logging in or signing up Chromosomes III Breezy Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 393 Category: Entertainment License: All Rights Reserved Like it (2) Dislike it (0) Added: August 02, 2007 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript SEX DETERMINATION INDROSOPHILA: SEX DETERMINATION IN DROSOPHILA Drosophila melanogaster also has X and Y chromosomes, with the female being homogametic and the male heterogameticBut Drosophila doesn’t use a Y-determining systemEvidence: XXY fly is femaleXO fly is male : Drosophila melanogaster also has X and Y chromosomes, with the female being homogametic and the male heterogametic But Drosophila doesn’t use a Y-determining system Evidence: XXY fly is female XO fly is male Drosophila uses the X-chromosome-autosome balance system of sex determinationThe sex of the individual depends on the ratio of the number of sets of autosomes to the number of X chromosomes: Drosophila uses the X-chromosome-autosome balance system of sex determination The sex of the individual depends on the ratio of the number of sets of autosomes to the number of X chromosomes Normal female has 2 X’s, and 2 sets of autosomes, for an S:A ratio = 1.00If the X:A ratio is greater than or equal to 1.00, the fly will be female: Normal female has 2 X’s, and 2 sets of autosomes, for an S:A ratio = 1.00 If the X:A ratio is greater than or equal to 1.00, the fly will be female Normal male fly has 1 X, and 2 sets of autosomes, for an X:A ratio = 0.50If the X:A ratio is less than or equal to 0.50, the fly will be male.: Normal male fly has 1 X, and 2 sets of autosomes, for an X:A ratio = 0.50 If the X:A ratio is less than or equal to 0.50, the fly will be male. If the X:A ratio is between 0.50 and 1.00, the fly will be an intersex, and sterile: If the X:A ratio is between 0.50 and 1.00, the fly will be an intersex, and sterile The X chromosome-autosome balance system is not universal in insects, or even in dipterans.The house fly, Musca domestica, uses a Y-determining system just like humansThere are strains of house flies, from nature, in which the male-determining factor has jumped from the Y to an autosome!: The X chromosome-autosome balance system is not universal in insects, or even in dipterans. The house fly, Musca domestica, uses a Y-determining system just like humans There are strains of house flies, from nature, in which the male-determining factor has jumped from the Y to an autosome! The nematode, Caenorhabditis elegans (C. elegans) is currently an important model organism for developmental geneticsIndividuals are either hermaphroditic, or maleThis also uses the X-autosome balance system: The nematode, Caenorhabditis elegans (C. elegans) is currently an important model organism for developmental genetics Individuals are either hermaphroditic, or male This also uses the X-autosome balance system In birds, lepidopterans, and some fish:Male is the homogametic sex, female the heterogametic sexTo prevent confusion, their sex chromsomes are called Z and WMales are ZZ and females are ZW: In birds, lepidopterans, and some fish: Male is the homogametic sex, female the heterogametic sex To prevent confusion, their sex chromsomes are called Z and W Males are ZZ and females are ZW Many unicellular eukaryotes don’t really have sexes, but “mating types”These don’t use sex chromosomes, but have a genic system for specifying mating typeExample: in yeast, Saccharomyces cerevisiae, mating type is determined by the 2 alleles, a and alpha: Many unicellular eukaryotes don’t really have sexes, but 'mating types' These don’t use sex chromosomes, but have a genic system for specifying mating type Example: in yeast, Saccharomyces cerevisiae, mating type is determined by the 2 alleles, a and alpha Environmental Sex Determination SystemsThese are much rarer than the genotypic systems: Environmental Sex Determination Systems These are much rarer than the genotypic systems In the marine worm Bonellia:Free-swimming larvae are undifferentiatedIf one settles alone, becomes a female.If it settles on a female, it becomes a male.: In the marine worm Bonellia: Free-swimming larvae are undifferentiated If one settles alone, becomes a female. If it settles on a female, it becomes a male. In some reptiles, the temperature at which the eggs are incubated determines the sex of the offspring.: In some reptiles, the temperature at which the eggs are incubated determines the sex of the offspring. SEX-LINKED TRAITS IN HUMANS: SEX-LINKED TRAITS IN HUMANS X-Linked RecessiveHave already discussed typical pedigreesExamples:Hemophilia-AFragile-X SyndromeDuchenne Muscular Dystrophy: X-Linked Recessive Have already discussed typical pedigrees Examples: Hemophilia-A Fragile-X Syndrome Duchenne Muscular Dystrophy X-Linked DominantMuch rarer than X-linked recessivesAll of the daughters, and none of the sons of an affected father will be affectedHetero mothers transmit to 1/2 her sons and 1/2 her daughters: X-Linked Dominant Much rarer than X-linked recessives All of the daughters, and none of the sons of an affected father will be affected Hetero mothers transmit to 1/2 her sons and 1/2 her daughters Examples:Faulty tooth enamelWebbing to the tips of the toesConstitutional thrombopathy (inability to form platelets, needed for clotting): Examples: Faulty tooth enamel Webbing to the tips of the toes Constitutional thrombopathy (inability to form platelets, needed for clotting) Y-Linked InheritanceAlso called holandric inheritance, because it passes from male to male, and only occurs in malesStill speculative about existence of holandric traits in humans, other than for maleness itself: Y-Linked Inheritance Also called holandric inheritance, because it passes from male to male, and only occurs in males Still speculative about existence of holandric traits in humans, other than for maleness itself A possible example is “hairy ears”Common in parts of IndiaOther possible explanations, however: A possible example is 'hairy ears' Common in parts of India Other possible explanations, however Slide20: You do not have the permission to view this presentation. 