Genetic Mutations

Genetic Changes What is a mutation? A mistake or change in the genetic (DNA) make-up of an organism Can occur during replication, transcription or translation! There are several different types of mutations Point mutations (substitutions) Frameshift mutations (insertions or deletions) Chromosomal mutations (involving more than one base pair) Spontaneous mutations (happen randomly) Mutation Story

Point & Frameshift Mutations Point mutation (substitution) Change in a single base pair in DNA THEDOGBITTHECAT Change the ending “T” to a “R” THEDOGBITTHECAR Missense mutation: the mutation changes the amino acid Silent mutation: the mutation does NOT change the amino acid Nonsense mutation: the mutation changes the amino acid to a “STOP”

Nonsense vs. Missense Mutations The new codon causes an incorrect amino acid to be inserted into the protein. The effects on the function of the protein depend on what is inserted in place of the normal amino acid. NONSENSE The new codon causes the protein to prematurely terminate, producing a product that is shortened and often does not function.

Deletion / Insertion A shift in one place (frameshift mutation) HAVEANICEDAY - Delete the “N” and shift everything down HAVEAICEDAY - Add another “N” and shift everything up HAVEANNICEDAY

Chromosomal Mutation Trisomy Chromosomes are physically changed May break and rejoin incorrectly May not separate correctly (or at all) during Meiosis  NONDISJUNCTION Trisomy Example of a chromosomal mutation in which a zygote ends up with an extra chromosome (Down Syndrome

Types of chromosomal mutations: Deletion of all or part of a chromosome. Duplication repeats a segment of a chromosome. Inversion is when part of a chromosome becomes oriented in the reverse of its usual direction. Translocation is when part of one chromosome breaks off and attaches to another, non-homologous chromosome.

Duplication Repeats a segment of a chromosome

Inversion part of a chromosome gets reversed

Translocation part of one chromosome breaks off and attaches to another, non-homologous chromosome

Inheritance of Mutations Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring. Somatic cell mutations are NOT passed on to the next generation

Spontaneous Mutations Occur randomly Some environmental agents causes Prolonged exposure to X-rays Prolonged/excessive exposure to UV radiation Radiation exposure Certain chemicals