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Three-factor cross: a cross whose partners differ at three different positions on a single chromosome typically used to map the relative locations of the genes. Gametes produced by a single meiosis and then analyzing their genotypes. Tetrad analysis: using a micromanipulator to separate the four spores or Hypothetical, genes to a single phenotype. Quantitative genetics: Analysis of the contributions of multiple, often

The two chromosomes must contort to pair the inverted part with its Inversion-heterozygote: A situation where one of a pair of homologousĬhromosomes has an inversion that reverses the order of genes in one segment. Version of a gene provides sufficient gene activity to give a normal Haplosufficiency: a condition where having one functional and one nonfunctional Usually these DNA sequences differ by only about Homologous chromosomes: chromosomes carrying different versions of the Inferences about inheritance and gene function. Genetic analysis: using the phenotypic outcomes of genetic crosses to make The term finished with a few lectures on the basic theories of population and quantitative genetics as established in the mid-20th century.Įpigenetic: heritable differences due to reversible modification of DNA ratherĮpistasis: change in phenotype caused when different alleles of one gene alterĮxome: the expressed part of the genome, all the exon sequences. Some instructors supplemented these topics with a smattering of molecular genetics, but serious treatment was left to a later course using the second half of the textbook. Analysis of genetic crosses then gradually revealed all the standard concepts-linkage and crossing over, gene mapping, sex linkage, epistasis, chromosome changes.

Next came the evidence that genes are on chromosomes, followed by the light-microscopy view of chromosome behaviour in meiosis. It began with Mendel's experiments and the principles they revealed-phenotypes are determined by genes whose alleles pass unchanged through the generations alleles are dominant or recessive pairs of alleles separate into gametes and form new combinations in each new generation. Our old course followed the canonical textbook structure, using genetic analysis (see Box 1 for Glossary) to teach the principles of transmission genetics, with the history of genetics providing the organizing framework (see, for example,, ).