Chapter 14.5

1. Chapter 14.5 Mutated Genes and Their Protein Products AP Biology Fall 2010

2. Mutation • A gene mutation is a change in one or several bases in the nucleotide sequence of DNA • Alters the message encoded in mRNA, which can result in a change in the proteins synthesized

3. Common Gene Mutations • Spontaneous can cause sickle cell anemia • Result of a single “base pair substitution” • Places valine as the 6th amino acid in the hemoglobin chain instead of glutamate • Insertions and deletions

5. Common Gene Mutations • In a “frameshift mutation” there may be an insertion or deletion of several base pairs • Causing a misreading of the mRNA during translation

7. Common Gene Mutations • A rather dramatic mutation is that of transposable elements • Are regions of DNA that “jump” to new locations of DNA

8. Common Gene Mutations • Transposons land in genes and alter the timing, duration, or lock the genes activity together

9. How Do Mutations Arise? • Mutations occur spontaneously while DNA is being replicated, but fortunately special enzymes correct most of the mistakes • DNA polymerase and DNA ligasemay bypass or assemble a strand over the error

10. How Do Mutations Arise? • Mutations can also be caused by mutagens • Such as ionizing radiation (gamma and X-rays), ultraviolet radiation, and chemicals such as alkylating agents, which act as carcinogens

11. How Do Mutations Arise? • Nonionizing radiation changes base pairing properties by pairing thymine and to thymine, producing dimmers • Alkylating agents can transfer charged methyl or ethyl goups to reactive sites on DNA • Predisposing DNA to base pairing mistakes and mutations

12. The Proof Is in the Protein • If a mutation arises in a somatic cell, it will affect only the owner of that cell and will not be passed on to offspring • If, however, the mutation arises in a gamete, it may be passed on and thus enters the evolutionary arena • Either kind of mutation may prove to be harmful, beneficial, or neutral in its effects EWWWW!