Section 13.3/4: “Mutations & Gene Expression” Text Pages 372-376

What Are Mutations? Change in the genetic material of a cell May occur in somatic cells (aren’t passed to offspring) May occur in gametes (eggs & sperm) and be passed to offspring

Gene Mutations=produce changes in a single gene Types of Mutations Gene Mutations=produce changes in a single gene Chromosomal Mutations=produce changes in whole chromosomes

Gene Mutations Point Mutations=involve changes in one or a few nucleotides Substitutions Insertions Deletions (Generally occur during replication) Frameshift Mutations=shifts the “reading frame” of a genetic message by inserting/deleting nucleotides

Substitution One base is changed to a different base. Usually affects no more than a single amino acid. Example: one codon of mRNA changed from CCC (proline) changed to ACC (threonine)

Insertions/Deletions One base is inserted or removed—shifts the “reading frame” Affects every amino acid following the mutation, altering the protein

Example—Gene Mutations Sickle Cell disease is the result of one nucleotide substitution Occurs in the hemoglobin gene

Example--Frameshift Mutation Original: The fat cat ate the wee rat. Frame Shift (“a” added): The fat caa tat eth ewe era t.

Amino Acid Sequence Changed (Deletion)

Gene Mutation Animation

Chromosome Mutations May Involve: Changing the structure of a chromosome The loss or gain of part of a chromosome Types: Deletion, Duplication, Inversion, Translocation

Deletion Loss of part of a chromosome

Duplication Produces extra copy of all or part of a chromosome

Inversion Reverses the direction of part of a chromosome

Translocation Part of one chromosome breaks off and attaches to another.

Chromosome Mutation Animation

Are Mutations Helpful or Harmful? Mutations happen regularly Effects vary widely have little or no effect (neutral) produce beneficial variations (evolution) negatively disrupt gene function (alter protein structure) Chemicals & UV radiation cause mutations (mutagens) Many mutations are repaired by enzymes

13.4: Gene Expression Gene regulation helps cells undergo differentiation or specialized in structure and function. Example—As an embryo develops, different sets of genes are regulated, allowing them to become specialized “Homeotic Genes”=Master control genes Regulates organs that develop in specific parts of the body.