GCD 3022 1st Edition Lecture 26 Outline of Last Lecture I Epigenetics a Epigenetics vs classical genetics b Epigenetic gene regulation c Targeted genes d Igf2 gene II Splicing Regulation a SR proteins b Advantage of alternative splicing c Splicing repressor Example 1 d Splicing repressor Example 2 e Types of exons III mRNA half life a Definition b AU rich elements IV RNA interference a Mechanism b Non coding RNA c miRNA hybridization These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute d RNAs in RNA interference Outline of Current Lecture I Mutations a Allelic variation b Types of mutations i Chromosome mutations ii Genome mutations iii Gene mutations c Types of cells i Germ line ii Somatic II Mutations that change DNA sequence a Point mutations i Base substitution ii Transition iii Transversion iv Addition or deletion III Mutations that alter the coding sequence a Silent mutations b Missense mutations c Nonsense mutations d Frameshift mutations IV Mutations outside of the coding sequence a Up mutations b Down mutations V Effects on genotype and phenotype a Mutations that affect wild type phenotype i Forward and reverse mutations ii Deleterious and lethal mutations iii Beneficial mutations iv Conditional mutations b Suppressor mutations i Two types VI Chromosome mutations a Chromosomal breakpoint b Position effect Current Lecture I Mutations a heritable change in the genetic material a Allelic variation caused by mutations Thus mutations can be positive because they are the basis for evolutionary change and are needed in order for a species to adapt to changes in the environment Mutations are more likely to be harmful than beneficial however b Types of mutations i Chromosome mutations changes to chromosome structure ii Genome mutations changes in the chromosome number iii Gene mutations relatively small change in DNA structure that affects a single gene c Types of cells i Germ line cells that give rise to gametes eggs and sperm Germ line mutations occur directly to a sperm or egg cell or in a gamete precursor ii Somatic all other non gamete cells Somatic mutations occur directly in a body cell or body precursor cell II Mutations that change DNA sequence a Point mutations change in a single base pair i Base substitution where one base is substituted for its complement ii Transition change of a pyrimidine to another pyrimidine C T or a purine to a purine A G iii Transversion change of a pyrimidine to a purine or vice versa iv Addition or deletion addition or deletion of a short sequence of DNA not a point mutation III Mutations that alter the coding sequence a Silent mutations base substitution that do not alter the amino acid sequence of the polypeptide due to degeneracy of the genetic code b Missense mutations leads to incorporation of the wrong amino acid If different polypeptide has the same function as the original the mutation is called neutral c Nonsense mutations introduces a stop codon into an mRNA sequence so that translation stops early d Frameshift mutations involve the addition or deletion of some nucleotides so that the reading frame is shifted and a new polypeptide is produced IV Mutations outside of the coding sequence change the level of gene expression a Up mutations increase expression b Down mutations decrease expression V Effects on genotype and phenotype often involve the wild type phenotype a Mutations that affect wild type phenotype i Forward and reverse mutations forward changes the wild type genotype into some new variation Reverse mutations change a mutant allele back to the wild type can also be called a reversion ii Deleterious and lethal mutations deletion of genetic material often results in a lethal mutation death of the individual iii Beneficial mutations enhance the chance of survival or reproduction of an individual The environment can determine whether a mutation is deleterious or beneficial iv Conditional mutations affect the phenotype of an individual under a defined set of conditions Example temperature sensitive mutation b Suppressor mutations when a second mutation counteracts the effects of a first mutation i Two types intragenic second mutant site is within the same gene as the first mutant site and intergenic second mutant site is in a different gene than the first VI Chromosome mutations change in chromosome structure that affects a gene a Chromosomal breakpoint site of breaking and rejoining in a chromosome Often the site of mutation b Position effect when a gene is left intact after a breakpoint mutation but its expression is altered due to its new location This new expression can be due to the gene s new position next to a regulatory sequence or movement to a heterochromatic region