ZOL 341 1st Edition Exam 2 Study Guide Lectures 11 19 Lecture 11 dosage compensation a mechanism that compensates for the difference in number of copies of genes between males and females central conclusions from molecular studies of Mendel s traits 1 Inheritance of alleles precisely parallels the pattern of transmission of morphological variants 2 Morphologic variation results from differences in structure and function of protein products of the alleles 3 Molecular analysis led to identification of DNA sequence differences between alleles and their consequences 4 Functional analysis of the protein products of each allele led to understanding of its function in producing the phenotype a wild type phenotype is produced when an organism has two copies of the wild type allele mutant alleles can be gain of function in which the gene product acquires a new function or express increased wild type activity loss of function in which there is a significant decrease or complete loss of functional gene product codominance dominance relationships of ABO alleles IA completely dominant to i IB completely dominant to i IA and IB codominant to each other Lecture 12 pleiotropy the alteration of multiple distinct traits by a mutation in a single gene gene interaction the collaboration of multiple genes in the production of a single phenotypic characteristic genetic dissection used to investigate gene action completion of one step generates the substrate for the next step in the pathway completion of every step is necessary to produce the end product epistasis the alleles of one gene modify or prevent expression of alleles of another gene mutation of one gene in a pathway may prevent the production of the end product a minimum of two genes are required these usually participate in the same pathway no interaction 9 3 3 1 ratio dominant suppression a dominant allele at one locus suppresses expression of a second locus genetic heterogeneity mutations in different genes can produce the same or very similar mutant phenotypes genetic complementation when mating of two organisms with similar mutant phenotypes leads to wild type offspring complementation occurs when the mutations in the parents affects Lecture 13 CLASS WAS CANCELLED PROFESSOR WAS ILL SLIDES FOR VIEWING ARE ON D2L homework and quiz are still posted on d2l as usual Lecture 14 recombination percent recombination map units mu cM not the same phenotype as either of the parents percent recombination total recombinants total pyrogeny linkage linkage produces 8 different gamete genotypes with unequal frequencies parental types will be observed most frequently the 6 recombinant gamete classes are produced at frequencies significantly lower than predicted by chance within each crossover class ie single double both gamete types that result have equal frequency double crossover classes are the least frequent because both crossover events must occur to produce these memorize the above rules for three point test cross analysis because they will be important for figuring out the problems three point mapping ask these five questions to help solve problems are the data consistent with the proposal of genetic linkage Ie does the data support the rules stated above what are the alleles on the parental chromosome there will be 3 sets of alleles what is the gene order on the chromosome what order are these alleles in what are the recombinant frequencies of the gene pairs use equation above to calculate recombinant frequency is the frequency of the double crossovers consistent with independence of the single crossovers is the frequency significantly lower than for the single crossovers Lecture 15 linkage doing a three point test cross determine nonrecombinant and DCO offspring classes figure out gene order determine SCO classes calculate RF values calculate expected DCO calculate COC and interference values haplotype the specific array of alleles in a set of linked genes on a single chromosome haplotypes may consist of any combination of linked genes with genetic variation linkage equilibrium B over generations crossing over among original haplotypes will produce new combinations by chance the genotype for a chromosome at one gene is thus expected to be independent of its genotype for other genes this is called linkage equilibrium when certain haplotypes are maintained in a population usually due to natural selection it is called linkage disequilibrium Lecture 16 bacterial transfer conjugation donor to recipient transformation donor to the environment to recipient transduction donor to viral vector to recipient 1 way only events must have crossover between recipient DNA and donor DNA plasmid types F fertility plasmid contains genes that promote its own transfer from donors to recipients R resistance plasmid carries antibiotic resistance genes that can be transferred to recipient cells bacteria prototrophic bacteria can synthesize everything that they need to grow and reproduce autotrophic bacteria contain a nutritional mutation that results in an inability to synthesize an essential biological molecule Lecture 17 F the result of imperfect excision of the F factor from an Hfr chromosome contains a functional F factor plus a segment of the bacterial chromosome F factor mating exconjugants that contain a complete F factor are called partial diploids aka merodiploid because they contain two copies of the bacterial chromosome genes found on the F factor partial diploidy retained as a characteristic of the exconjugants and their descendants can be used to examine the mode of action of bacterial genes and their regulation cotrans frequency lowest cotrans frequency flanking genes further apart highest cotrans frequency closest pair transduction the transfer of genetic material from a donor to a recipient cell by way of a bacteriophage bacteriophage infects a donor cell and some progeny phages accidently incorporate a fragment of donor DNA rather than a copy of the phage chromosome these progeny phage then infect a recipient cell and inject the donor DNA generalized transduction phages package a random piece of bacterial DNA into progeny phage heads Lecture 18 gel electrophoresis smaller molecules migrate more rapidly than larger molecules SNP single nucleotide polymorphisms restriction endonuclease enzymes that cut DNA at specific sequences restriction sites are usually palindromes each strand of the ds restriction sequence has the same nucleotide order RFLPs