TAKS Objective 2 TEKS 6C (Mutations)

1. TAKS Objective 2 TEKS 6C (Mutations) Applicable Text: Handouts Lesson Title: Presented by: Alexander Fedorov Composite Science Teacher

2. TAKS Objective 2 TEKS 6C (Mutations) 6C The student knows the structures and functions of nucleic acids in the mechanisms of genetics.Students should be able to identify and illustrate how changes in DNA cause mutations and evaluate the significance of these changes.

3. Chromosomal and Gene Mutations Wild Type Head Mutant Head (Antennapedia)

4. Proteins and Mutations • Proteins and Mutations: • Some proteins carry out functions within the cells of an organism. • Other proteins are exported out of the cell for other purposes.

5. Proteins and Mutations • Still other proteins are used as activators or repressors, turning genes on or off. • Therefore, a change in a cell’s proteins could have dramatic effects on the cell’s structure or function.

6. Proteins and Mutations • Changes in the DNA can change the proteins made by the cell. • A random change in the sequence of nucleotides in DNA is called a mutation. • Some mutations have little or no effect on the organism, others are harmful and very few are beneficial. Harmful mutations, Ahhhhh!!!

7. Proteins and Mutations • There are two types of mutations: 1. Chromosomal mutations 2. Gene mutations

8. Chromosomal Mutations • Chromosomal mutations are changes in the structure of a chromosome.

10. Gene Mutations • Gene mutations are errors that occur within individual genes in a chromosome. • Gene mutations can involve a single nucleotide or they can affect sections of DNA that include many nucleotides.

11. Gene Mutations • The deletion or addition of nucleotides that disrupts codons is called a frameshift mutation.

12. Gene Mutations • Because mRNA is read in codons (three-base sections) during translation, an addition or deletion of nucleotides can alter the sequence of bases, or reading frame, of the genetic message.

13. Gene Mutations What are the codons in the original reading frame? What are the codons in the shifted reading frame?

14. Gene Mutations • Recall what happens when a strand of mRNA is transcribed from DNA. • What might happen if one base is deleted from the DNA? • The transcribed mRNA would also be affected.

15. Gene Mutations • Because each mRNA codon corresponds to an amino acid, altering the codons may alter the amino acid sequence. • The end result may be an entirely different protein product. Frameshift mutations can have an enormous impact on an organism’s structure and function.

16. Gene Mutations • A change in only one nucleotide is a point mutation. • Because a point mutation affects a single codon, it tends to be far less disruptive than a frameshift mutation

17. Gene Mutations • Some amino acids are coded for by more than one codon, and substitution may simply change one codon to another codon for the same amino acid. • For example: • CUU = Leucine • Any change in the third base: CUC, CUA, CUG • still codes for the amino acid Leucine.

18. Codon Chart Third Letter

19. Gene Mutations • About 30% of all substitution mutations produce no changes in proteins. • In the remaining 70% of point mutations, changed nucleotides cause a different amino acid to be incorporated into a protein. • The resulting protein may function normally or may be defective

20. Sickle Cell Anemia • The diagram shows a point mutation and how it changes the gene from normal hemoglobin production to the production of sickle-cell hemoglobin, which in turn causes sickle-cell disease.

22. Gene Mutations • A third and very common point mutation occurs when a codon in the middle of a gene is changed to a stop codon.  • For example: UGC = Cysteine but UGA = Stop • When genes with this mutation go through protein synthesis, translation is halted before the amino acid chain is completed.

23. Cystic Fibrosis • Here is a sampling of the more than 200 different mutations that have been found in patients with cystic fibrosis • Unlike sickle-cell disease, then, no single mutation is responsible for all cases of cystic fibrosis. People with cystic fibrosis inherit two mutant genes, but the mutations need not be the same.

24. 1 Ultraviolet radiation can cause mutations in the DNA of skin cells that have been overexposed to the sun. This mutated DNA has no effect on future offspring because — A changes in skin cell DNA are homozygous recessive B mutations must occur within the RNA codons C offspring reject parental skin cells D only changes to gamete DNA can be inherited

25. 1 Ultraviolet radiation can cause mutations in the DNA of skin cells that have been overexposed to the sun. This mutated DNA has no effect on future offspring because — A changes in skin cell DNA are homozygous recessive B mutations must occur within the RNA codons C offspring reject parental skin cells D only changes to gamete DNA can be inherited

26. 2 Mutations in DNA molecules can occur when — A replication of DNA is exact B a DNA enzyme attaches to an RNA codon C RNA codons are replaced by DNA nucleotides D a change occurs in DNA nucleotide bases

27. 2 Mutations in DNA molecules can occur when — A replication of DNA is exact B a DNA enzyme attaches to an RNA codon C RNA codons are replaced by DNA nucleotides D a change occurs in DNA nucleotide bases

28. AGAUCGAGUACAUCGAGU 3 The chain above represents three codons. Which of the following changes would be expected in the amino acid chain if the mutation shown above occurred? A The amino acid sequence would be shorter than expected. B The identity of one amino acid would change. C The amino acid sequence would remain unchanged. D The identities of more than one amino acid would change.

29. AGAUCGAGUACAUCGAGU 3 The chain above represents three codons. Which of the following changes would be expected in the amino acid chain if the mutation shown above occurred? A The amino acid sequence would be shorter than expected. B The identity of one amino acid would change. C The amino acid sequence would remain unchanged. D The identities of more than one amino acid would change.

30. 4 The diagram represents the chromosomes of a person with a genetic disorder caused by nondisjunction, in which the chromosomes fail to separate properly. Which chromosome set displays nondisjunction? A 2 B 8 C 21 D 23

31. 4 The diagram represents the chromosomes of a person with a genetic disorder caused by nondisjunction, in which the chromosomes fail to separate properly. Which chromosome set displays nondisjunction? A 2 B 8 C 21 D 23

32. 5 The assembly of a messenger RNA strand that normally begins with UAC has been changed so that the newly assembled messenger RNA strand begins with UAG. Which of the following will most likely occur? A The protein will be missing the first amino acid. B The amino acids that make up the protein will all be different. C The mRNA will become attached to a ribosome. D The production of the protein will be stopped.

33. 5 The assembly of a messenger RNA strand that normally begins with UAC has been changed so that the newly assembled messenger RNA strand begins with UAG. Which of the following will most likely occur? A The protein will be missing the first amino acid. B The amino acids that make up the protein will all be different. C The mRNA will become attached to a ribosome. D The production of the protein will be stopped.

34. The End