GCD 3022 1st Edition Lecture 26Outline of Last Lecture I. Epigeneticsa. Epigenetics vs. classical geneticsb. Epigenetic gene regulationc. Targeted genesd. Igf2 geneII. Splicing Regulationa. SR proteinsb. Advantage of alternative splicingc. Splicing repressor Example 1d. Splicing repressor Example 2e. Types of exonsIII. mRNA half lifea. Definitionb. AU-rich elementsIV. RNA interferencea. Mechanism b. Non-coding RNAc. miRNA hybridizationThese 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 interferenceOutline of Current LectureI. Mutationsa. Allelic variationb. Types of mutations i. Chromosome mutationsii. Genome mutationsiii. Gene mutationsc. Types of cellsi. Germ-lineii. Somatic II. Mutations that change DNA sequencea. Point mutationsi. Base substitutionii. Transitioniii. Transversioniv. Addition or deletionIII. Mutations that alter the coding sequencea. Silent mutationsb. Missense mutationsc. Nonsense mutationsd. Frameshift mutationsIV. Mutations outside of the coding sequencea. Up mutationsb. Down mutationsV. Effects on genotype and phenotypea. Mutations that affect wild-type phenotypei. Forward and reverse mutationsii. Deleterious and lethal mutationsiii. Beneficial mutationsiv. Conditional mutationsb. Suppressor mutations i. Two typesVI. Chromosome mutationsa. Chromosomal breakpointb. Position effectCurrent LectureI. Mutations: a heritable change in the genetic materiala. 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 structureii. Genome mutations: changes in the chromosome numberiii. Gene mutations: relatively small change in DNA structure that affects a single gene. c. Types of cellsi. 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 sequencea. 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 (nota point mutation).III. Mutations that alter the coding sequencea. 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 expressionb. Down mutations: decrease expressionV. Effects on genotype and phenotype: often involve the wild-type phenotype.a. Mutations that affect wild-type phenotypei. 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