Gene Mutations A change in the DNA of a gene is called a mutation. Mutations in gametes can be passed on to offspring of the affected individual, but mutations in body cells affect only the individual in which they occur.

Types of Gene Mutations: 1. substitution – one base replaces another 2. insertion – one or more extra bases are added 3. deletion – one or more bases are deleted

Gene Mutations Base Insertion

Insertions and deletions are called frameshift mutations because they shift the “reading frame” of the genetic content. For example: The fat cat ate the hat. Insertion: The afa tca tat eth eha t. The fat cat ate the hat. Deletion: The fat ata tet heh at.

Effects of Mutations Most mutations have little or no effect, for example, a substitution may affect only a single amino acid and usually has no effect at all. Insertions and deletions which are frameshift mutations can change every amino acid that follows the point of mutation and therefore can have dramatic effects on the organism.

Some mutations produce beneficial variations that allow an organism to better adapt to its environment. Genetic material can be altered by: 1. natural or artificial events 2. environmental conditions 3. errors in replication 4. mutagens – chemical or physical agents in the environment that cause mutations

Are mutations always harmful? No! Some can be beneficial, or have no effect at all. Mutations that are harmful result in the production of different proteins. Mutations in gamete cells are passed on to offspring, therefore, they are more significant than a mutation that occurs in a body cell.

Write the names of the amino acids that correspond to each mRNA sequence below. mRNA sequence: AAU-UGG _____________ mutation sequence: AAA-UGG _____________ Which type of mutation occurred? _______________ Will the mutation affect the organism? Asp -Try Lys -Try Substitution YES

Write the names of the amino acids that correspond to each mRNA sequence below. mRNA sequence: UGU-CCG _____________ mutation sequence: UGU-CCC _____________ Which type of mutation occurred? _______________ Will the mutation affect the organism? Cys -Pro Cys -Pro Substitution NO

Write the names of the amino acids that correspond to each mRNA sequence below. mRNA sequence: GUU-UUG _____________ mutation sequence: GUU-GUU-G ___________ Which type of mutation occurred? _______________ Will the mutation affect the organism? Val -Leu Val -Val Insertion YES

Write the names of the amino acids that correspond to each mRNA sequence below. mRNA sequence: GGC-UCC _____________ mutation sequence: GGC- _____________ Which type of mutation occurred? _______________ Will the mutation affect the organism? Gly -Ser Gly Deletion YES