PCB 3063 General Genetics Lecture Notes Exam 2 This set of notes is 16 pages If you want to find notes for a specific date ex 1 27 or topic codominance press Ctrl F on your keyboard Command F for Mac users and type in what you want to find It ll search the document for whatever specific word phrase you typed in and save you the time of scrolling through everything Mon 2 10 Cytoplasmic inheritance extranuclear DNA passed on to offspring Extranuclear in mitochondria chloroplast Genome in mitochondria chloroplast dif than DNA in nucleus Mitochondria chloroplasts thought to be descended from symbiotic bacteria Variegated plant w 2 dif colors on leaves or branches Chloroplast green Parent cell has the 2 dif types Parent cell divides cytoplasm segregates Daughter cells have one or the other color Glucoplast white Ex 4 o clock plant White female x male all white Green female x male all green Variegated female x male all variegated Offspring color only depends on mother Maternal inheritance only mom s cytoplasmic info passed on Maternal mitochondrial info passed on to offspring Mitochondria get mutations over time Egg can take mostly mutated partly mutated or few mutated cells Maternal effect mutations nuclear genes expressed as alternate phenotype Come from mother s eggs Required for embryonic development Not influenced by offspring s own genome at all only mother s from egg not nucleus Mutation expressed when mom is homozygous recessive for trait aa If she is ALL offspring are affected all of her eggs are bad Linkage 2 traits correlated Independent assortment nuclear chromosomes loci split during cell division Segregation mitochondrial mitochondria splits linkage Ex Mendel s peas showed indep assortment not Mendelian inheritance 4 chromosomes with 7 traits 1 3 loci 2 2 loci 3 1 loci 4 1 loci Showed linkage Ex Punnet experiemnts Flower color pollen shape in garden pea In F2 expected 9 3 3 1 ratio got 15 1 1 3 Threw out hypothesis of Mendelian inheritance turns out it was actually linkage Ex Fruit fly Mutations in eye color wing shape and body color Originally thought it was X linked linkage Eye color red normal or purple mutant Wing shape normal or vestigial mutant Flies with red eyes tended to have vestigial wings Flies with purple eyes tended to have normal wings Not independent assortment but some kind of linkage Wildtype normal allele most common phenotype Ex normal red and mutant purple Red pr Purple pr Ex Normal red female x Vestigial purple male P v pr y sex chromosome 1 X sex chromosome 2 X or Y F1 all normal red v pr for female and y for male Mapping with 2 loci produces 4 dif types of offspring F2 4 dif types of offspring Genotype Phenotype of offspring v pr v pr normal purple normal red vestigial purple vestigial red 1339 1195 151 154 Largest s parental genotypes Smallest s new combinations recombinants Total 2800 Genetic distance of new genotypes in F2 Genetic distance recombinant1 recombinant2 total 100 Unit centimorgan or map unit mu 1 1 centimorgan 1 mu Shows when there is no pleiotrophy Recombinant new combinations of genes Paternal maternal chromosomes combine in new ways Happens during meiosis when tetrads crossover Results only revealed in F2 gen Physical distance distance b w genes on literal DNA strand measured in base pairs Not same as recombinant Tester individual used in test cross Bred to individual with unknown genotype Always male homozygous recessive no s Recombination happens in female not male Use male to measure recombination in female Cis configuration s line up with s Trans configuration s don t line up pr v v pr Mapping measure connection b w alleles Determine map units between two different genes Ex Flies Body color gray or black b Wing type normal or vestigial v P Gray vestigial x Black normal v x b v b Gender doesn t matter in P gen Don t use any Y s F1 All Gray normal v b trans testcross with Tester b v Male b v F2 4 dif offspring types Phenotype Gray vestigial Black normal Gray normal Black vestigial Total of offspring 42 42 8 8 100 parental parental recombinant recombinant recombinant 8 8 100 100 16 100 16 map units b w body color and wing type Ex Flies Normal vestigial wing type and wildtype cinnabar c eye color P Vestigial wildtype x Normal cinnabar v c v c F1 All normal wildtype v c trans testcross with F2 Mapping with 2 loci 4 dif offspring types Phenotype Vestigial wildtype Normal cinnabar Vestigial cinnabar Normal wildtype Total of offspring 90 90 10 10 200 parental parental recombinant recombinant Tester v c Male v c homozygous recessive recombinant 10 10 200 100 20 200 100 10 map units Linkage no independent assortment genes are all lined up on the same chromosome Wed 2 12 Genes arranged linearly on chromosome Have specific position location Each location can only have 1 gene any of the one gene s alleles are possible Crossover happens in location between 2 gene loci of interest If not recombination isn t noticeable Recombination always 50 50 independent assortment genes on separate chromosomes Or if it IS recombination it s indistinguishable from independent assortment 50 impossible parental genotype frequency recombinant genotype Ex Mapping Cinnabar eye linked to vestigial wing 10 map units apart Vestigial wing linked to black body 16 map units apart So cinnabar linked to black All 3 loci in linear order on same chromosome Find gene order Possibilities black 16 mu vestigial 10 mu cinnabar black cinnabar 26 black 6 mu cinnabar 10 mu vestigial black vestigial 16 Find distance between black cinnabar to determine which order is right P Black x Cinnabar b c b c If trait not mentioned assume it s normal F1 All trans b x Test cross c b c Male c b F2 2 loci mapped 4 dif offspring types Phenotype offspring Normal cinnabar 47 Black normal 47 3 Normal normal 3 Black cinnabar Total 100 parental parental recombinant recombinant recombinant 3 3 100 100 6 map units between black and cinnabar Correct order black 6 mu cinnabar 10 mu vestigial Recombination frequency for given loci depends on distance b w them Chromosome map physical distance b w loci shown Independent assortment 4 dif gametes test cross gives 1 1 1 1 ratio 2 genes with 2 alleles Linked no crossover 2 dif gametes 1 1 ratio only parental genotypes Complete linkage Same ratio as independent assortment Linked crossover 4 dif gametes parent recombinant ratio Greater loci distance increased recombinant proportion More likely to form recombinant closer to 50 More likely for space in between
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