Mutations Chapter 12

What is a mutation? Mutations are changes in the DNA or RNA sequence that affect genetic information. At the molecular level, mutations are usually caused by errors made during DNA Replication, Protein Synthesis, etc. However, sometimes environmental factors can cause mutations. It simply depends on the type of mutation.

Types of Mutations Gene Mutations result from changes in a single nucleotide. They are at the DNA / RNA level. ▫Point Mutations ▫Frameshift Mutations Chromosomal Mutations involve changes in parts of chromosomes. ▫Deletion ▫Duplication ▫Inversion ▫Translocation

Gene Mutations Point Mutations are mutations that are only affected at one nucleotide. Example: ▫ORIGINAL STRAND:  A T T G C C ▫MUTATED COMPLEMENT STRAND:  T A A C G C

Gene Mutations Frameshift Mutations involve the insertion or deletion of a nucleotide. This causes a change in the entire reading frame. Example: ▫ORIGNAL DNA STRAND:  A T T G C C ▫MUTATED mRNA COMPLEMENT STRAND:  U A A G G

Think of gene mutations, and its effects on a normal sentence. Original Sentence: ▫TIME TO DREAM Point Mutation: ▫TAME TO DREAM Frameshift Mutation / Deletion: ▫TETO DR EAM__ Frameshift Mutation / Insertion: ▫TIIM ET ODREAM

Chromosomal Mutations Deletion occurs when one or more genes is lost in a chromosome.

Chromosomal Mutations (cont) If a gene is inserted more than once on a chromosome, it is called duplication.

Chromosomal Mutations (cont) During inversion, part of a chromosome gets reversed from its original direction.

Chromosomal Mutations (cont) Translocation describes when one part of a chromosome breaks off and attaches to a homologous chromosome. ▫This is called crossing-over and occurs naturally during Meiosis!

Chromosomal Mutations (cont)

The good, the bad, and the ugly Most mutations are disadvantageous (harmful), but some mutations are advantageous (good). These good mutations allow species to adapt as environmental factors fluctuate. In other cases, mutations simply make a change that is neither good not bad.

Why are mutations important? Mutations facilitate biodiversity as well as evolution. ▫Biodiversity = variety of species on earth ▫Evolution = change over time If species do not adapt to changes in the environment, they will become extinct.