A permanent change that occurs in a cell’s DNA is called a mutation. Molecular Genetics Mutations A permanent change that occurs in a cell’s DNA is called a mutation. Types of mutations Point mutation Insertion Deletion

Can occur spontaneously Molecular Genetics Causes of Mutation Can occur spontaneously Chemicals and radiation also can damage DNA. High-energy forms of radiation, such as X rays and gamma rays, are highly mutagenic.

Molecular Genetics Hox Genes Hox genes are responsible for the general body pattern of most animals.

Body-cell v. Sex-cell Mutation Molecular Genetics Body-cell v. Sex-cell Mutation Somatic cell mutations are not passed on to the next generation. Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring.

Point Mutation A Point Mutation is caused when a single base is changed in the DNA strand. 3 types: Nonsense: Change causes a Stop codon, shortening the protein Missense: Changes to a different amino acid, may cause loss of function Silent: Base changes codon to the same Amino Acid, so not seen.

Missense A substitution Mutation THE BIZ FAT CAT ATE THE WET RAT Results: Changes a single Amino acid Disease: Achondroplasia (Dwarfism)

NONSENSE Substitution THE BIG RAT The substitution prematurely stopped the code. DISEASE: Muscular Dystrophy

Frameshift Mutation (Insertions and Deletions) Caused by adding or a deleting a base which throws off the 3 base coding frame. Example: Dowling–Degos Disease - over pigmentation - Looks like big freckles

DELETION Removal of a single base THB IGF ATC ATA TET HEW ETR AT Called a frameshift mutation. Throws off the 3 base reading frame causing a new amino acid sequence that makes the incorrect protein DISEASE: Cystic fibrosis

INSERTION Frameshift mutation: Adding a base – Throwing off the reading frame THE BIG ZFA TCA TAT ETH EWE TRA T DISEASE: CROHN’s DISEASE

DUPLICATION Extra copy/repeat of a segment of DNA. THE BIG CAT BIG CAT ATE THE WET RAT Disease: Charcot-Marie-Tooth Disease

EXPANDING MUTATION (Tandem Repeats) A duplication that keeps occurring. Lengthening the protein until almost unuseable THE BIG BIG FAT CAT THE BIG BIG BIG FAT CAT THE BIG BIG BIG BIG FAT CAT DISEASE: Hunnington’s Disease

Real Mutations Visible mutations usually required more than one genetic mutation.

Down Syndrome: Trisomy 21 Nondisjunction event causing the 21st chromosome pair to not separate during meiosis (Gamete formation)

Multi X female (Nondisjunction during egg formation – X chromosomes fail to separate)

Muscle protein gene mutation Muscle protein gene mutation. Causes double the muscle tissue to form resulting in one buff dog… or super strong German Toddler

Extra Limbs

Color Change Mutations

Extra Fingers - Polydactyly

Molecular Genetics