11Changes in Sex Chromosome Number Y chromosome-determines maleness.SRY gene produces a testis-determining factorCaused by non-disjunction
12Non-disjunction in Sex Chromosomes Y chromosome-determines maleness.Results of non-disjunction?:XXXXXYXYYX00YSurvivable with problemsSurvivable with problemsSurvivable with problemsSurvivable with problemsLethal
13Non-disjunction in Sex Chromosomes Turner Syndrome --XOKlinefelter Syndrome—XXYPoly-X Females---XXXJacobs Syndrome---XYY
14Changes in Chromosome Structure Mutation– a permanent genetic change.Chromosome mutation--change in chromosome structure.Types:InversionTranslocationDeletionDuplication
20Sex-Linked TraitsTraits controlled by genes on the X or Y chromosomes are sex-linked although most are unrelated to gender.An allele on the X chromosome that is in the region where the Y chromosome has no alleles will express even if recessive; it is termed X-linked.A female would have to have two recessive genes to express the trait; a male would only need one.
21X-Linked AllelesThe key for an X-linked problem shows the allele attached to the X as in:XB = normal visionXb = color blindness.Females with the genotype XBXb are carriers because they appear to be normal but each son has a 50% chance of being color blind depending on which allele the son receives.XbXb and XbY are both colorblind.