In a dihybrid cross, white eyed, yellow bodied female Drosophila was crossed with red eyed

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principleinheritance

#1

In a dihybrid cross, white eyed, yellow bodied female Drosophila was crossed with red eyed, brown bodied male Drosophila, produced in $F_{ 2 }$- generation are 1.3% recombinants and 98.7% progeny with parental type combinations. This observation of Morgan deviated from Mendelian $F_{ 2 }$-phenotypic dihybrid ratio. Explain, giving reasons, Morgan’s observations.


#2

Morgan saw that when the two genes in dihybrid cross were situated on same chromosome, the proportion of parental gene combinations were higher than non-parental type. This is due to physical association of genes on a chromosome or linkage. In Morgan’s experiment, the genes for eye and body colour show linkage and do not always allow crossing over during gamete formation. Hence, parental type progeny is in greater ratio than that of recombinants.