12-4 and 5 Mutations and Gene Regulation I. Kinds of Mutations in Genes A. Point Mutations – mistakes that occur at a single point in a genes DNA sequence 1. Substitution - where one Nitrogenous Base is substituted for another 2. Insertion- where a Base is included but does not belong 3. Deletion- where a Base is left out B. Frameshift mutations - when an insertion or deletion occurs it causes a shift in the DNA’s codons. Frameshifts can alter proteins so much that they no longer function. C. Chromosomal Mutations- A change in the number or structure of chromosomes 1. Deletion- A section of a chromosome is missing 2. Duplication- A section of a chromosome is repeated twice 3. Inversion- section of a chromosome is flipped or appears in reverse 4. Translocation- A section of a chromosome gets misplaced in another chromosome D.Both types of mutations can cause dramatic changes in proteins and activities. Some may cause problems others may be beneficial. Mutations cause diversity. E. Polyploidy - A plant with an extra set of chromosomes. In plants this is often beneficial. II. Gene Regulation- How a Gene is expressed in the cell A. Operon- In Prokaryotes, a gene has a repressor that blocks the transcription process B. Promotor Sequence- In Eukaryotes a promoter sequence and TATA box positions the RNA polymerases for transcription C. Regulation of Gene Expression – A series of genes known as hox genes control development and differentiation.