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Expected Phenotypes of F2 Cross - Sex-linked Traits (XY system) |
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Genotypic Arrays for Sex-Linked traits in the XY system for all four F2 generations. (Y chromosomes shown for completeness.) |
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| Mother | Father | X--linked (female) | Y-linked (male) | ||
| F2 | F1 | x | F1 | 1/2X1X1:1/2X1X2 | 1/2X1Y2:1/2X2Y2 |
| F2 ' | F1' | x | F1' | 1/2X1X2:1/2X2X2 | 1/2X1Y1:1/2X2Y1 |
| F2 '' | F1 | x | F1' | 1/2X1X2:1/2X2X2 | 1/2X1Y2:1/2X2Y2 |
| F2 ''' | F1' | x | F1 | 1/2X1X1:1/2X1X2 | 1/2X1Y2:1/2X2Y2 |
For X-linked traits in the XY system, the four possible F2 crosses give different genotypic and different phenotypic arrays. This is particularly pronounced if the Y-chromosome plays a role in the phenotype.
Example 1: Complete dominance: Consider a system where red eyes X1 are dominant to white eyes X2.
| Reminder: the F1 cross is a mating of P1
female (X1X1) by a P2 male (X2Y2).
The females in the F1 generation have the genotype X1X2
and the males have the genotype X1Y2. The F1' cross is a mating of P2 female (X2X2) by a P1 male (X1Y1). The females in the F1 generation have the genotype X1X2 and the males have the genotype X2Y1. |
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Genotypic Arrays and Phenotypic Arrays for Sex-Linked traits in the XY system. Complete Dominance (Y chromosome not shown) |
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| Gen | Genotypic
Array X--linked (female) |
Genotypic
Array Y-linked (male) |
Phenotypic
Array females |
Phenotypic
Array Males |
| F2 | 1/2X1X1:1/2X1X2 | 1/2X1:1/2X2 | 100% Red | 1/2 Red: 1/2 White |
| F2 ' | 1/2X1X2:1/2X2X2 | 1/2X1:1/2X2 | 1/2 Red: 1/2 White | 1/2 Red: 1/2 White |
| F2 '' | 1/2X1X2:1/2X2X2 | 1/2X1:1/2X2 | 1/2 Red: 1/2 White | 1/2 Red: 1/2 White |
| F2 ''' | 1/2X1X1:1/2X1X2 | 1/2X1:1/2X2 | 100% Red | 1/2 Red: 1/2 White |
Example 2: Incomplete Dominance
This is best shown by example: Let blue wings be incompletely dominant to yellow wings. The heterozygote would be green wings. The Y-chromosome has no effect on wing color. The results are given below for the four F2 crosses.
| Gen | Genotype X--linked (female) | Genotype Y-linked (male) |
Phenotype-females | Phenotype males |
| F2 | 1/2X1X1:1/2X1X2 | 1/2X1Y2:1/2X2 | 1/2 Blue:1/2 green | 1/2 Blue: 1/2 Yellow |
| F2 ' | 1/2X1X2:1/2X2X2 | 1/2X1Y1:1/2X2 | 1/2 Green: 1/2 Yellow | 1/2 Blue: 1/2 Yellow |
| F2 '' | 1/2X1X2:1/2X2X2 | 1/2X1Y2:1/2X2 | 1/2 Green: 1/2 Yellow | 1/2 Blue: 1/2 Yellow |
| F2 ''' | 1/2X1X1:1/2X1X2 | 1/2X1Y2:1/2X2 | 1/2 Blue:1/2 green | 1/2 Blue: 1/2 Yellow |
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Quick Links F2 Cross |
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| 1 | Basic F2 cross - autosomal genes |
| 2 | Basic F2 cross- X-linked gene |
| Expected Phenotypes of F2 Cross - Single Autosomal Traits | |
| Expected Phenotypes of F2 Cross - X-linked gene | |
| 4 | F2 cross - two unlinked autosomal genes |
| 5 | F2 cross - one autosomal - one X-linked gene |
| 6 | Linkage - Coupling and Repulsion |
| 7 | F2 cross - two linked autosomal genes -coupling |
| 8 | F2 cross - two linked autosomal genes - repulsion |
| 9 | Measuring the recombination rate from F2 data |
| Recombination from F2 data - Table of Values | |
| 10 | Basic F2 cross- Z-linked gene (inactive) |
| 12 | Expected Phenotypes of F2 Cross - Z-linked gene (inactive) |
| 13 | F2 cross - one autosomal - one Z-linked gene (inactive) |
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Also See |
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| Detection of Linkage - Basic Info - Two Autosomal Traits - Complete Dominance | |
| Detection of Linkage - More complex examples | |
| Detection of Linkage - One More Example | |
| Detection of Linkage - Two Autosomal Traits - Heterozygote has Unique Phenotype | |
| Home page | |
| Detailed List for Mendelian Genetics | |