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In a dihybrid cross, white-eyed, yellow ...

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

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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 Morgans.s experiment, the genes for eye and body colour show linkage and do not always allow crossing to over during gamete formation. Hence, parental type progeny is in greater ratio than that of recombinants
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The total number of progeny obtained from a dihybrid cross is 1280 in F_2 -generation . How many of them arc recombinant type ?

Assertion : When yelow bodied, white eyed Drosophila females were hybridised with brown-bodied, red eyeed males , and F_(1) progeny was intercrossed, F_(2) ratio deviated from 9:3:3:1 Reason : When two genes in a dihybrid are on same chromosome, the proportion of parental gene combinations are much higher than the non-parental type

Morgan hybridised yellow-bodied, white-eyed females to brown-bodied red-eyed males and intercrossed their F_(1) progeny. He observed that (a) F_(2) ratio was deviated very significantly from the 9:3:3:1 ratio (b) Both genes did not segregate independently of each other (c) Recombinant types are not obtained in F_(2) generation (d) Both genes segregate independently of each other Select the correct set of statements :

During his studies on genes in Drosophila that were sex-linked, TH Morgan found F_(2) - population phenotypic ratio to be deviated from expected 9 : 3 : 3 : 1 . Explain the conclusion he arrived at

In maize, coloured endosprem (C) is dominant over colourless (c) , and full endosperm (R) is dominant over shrunken (r). When a dihybrid of F_(1) generation was test crossed, it produced four phenotypes in the following percentage : Coloured full - 48 % Coloured shrunken - 5 % Colourless full - 7 % Colourless shrunken - 40 % From this data, what will be the distance between two non-allelic genes ?

True-breeding red-eyed Drosophila flies with plain thoraxes were crossred with pink-eyed flies with striped thoraxes {:("Red eye",xx,"Pink eye"),("Plain thorx",,"striped throrax"):} The F_(1) flies were then test crossed against the double recessive The following F_(2) generation resulted from the cross : {:(80,16,12,92),("Red eye","Red eye","Pink eye","Pink eye"),(underset("thorax")("Plain"),underset("thorax")("Striped"),underset("thorax")("Plain"),underset("thorax")("Striped")):} What percentage number of recombinats resulted from the test cross ?

ARIHANT PUBLICATION-HEREDITY AND VARIATION-Part II Questions For Practice (Short Answer Type Questions )
  1. Two heterozygous parents are crossed . If the two loci are linked, wh...

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  2. Explain two situations, when independent assortment of genes occurs,...

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  3. In a dihybrid cross, white-eyed, yellow -bodied female Drosophila was ...

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  4. How do biologists use cross over frequencies to map genes on chromoso...

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  5. Explain the phenomenon of multiple allelism and codominance taking ...

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  6. What is the phenotype of the following (a) l^(A) i (b) ii

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  7. A child has blood group O. If the father has blood group A and mother ...

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  8. Explain the following What is the most common example of pleiot...

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  9. Explain the following How are the pleiotropic genes useful ?

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  10. State the significance of crossingover.

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  11. What is Chiasma ?

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  12. What is likage? mention it's Significance.

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  13. Write a short notes on: Crossing over

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  14. Define multiple allelism

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  15. During his studies on genes in Drosophila that were sex-linked, TH ...

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  16. List three different allelic forms of gene 'I' in human . Explain th...

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  17. A woman with blood group 'A' marries a man with blood group 'O' . Di...

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  18. A woman with blood group 'A' marries a man with blood group 'O' . Di...

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  19. blood group are called universal recipient.

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  20. Explain ABO blood group?

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