ZOL 341 1st edition Final Exam Study Guide Lecture 20 mutation an inherited change in DNA can occur in somatic can occur in germ line cells rare and occur at random mutation frequency in haploids the number of times mutation alters a particular gene in diploids the number of mutational events in a given gene over a defined period of time most often per DNA replication cycle hotspot of mutation a gene that has a higher mutation frequency than others in a given genome point mutations localized mutations that occur at a specific identifiable position on a gene base pair substitution the replacement of one nucleotide base pair by another transition one purine replaces another or one pyrimidine replaces another transversion a pyrimidine is replaced by a purine or vice versa effects of substitution silent does not alter the resulting amino acid sequence missense results in an amino acid change in the protein nonsense creates a stop codon in place of a codon specifying an amino acid Lecture 21 Nucleotide excision and replacement the undamaged strand serves as a template to guide incorporation of the correct complementary nucleotide UV repair a short segment of DNA surrounding the photoproduct is excised new DNA is synthesized to replace the removed nucleotides DNA recombination repair DNA replication can skip the lesions by bypassing the damages sections leaving single stranded gaps recombination repair directs recombination of the incomplete segment with the complementary strand using the sister chromatid as the repair template ploidy euploid a number of chromosomes that is an exact multiple of the haploid number eg 2n 3n aneuploid an uneven number of chromosomes eg 2n 1 2n 1 nondisjunction the failure of homologous chromosomes or sister chromatids to separate mosaicism being composed of cells of two genetically different types Lecture 22 polyploidy autopolyploidy duplication of chromosome sets within a species allopolyploidy combination of the chromosome sets of different species polyploidy is associated with an increase in cell size increased genome size increased nucleus volume increased cell volume chromosome alteration chromosome inversion reattachment in the wrong orientation chromosome translocation reattachment to a nonhomologous chromosome chromosome translocation translocation heterozygotes with one normal copy and one translocated copy of each chromosome may be in normal phenotype if no genes are disrupted by the breakage and reattachment events transposable genetic elements DNA sequences that can move within the genome transposition is enzyme driven insertional inactivation mutation caused by TE inserting itself into a gene Lecture 23 lac operon structure regulatory protein contains promoter that binds RNA polymerase operator binds lac repressor protein CAP cAMP region structural genes lacZ encodes beta galactosidase lacY encodes permease lacA endodes transacetylase all three are transcribed as a single polycistronic mRNA lacI encodes lac repressor protein is constitutively expressed lac operon function no lactose or presence of glucose lac operon is transcriptionally silent glucose is preferred no beta galactose is produced no allolactose in the cell lac repressor protein binds to lacO prevents transcription inducer allolactose Lecture 24 stem loop structures made of mRNA 3 4 stem loop termination stem loop halts RNA polymerase progression along the DNA within the leader region 2 3 stem loop antitermination stem loop prevents region 3 from interacting with region 4 allows RNA polymerase to continue through the leader sequence and into the structural genes gene regulation is necessary to ensure expression on genes in an accurate pattern during the various developmental stages of the life cycle differences among distinct cell types cis acting regulatory sequences bind trans acting regulatory proteins to control eukaryotic transcription activator proteins bind regulatory sequences to stimulate transcription repressor proteins bind other sequences to hinder transcription core promoter region binds RNA polymerase II and its associated transcription factors immediately upstream to the start of transcription proximal elements bind regulatory proteins general TFs to aid in promoter recognition Lecture 25 mutagenesis an organism is treated with a mutagen to create mutations randomly throughout the genome recombinant DNA a set of techniques for amplifying maintaining and manipulating DNA sequence in vitro and in vivo linear DNA the number of fragments number of restriction sites 1 vector carrier fragment of DNA isolated DNA fragments are inserted into a vector introduced into a biological system that amplifies the DNA the identical copies that result are called DNA clones plasmids some contain multiple cloning sites with unique restriction sites into which DNA can be cloned in some the MCS is in the lacZ gene so that an insert prevents expression of lacZ bacteriophages lambda up to 23 kb of DNA cosmid up to 45 kb of DNA yeast artificial chromosomes 200kb 2Mb of DNA Lecture 26 transgenes expression vectors contain the sequences needed for proper expression of the transgenes transgene must not contain introns eukaryotic expression vectors used in yeast or in tissue culture site directed mutagenesis nucleotide changes can be made in a DNA sequence desired change in the middle of primer primer used in PCR nonmutant plasmids selectively degraded shuttle vector can replicate in bacteria or in yeast manipulations in bacteria expression in yeast circular vector single cross over event integrates entire plasmid double crossover integrates only a segment linear vector single crossover results in deletion often used to introduce loss of function alleles Lecture 27 normal distribution approximation of the distribution of measurements of many biological characteristics variance a measure of the spread of distribution about the mean genetic variance the proportion of phenotypic variance due to genotypic differences environmental variance the portion of phenotypic variance due to variability in environment inhabited by individuals in a population partitioning genetic variance additive variance the added effects of all alleles contributing to the trait dominance variance dominance relationships interactive variance epistatic interactions heritability a measure of the proportion of phenotypic variation that is due to genetic variation values range from 0 1 near 1 indicates that genetic variation