genes on the x chromosome:
DESCRIPTION
II. III. XY. IV. or. XX. Genes on the X Chromosome:. *1909 Thomas Hunt Morgan. *Sex chromosomes *Autosomes. Example: In Drosophila and all mammals sex chromosomes designated as X and Y XX=female XY=male. Genes on the X Chromosome con’t:. *X-linkage. X-linkage in Drosophila : - PowerPoint PPT PresentationTRANSCRIPT
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Genes on the X Chromosome:
*Sex chromosomes*Autosomes
Example: In Drosophila and all mammalssex chromosomes designated as X and YXX=femaleXY=male
*1909 Thomas Hunt Morgan
II III IV
XX
XY
or
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*X-linkage
X-linkage in Drosophila: white mutation (eyes)
Genes on the X Chromosome con’t:
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Sex-limited Inheritance:*Sex-limited trait
*holandric genes: genes on the Y chromosome
*autosomal genesExample: milk production in mammals; L=lots, l=little
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*Sex-influenced trait
Sex-influenced Inheritance:
Examples:*cleft palate in humans*horns in sheep *pattern baldness in
humans
Summary:Sex-linked on X or Y sex-chromosomeSex-limited all or none expression by sexSex-influenced genotype + sex determines phenotype
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Phenotypic Expression:
*Penetrance
*Expressivity
Gene expression often governed by genotype and environment
If 9/10 of individuals carrying an allele express the trait, the trait is said to be 90% penetrant
*Onset of genetic expression
*Temperature