation it is?

17. Gene Regulation: • Georgia Performance Standards • Compare and contrast gene regulation in eukaryotes and prokaryotes. Essential Question: How does a cell know when to stop making a protein? How does the cell determine which genes will be expressed and which will remain “silent”?

18. Gene Regulation: • Only a fraction of the genes in a cell are expressed at any given time. • An expressed gene is a gene that is transcribed into RNA.

19. Warm-up: 1. Do you think that cells produce all the proteins for which the DNA (genes) code? Why or why not? How do the proteins made affect the type and function of cells? 2. Consider what you now know about genes and protein synthesis. What might be some ways that a cell has control over the proteins it produces? 3. What type(s) of organic compounds are most likely the ones that help to regulate protein synthesis? Justify your answer.

20. Gene Regulation: • In fact, cells are filled with DNA-binding proteins that attach to specific DNA sequences and help to regulate gene expression. • Promoters • Start and stop sequences

21. Typical Gene Structure Section 12-5 Promoter(RNA polymerase binding site) Regulatory sites DNA strand Start transcription Stop transcription Go to Section:

22. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation Prokaryote Gene Regulation • Ability of an organism to control which genes are transcribed in response to the environment • Anoperon 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

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

24. Prokaryotic Gene Regulation Ex: • E.Coli bateria: • Operons operate together to make a needed protein for a certain metabolic pathway. • Because these genes must be expressed in order for the bacterium to be able to use the sugar lactose as a food, they are called the lac operon. • The lac genes are turned off by repressors and turned on by the presence of lactose.

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

26. Function of the Lac Repressor • The lac genes in E. coli are turned off by repressors and turned on by the presence of lactose. • When lactose is not present, the repressor binds to the operator region, preventing RNA polymerase from beginning transcription. • Lactose causes the repressor to be released from the operator region.

27. Molecular Genetics Chapter 12

28. 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.

29. Eukaryotic Gene Regulation: • Genes are regulated in a variety of ways by enhancer sequences located before the beginning of transcription. • An enormous number of proteins can bind to different enhancer sequences, which is why eukaryotic gene regulation is so complex. • Some of these DNA-binding proteins enhance transcription by opening up tightly packed chromatin. Others help to attract RNA polymerase.

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

31. Operons are generally not found in eukaryotes.   Most eukaryotic genes are controlled individually and have regulatory sequences that are much more complex One of the most interesting is a short region of DNA about 30 base pairs long, with a sequence of TATATA or TATAAA, before the start of transcription. The “TATA”box seems to help position RNA polymerase by marking the promotor (a point just before the point at which transcription begins). Eukaryotic promoters are usually found just before the TATA box, and they consist of a series of short DNA sequences. Eukaryotic Gene Regulation:

32. Introns & Exons:

33. Eukaryotic Gene Regulation Eukaryotic genes are more complex than prokaryotic genes. Many eukaryotic genes include a sequence called the TATA box that may help position RNA polymerase.

34. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation Hox Genes • Hox genes are responsible for the general body pattern of most animals. • A mutation in one of these “master control genes” can completely change the organs that develop in specific parts of the body. • Genes descended from common ancestors.

35. Hox Genes In fruit flies, a series of hox genes along a chromosome determines the basic structure of the fly’s body. Mice have very similar genes on four different chromosomes.

36. Why is gene regulation in eukaryotes more complex than in prokaryotes? • Cell specialization requires genetic specialization • multicellular organism = eukaryotes • Unicellular organism = prokaryotes (no cell specialization) • Only a tiny fraction of the available genes needs to be expressed in cells of different tissues throughout the body. • The complexity of gene regulation in eukaryotes makes this specificity possible.

37. Checkpoint Questions: • How is the lac operon regulated? • Describe how most eukaryotic genes are controlled. 3. What is a promoter? 4. Why are only a limited number of genes expressed in each cell of a multicellular eukaryote? 5. How is the way hox genes are expressed in mice similar to the way they are expressed in fruit flies? How is it different?

38. Chapter 12 Quiz Friday ICA/HW: Mutations WS ICA/HW: Compare and contrast gene regulation in prokaryotes and eukaryotes. (Venn Diagram) Announcements: