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. Mutations: Gene mutations result from changes in a single gene.
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.

4. A permanent change that occurs in a cell’s DNA is called a mutation.
Chapter 12
Molecular Genetics
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. Chapter 12
Molecular Genetics

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
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. Protein Folding and Stability
Chapter 12
Molecular Genetics
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. Body-cell v. Sex-cell Mutation
Chapter 12
Molecular Genetics
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. 12.4 Gene Regulation and Mutation
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. Georgia Performance Standards
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. Prokaryote Gene Regulation
Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
Prokaryote Gene Regulation
Ability of an organism to control which genes are transcribed in response to the environment
An 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

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

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

31. Eukaryotic Gene Regulation:
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.

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. Hox Genes 12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
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. Announcements: Chapter 12 Quiz Friday ICA/HW: Mutations WS
ICA/HW: Compare and contrast gene regulation in prokaryotes and eukaryotes. (Venn Diagram)