Chapter 10 Mutations Student 2015

10.16 Mutations can change the meaning of genes  A mutation is any change in the nucleotide sequence of DNA.  Mutations can involve large chromosomal regions or just a single nucleotide pair. © 2012 Pearson Education, Inc.

10.16 Mutations can change the meaning of genes  Mutations within a gene can be divided into two general categories. 1.Base substitutions involve the replacement of one nucleotide with another. Base substitutions may – silent mutation, – change the amino acid coding, producing a missense mutation – lead to a base substitution that produces an improved protein that enhances the success of the mutant organism and its descendant, or – nonsense mutation, stop codon © 2012 Pearson Education, Inc.

10.16 Mutations can change the meaning of genes 2.Mutations can result in deletions or insertions that may – alter the reading frame (triplet grouping) of the mRNA, so that nucleotides are grouped into different codons, – produce a nonfunctional polypeptide. © 2012 Pearson Education, Inc.

Figure 10.16B Normal gene Nucleotide substitution Nucleotide deletion Nucleotide insertion Inserted Deleted mRNA Protein Met Lys Phe Lys Phe Ala Gly Ser AUGAAGUUU GGC G CA GC G CA A G UUU AUGAA Met Lys Ala His Leu GUU AUGAA GGC G CA U U Met Lys Ala His Leu GUU AUGAA G G C UG G C

10.16 Mutations can change the meaning of genes  Mutagenesis is the production of mutations.  Mutations can be caused by spontaneous errors that occur during DNA replication mutagens, which include – high-energy radiation such as X-rays and ultraviolet light and – chemicals. © 2012 Pearson Education, Inc.

Are mutations always harmful? Dark winged tiger swallows result from a mutation Papilio glaucus Battus philenor (Poisonous)

Are mutations always harmful? Pesticide resistance in mosquitos. – Harmful or helpful? Antibiotic resistance in bacteria. – Harmful or helpful? Polyploidy – Extra sets of chromosomes