Types of mutations Mutations are changes in the

Types of mutations ◦ Mutations are changes in the genetic material ◦ There are two basic types of mutations: Gene mutations - mutations that produce changes in a single gene Chromosomal mutations that produce changes in whole chromosomes

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.

Gene mutations �Point mutations: �Involves changes in one or a few nucleotides (they occur at a single point in the DNA sequence) �They can be: � Substitutions � Insertions � Deletions

Substitutions One base is changed to another Substitutions usually only affect a single amino acid

Insertions and Deletions A base is either inserted or removed from the DNA sequence If a nucleotide is added or deleted, the bases are still read in groups of three, so every codon after is changed These types of mutations cause Frameshift mutations Can cause major changes to the protein, to the point where it can’t perform its normal function

Chromosomal mutations �Involve the chromosomal changes in the number or structure of chromosomes �Can change the locations of genes on chromosomes, and the number of copies of some genes �Four types: �Deletions �Duplications �Inversions �Translocations

Duplications and Deletion Duplication (Nondisjunction): ◦ The failure of a chromosome to separate from its homologue during meiosis ◦ One gamete receives an extra copy of a chromosome and the other lacks it Deletion: ◦ Loss of a piece of a chromosome

Translocations and Inversions Translocation: ◦ When a chromosome piece breaks off and reattaches to another, nonhomologous chromosome Inversion: ◦ Chromosome segment breaks off and then reattaches in reverse orientation to the same chromosome

Significance of Mutations Most mutations are neutral (they have little or no effect) Mutations that cause dramatic changes in protein structure or gene activity can be very harmful Mutations are a source of genetic variability in a species Polyploidy- a mutation where an organism has an extra set of chromosomes Polyploid plants are often larger and stronger

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

Down Syndrome: Trisomy 21 Nondisjunction event causing the 21 st 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. Causes double the muscle tissue to form resulting in one buff dog… or super strong German Toddler (results from either: Deletion or Missense)

Extra Limbs (Chromosal)

Color Change Mutations (Thought to be a point mutation)

Extra Fingers – Polydactyly (Chromosomal Mutation)

Molecular Genetics