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 Paternal SNRPN Gene inactive by mutation Paternal SNRPN gene active-- paternally imprinted (chrom. 15) Maternal SNRPN Gene inactive by imprinting Fertilization Both copies inactive Prader-Willi Syndrome Mild retardation Compulsive eating Obesity Diabetes 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 Angelmans Syndrome?