Lecture 7 (deleted 4f50fb8f-1dc8ae-5a2a49fd)

The sex of this fruixly is because

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Unformatted text preview: lt;0.5 = metamale Genic balance system: determined by the X to A ra1o 25 Chromosomal sex determina1on in C. elegans XX = hermaphrodite (2 X chromosomes) XO = male (1 X chromosome) The number of X chromosomes determines sex 26 13 2/14/12 Chromosomal sex determina1on in birds and buterflies* *plus snakes, some amphibians and some fishes Female is heterogame1c: ZW Male is homogame1c: ZZ Summary: Independent evolu1on of chromosomal sex determina1on 27 Gynandromorphs A gynandromorph is an organism that contains both male and female characteris1cs Sexual Mosaics 28 14 2/14/12 ‘Chromosomal’ sex determina1on in hymenopteran Note: A male has no father and cannot have sons, but he has a grandfather and can have grandsons Haplodiploid sex determina1on is prevalent in eusocial insects 29 Concept check 2: A fruixly is found that has three sex chromosomes (XXY) and three of each autosome (AAA). The sex of this fruixly is ________ because ___________. A. male; it has a Y chromosome. B.  female; it has 2 X chromosomes. C.  female; it has a 1:1 ra1o of sex chromosomes to autosomes. D. intersex; it has an X:A ra)o between 0.5 and 1. E.  female; it is diploid. F.  Impossible to determine; sex is influenced by environment. Sex determina)on = The mechanism by which sex is specified. Sex can be determined by differences in chromosomes, genotypes or environment. 30 15 2/14/12 Genic sex determina1on *and some plants, fungi and protozoan No visible sex chromosomes: genotypes at one or more loci determine sex 31 Environmental sex determina1on Dominant individual = female Time Time Lower temp = male Temperature (during embryogenesis) Loca)on (sequen1al hermaphrodi1sm) Dominant individual = male Social context (can chan...
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This note was uploaded on 01/30/2013 for the course BIO LS1B taught by Professor Andrewberry,hopihoekstra,maryellenruvolo during the Spring '12 term at Harvard.

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