Chapter 3 Basic principles of Hereditary Chapter 5 Extensions of Mendel s Principles Chapter 6 Pedigree Analysis Application and genetic testing Chapter 25 Population Genetics Chapters 6b 9 11a The Structure of Chromosomes Chapter 22 Developmental Genetics and Immunogenetics Chapter 24 Quantitative Genetics Heterozygous cross 1 2 1 genotypic ratio 3 1 Phenotypic Ratio Genotype the set of genes possessed by an individual organism Phenotype appearance or manifestation of a characteristic in an organism Gene genetic factor that helps determine a trait DNA sequence that is transcribed into an RNA molecule Allele one of two or more alternate forms of a gene Locus position on a chromosome where a specific gene is located Heterozygote an individual organism that possesses two different alleles at a single locus Homozygote an individual organism that possesses two identical alleles at a single locus Dominance an allele of phenotype that is expressed in heterozygotes and homozygotes of the allele the only allele expressed in heterozygotes Mendel s Laws First Law of Segregation of alleles Each individual has two alleles coding for a trait The two alleles separate when gametes are formed Alleles separate in equal proportions Second Law of Independent Assortment Genes encoding different characteristics segregate independently of each other when gametes are formed EXCEPTION Sex linked characteristics Dihybrid Cross crossing of two traits of two individuals Multiple Gene Crosses Small punnett squares for each trait Multiply probabilities Chi Squared test Meiosis Crossing over occurs in prophase I Crossing over is between homologous chromosomes Stages of Meiosis 1 Prophase I 2 Metaphase I 3 Anaphase I 4 Telophase I 5 Prophase II 6 Metaphase II 7 Anaphase II 8 Telophase II Sex Determination and Sex Linked Characteristics Signs of being sex linked Results in reciprocal crosses not the same Different phenotypic ratios in the two sexes Sex Determination in Drosophila Even though they have X and Y chromosomes Their sex determination system is based on ratio of autosomes to X chromosomes o Females have a 1 0 X A ratio o Males have a 0 5 X A ratio o Metafemales have a 1 0 X A ratio o Metamales have a 0 5 X A ratio o Intersex flies have a 0 5 1 0 X A ratio Sex Chromosomes Haploid Sets of Autosomes X A Ratio Sexual Phenotype XX XY XO XXY XXX XXXY XX XO XXXX AA AA AA AA AA AA AAA AAA AAA 1 0 0 5 0 5 1 0 1 5 1 5 0 67 0 33 1 3 Female Male Male Female Metafemale Metafemale Intersex Metamale Metafemale In mammals sex determination XY SRY gene necessary and sufficient to produce males X inactivation Why did X inactivation evolve and provide an example of a phenotype associated with X inactivation Sex Determination in Other Species ESSAY Hymenoptera Haploid diploid system results in sex specific splicing of Hem Slipper limpets position in the stack of limpets determines the sex of the limpet Bluehead Wrasse can begin life male or femal but females can change into males Temperature dependent Turtles and alligators hav temperature of eggs determine Polygenic inheritance multiple sex determination systems occurring at once later in life the sex of offspring tilapia have XY and WZ Incomplete dominance phenotype of the heterozygote is intermediated between to two phenotypes of the two homozygotes flower coloring Codominance The phenotype of the heterozygote includes the phenotype of both homozygotes blood type Temperature sensitivity certain gene products may only function at an optimal temperature causing expression to be different at different temperatures Penetrance not all individuals with the genotype will express the trait Maternal effects the genotype of the mother influences phenotypes of the offspring Sex influenced traits expression of the phenotype is different based on what sex is being expressed in ABO Blood types Compound H No compound H makes you O Sugars Present o A galactosamine o B Glucosamine o O none Genotypes AO AB AA BB BO OO Antigens indicative of genotype Antibodies opposite to genotype Lethal genes homozygote is lethal in utero so you never observe those offspring alters ratios that are observed dominant or recessive Epistasis expression of one gene is dependent on the expression of another Complementation test crossing two mutants that have mutation at the same locus you expect mutation in offspring too If you cross two mutants and they have mutations at different loci than you expect some normal offspring Pedigree Analysis Pre natal Testing Aneuploidies of autosomal chromosomes in humans often produce offspring that don t survive aneuploidies in sex chromosomes can survive Hardy Weinberg Equation p 2 2pq q 2 1 Chi squared test to determine whether a population is in hardy weinberg equilibrium 1 Find Allele frequencies 2 Determine genotypic ratios 3 Perform chi squared test Causes of deviations from hardy weinberg Inbreeding no change in allele frequency o Loss of heterozygosity over time o Heterozygote crossing leads to more homozygotes over time The 4 forces changes in allele frequency o Random genetic drift random fluctuations in allele frequency due to sampling small numbers of gametes each generation genetic drift causes allelic frequencies in populations to diverge and often become fixed for one allele or the other o Mutation change allele frequency slowly millions of generations to cause a substitution ultimate force in evolutionary change o Migration only very high levels of migration from a population with a very different allele frequency will be detected as a deviation from hardy weinberg expectations q m qI qII o Selection many ways for natural selection to act Against ressesive alleles Against dominant alleles Against incompletely dominant allele Overdominance Underdominance Genetically effective population size individuals that contribute to the next generation Genetic drift equation s2 p pq 2N The structure of chromosomes Organisms may not be more complex based on number of chromosomes CoT Curves Chromosome packing in eukaryotes H1 H2A H2B H3 and H4 histone proteins Nucleosomes Chromatosome Soleniod Scaffolding proteins Chromosome packing in prokaryotes Tightly wound circular DNA Centromeres Telomeres Telomerase Chromosome mutations Deletion Duplication Inversion Pericentric inversion Paracentric inversion Translocation Mutation affect on metaphase lining up Developmental Consequences of chromosome mutations Translocation Consequences Autopolyploid Allopolyploid Polyploid