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 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 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
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