A mutant is different than normal The mutant

A mutant is different than “normal”. The mutant characteristic is passed on to the next generation.

Central Dogma of Biology DNA -> RNA -> Protein DNA Transcription m. RNA Translation Protein Gene Function

Mutations Often Result in the Synthesis of Abnormal Proteins DNA -> RNA -> Protein X DNA Transcription X m. RNA Translation X Protein Abnormal Gene Function

Mutation of the Fly dpp gene

Mutation of the Fly dpp gene

Recessive versus Dominant Mutations/Alleles Allele: A particular variant of a gene (could be normal or mutant). Recessive mutations: Both copies of the gene must be mutated to manifest defect (homozygous). • Loss-of-function mutations are typically recessive. • Recessive mutations are represented by lower case letters. • + = wildtype, m = recessive mutation Dominant mutations: The defect is manifest when only copy of the gene is mutated (heterozygous). • Dominant mutations can confer new activities or interfere with normal gene function. • Dominant mutations are represented by upper case letters. • + = wildtype, M = dominant mutation

Genotype versus Phenotype Genotype: The genetic make-up of an individual. Examples: +/+, +/m, m/m, +/M Phenotype: The appearance of an individual. Example: Individuals having a +/+ or +/m genotype have a normal phenotype. Individuals having m/m genotype have mutant phenotype. Individuals with one normal (+) and one mutant (m) copy of a gene are called carriers for the mutation (+/m).

Abe Lincoln

One quarter of the offspring from two Marfan carrier parents will have Marfan Syndrome Two types of mother’s eggs mf + Two types of father’s sperm + +/++ mf +/mf mf + mf mf/+ + + mf/mf mf mf +/+ = 1/4 offspring = Normal +/mf or mf/+ = 1/2 offspring = Normal mf/mf = 1/4 offspring = Marfan

Putting Mutations Into Groups A. Two Genes Function in a Common Process

Putting Mutations Into Groups B. Two non-responding mutations in the same gene Mutant m 1 Mutant m*1 Signal lacking -> No response m 1 m*1 Signal lacking -> No response

Putting Mutations Into Groups C. Two non-responding mutations in different genes Mutant m 1 Mutant m 2 Signal lacking -> No response Receptor lacking -> No response m 1 Normal offspring + m 2 Signal and Receptor present -> Response

The Body Plan of a Fly Maggot D Tail Skin P A Head Thorax Nervous Syste (inside) Abdomen V “Denticle” Hairs

Fly Embryonic Patterning Mutants Anterior-Posterior Patterning Mutants Dorsal-Ventral Patterning Mutants