Welcome 1/26-27/16  In your journal, write a paragraph explain what a genetic code is and the purpose of transcription and translation.  Turn in Snork DNA and Vocab  Notes on Mutations  Mutations Practice problems  Homefun: study for your quiz  Reminder: Next Monday and Tuesday project is due!

Mutations

Learning Objectives  Define mutations and describe the different types of mutations.  Describe the effects mutations can have on genes.

Mutations Mutations are heritable changes in genetic information.

Types of Mutations Mutations fall into two basic categories:  Gene mutations  Chromosomal mutations

Gene Mutations: Point Mutations A point mutation is a change in a single nucleotide. There are three types of point mutations:

Point Mutations: Substitutions In a substitution, one base is changed to a different base.

Point Mutations: Insertions and Deletions Insertion mutation: when a single extra base is added into the code Deletion mutation: when a single base is removed from the code

Point Mutations vs. Frameshift Mutations The substitution example was a point mutation. These last two examples of deletion and insertion were frameshift mutations. What’s the difference between a point mutation and frameshift mutation? Which has the most significant impact on the protein? Why?

Synonymous (“Silent”) Point Mutations What do you think a synonymous (“silent”) point mutation is? –Do not cause a change in the amino acid sequence –Generally, do not cause a change in the protein— however, can reduce the amount of a specific protein the cell makes or cause the structure of the protein to be changed in a manner that disrupts its functioning in the body Example: –TAT changed to TAC—both still code from Tyrosine –CTC changed to CTA—both still code for Leucine

Chromosomal Mutations  Deletion  Duplication  Inversion  Translocation

Chromosomal Mutations What changed? How would this type of change affect the protein?

Chromosomal Mutations What changed? How would this type of change affect the protein?

Chromosomal Mutations What changed? How would this type of change affect the protein?

Non-Disjunction Ex: Trisomy 21 or Down Syndrome Sometimes, there is an error in meiosis when egg or sperm cells divide resulting in too many or too few chromosomes. How do you think this type of change would impact an organism?

Mutation Impact The impact of a mutation on an individual also depends on where and when it occurs. If there was a mutation in the DNA of a zygote, how would that impact the individual? How might a mutation in a skin cell affect an individual?

Effects of Mutations Mutations can harm, help, or have no effect on an organism. Some mutations arise from mutagens—chemical or physical agents in the environment.

Effects of Mutations: Harmful Some of the most harmful mutations are those that dramatically change protein structure or gene activity. Normal red blood cell Sickle cell Example: Sickle cell disease affects the shape of red blood cells.

Effects of Mutations: Beneficial Mutations often produce proteins with new or altered functions that can be useful to organisms in different or changing environments. Example: The fruit of the Tahiti lime is seedless, a result of polyploidy.

Student Worksheet Answers