Mutations 13.3

Mutations Mutation: Any change in the DNA sequence Can be harmful, helpful, or neither. 2 types: Gene mutations and chromosomal mutations Point mutation: occurs in a single point in the DNA sequence Generally occur during replication Three types: substitution, insertion, and deletion.

Point mutations http://www. life. illinois Substitution One single base is switched Usually affects only one amino acid Sickle cell disease in humans Insertion and deletion One base is either inserted or removed Dramatic changes affecting many amino acids Also called framshift mutations May have major effects on protiens

Chromosomal Mutation: Changes in chromosome number or structure 1) INVERSION: the order of genes on a chromosome is inverted (reversed) 2) TRANSLOCATION: the movement of a chromosome fragment to a nonhomologus chromosome

3. DELETION Loss of a all or part of a chromosome 4. DUPLICATION Duplication of all or part of a chromosome

Causes and Effects of Mutations

Causes of mutations Errors in replication 1 in 10 million bases is copied incorrectly This accumulates over time Mutagens (chemical or physical agents in the environment that cause mutations) Pesticides, tobacco smoke, environmental pollutants EM radiation, X-rays, UV light

Effects of mutations Cells can sometimes repair damages from mutagens If not, several possible outcomes: Base-pairing can be disrupted DNA strands weaken, which can increase the chances of chromosomal mutations.

Helpful or harmful? Some mutations have no effect on the organism. Some are harmful Some are helpful HUGE variation!

Harmful mutations Mutations that dramatically alter the protein structure and gene activity are harmful. Cancer Sickle-cell disorder Other disorders (more on that later)

Beneficial Mutations? May alter an organism to make it more fit for its environment Insects resisting pesticides Bacteria mutating to resist antibiotics Human mutations Increased bone strength Viral resistance, such as HIV Polyploidy Larger fruits and veggies