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Chromosomes III Breezy Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 393 Category: Entertainment License: All Rights Reserved Like it (2) Dislike it (0) Added: August 02, 2007 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript SEX DETERMINATION INDROSOPHILA: SEX DETERMINATION IN DROSOPHILA Drosophila melanogaster also has X and Y chromosomes, with the female being homogametic and the male heterogameticBut Drosophila doesn’t use a Y-determining systemEvidence: XXY fly is femaleXO fly is male : Drosophila melanogaster also has X and Y chromosomes, with the female being homogametic and the male heterogametic But Drosophila doesn’t use a Y-determining system Evidence: XXY fly is female XO fly is male Drosophila uses the X-chromosome-autosome balance system of sex determinationThe sex of the individual depends on the ratio of the number of sets of autosomes to the number of X chromosomes: Drosophila uses the X-chromosome-autosome balance system of sex determination The sex of the individual depends on the ratio of the number of sets of autosomes to the number of X chromosomes Normal female has 2 X’s, and 2 sets of autosomes, for an S:A ratio = 1.00If the X:A ratio is greater than or equal to 1.00, the fly will be female: Normal female has 2 X’s, and 2 sets of autosomes, for an S:A ratio = 1.00 If the X:A ratio is greater than or equal to 1.00, the fly will be female Normal male fly has 1 X, and 2 sets of autosomes, for an X:A ratio = 0.50If the X:A ratio is less than or equal to 0.50, the fly will be male.: Normal male fly has 1 X, and 2 sets of autosomes, for an X:A ratio = 0.50 If the X:A ratio is less than or equal to 0.50, the fly will be male. If the X:A ratio is between 0.50 and 1.00, the fly will be an intersex, and sterile: If the X:A ratio is between 0.50 and 1.00, the fly will be an intersex, and sterile The X chromosome-autosome balance system is not universal in insects, or even in dipterans.The house fly, Musca domestica, uses a Y-determining system just like humansThere are strains of house flies, from nature, in which the male-determining factor has jumped from the Y to an autosome!: The X chromosome-autosome balance system is not universal in insects, or even in dipterans. The house fly, Musca domestica, uses a Y-determining system just like humans There are strains of house flies, from nature, in which the male-determining factor has jumped from the Y to an autosome! The nematode, Caenorhabditis elegans (C. elegans) is currently an important model organism for developmental geneticsIndividuals are either hermaphroditic, or maleThis also uses the X-autosome balance system: The nematode, Caenorhabditis elegans (C. elegans) is currently an important model organism for developmental genetics Individuals are either hermaphroditic, or male This also uses the X-autosome balance system In birds, lepidopterans, and some fish:Male is the homogametic sex, female the heterogametic sexTo prevent confusion, their sex chromsomes are called Z and WMales are ZZ and females are ZW: In birds, lepidopterans, and some fish: Male is the homogametic sex, female the heterogametic sex To prevent confusion, their sex chromsomes are called Z and W Males are ZZ and females are ZW Many unicellular eukaryotes don’t really have sexes, but “mating types”These don’t use sex chromosomes, but have a genic system for specifying mating typeExample: in yeast, Saccharomyces cerevisiae, mating type is determined by the 2 alleles, a and alpha: Many unicellular eukaryotes don’t really have sexes, but 'mating types' These don’t use sex chromosomes, but have a genic system for specifying mating type Example: in yeast, Saccharomyces cerevisiae, mating type is determined by the 2 alleles, a and alpha Environmental Sex Determination SystemsThese are much rarer than the genotypic systems: Environmental Sex Determination Systems These are much rarer than the genotypic systems In the marine worm Bonellia:Free-swimming larvae are undifferentiatedIf one settles alone, becomes a female.If it settles on a female, it becomes a male.: In the marine worm Bonellia: Free-swimming larvae are undifferentiated If one settles alone, becomes a female. If it settles on a female, it becomes a male. In some reptiles, the temperature at which the eggs are incubated determines the sex of the offspring.: In some reptiles, the temperature at which the eggs are incubated determines the sex of the offspring. SEX-LINKED TRAITS IN HUMANS: SEX-LINKED TRAITS IN HUMANS X-Linked RecessiveHave already discussed typical pedigreesExamples:Hemophilia-AFragile-X SyndromeDuchenne Muscular Dystrophy: X-Linked Recessive Have already discussed typical pedigrees Examples: Hemophilia-A Fragile-X Syndrome Duchenne Muscular Dystrophy X-Linked DominantMuch rarer than X-linked recessivesAll of the daughters, and none of the sons of an affected father will be affectedHetero mothers transmit to 1/2 her sons and 1/2 her daughters: X-Linked Dominant Much rarer than X-linked recessives All of the daughters, and none of the sons of an affected father will be affected Hetero mothers transmit to 1/2 her sons and 1/2 her daughters Examples:Faulty tooth enamelWebbing to the tips of the toesConstitutional thrombopathy (inability to form platelets, needed for clotting): Examples: Faulty tooth enamel Webbing to the tips of the toes Constitutional thrombopathy (inability to form platelets, needed for clotting) Y-Linked InheritanceAlso called holandric inheritance, because it passes from male to male, and only occurs in malesStill speculative about existence of holandric traits in humans, other than for maleness itself: Y-Linked Inheritance Also called holandric inheritance, because it passes from male to male, and only occurs in males Still speculative about existence of holandric traits in humans, other than for maleness itself A possible example is “hairy ears”Common in parts of IndiaOther possible explanations, however: A possible example is 'hairy ears' Common in parts of India Other possible explanations, however Slide20: