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Review Question Is it possible for a male cat to be a tortoiseshell? Sex Determination in Drosophila and other organisms X chromosome: Autosome Balance In Drosophila, sex is determined by the ratio of the number of X chromosomes to the number of sets of autosomes Genetic sex determination systems vary Other kinds of sex determination • • • • • • Grasshoppers, crickets, roaches: XO Nematodes: ______ Bees, ants, wasps: haplodiploidy Many Snakes: _______ Lizards: both XX/XY and ZZ/ZW systems Crocodiles, most turtles, and some lizards, sex is determined by the incubation temperature during a critical period of embryo development. This is known as ____________________________. Temperature Dependent Sex Determination In some animals, sex is not ‘determined’ at all! Some fish change sex as they get older or larger. In clown fish, largest group member is ______, second largest is _______, and all others are ______________. Sometimes the largest fish in the group will become ______, all others will be ______ (wrasses). Coral Goby Gobiodon histrio Monogamous pairs If mate dies or leaves, resident will____________ _______________ _______________. And some species are all female Cnemidophorus uniparens are all female; reproduce via _________________. Diploid or triploid eggs develop directly from oocytes (___________________), no cellular/nuclear division. At meiosis, identical rather than homologous chromosomes pair, and then segregate. All offspring are females and ____________________ __________________________________. Cnemidophorus species tend to have extremely low levels of genetic diversity. Plants • Hermaphrodite flowers • Hermaphrodite and male flowers on the same plant • Male and Female flowers on the same plant • Male and Female flowers on different plants Genomic Imprinting Differential expression of alleles at a locus depending on whether the allele has been inherited from the mother or the father. Disease can result from imprinting QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Paternal SNRPN gene active-Maternal SNRPN Paternal SNRPN paternally imprinted Gene inactive by Gene inactive by (chrom. 15) imprinting mutation Fertilization Mild retardation Compulsive eating Obesity Diabetes Prader-Willi Syndrome QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Both copies inactive A nearby gene (also on chrom. 15) is maternally imprinted • A mutation in this gene results in Angelman Syndrome: mild retardation, seizures, and involuntary muscle contractions. • Which parent is the mutant allele inherited from in Angelman’s Syndrome?
