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What Is Polygenic Inheritance?

In Drosophila...

Question

In Drosophila, the gene for wing shape (wild type or arc), and the gene for body color (wild type or black) are located on the same chromosome. A test cross was performed between a fly heterozygous for both wing shape and body color with another fly homozygous recessive for both traits. The cross resulted in the numbers of each offspring is as follows
No of Offspring Trait
682 Wild-Type
517 Black
489 Arc
716 Arc-Black
How many linkage map units apart are these two genes?

A

5.8 L M U

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B

42 L M U

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C

58 L M U

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D

It is not possible to determine from the data given

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Solution

The correct option is B $42 L M U$
The distance between the genes is calculated using the number of recombinants. The recombinants are black and arc. So, the distance can be calculated by (total number of recombinants/ total number of progeny) x 100= (517+489/2404) x 100= (1006/2404) x 100= 41.8=42 LMU.
Thus, the correct answer is option B.

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Similar questions

Q. A dominant gene B is responsible for the wild type body color of Drosophila, its recessive allele b produces black body color. A test cross of a wild type female gave 52 black and 58 wild type in the

F_{1}

. If the wild type

F_{1}

females are crossed with black

F_{1}

males, what would be the expected genotypic ratio in the

F_{2}

.

Q. Choose the incorrect statement(s) from the following.
(A) Gene for eye color in Drosophila is located on X-chromosome
(B) Red eye colour is dominant over white eye color
(C) White eye color is considered as wild type
(D) Recessive homozygous condition for eye color is lethal

Q. A cross was done between dominant wild type grey bodied male drosophila melanogaster having developed wing, with recessive mutant yellow bodied female fly having vestigial wing.

F_{1}

offsprings of the above cross were as follows-

(a) All females were of wild type variety with grey body and developed wing

(b) All males were of mutant type with yellow body and vestigial wing

Based on information given above, identify the genotype of parental generation form options given below-

Q. Individual homozygous ab genes were crossed with wild type (++) in Drosophila. The F1 hybrid produced were test crossed. The progenies produced were:
++ = 900
ab = 600
+a = 115
+b = 105
Calculate the recombination frequency for a and b genes:

Q. In Drosophila melanogaster, cherub wings

(c h (

(b)

and cinnabar eyes

(c n)

are recessive to their corresponding alleles (represented as

c h +, b +

c n +

, respectively) and are all located on chromosomes

2

. Homozygous wild type flies were mated with cherub, black and cinnabar flies and the resulting

F 1

females were test crossed with cherub, black and cinnabar males. The following progeny were produced from the test cross:

$c h b + c n$	$110$
$c h + b + c n +$	$780$
$c h + b c n$	$70$
$c h + b + c n$	$6$
$c h b c n$	$769$
$c h b + c n +$	$60$
$c h + b c n +$	$111$
$c h b c n +$	$9$
Total	$1915$

Of these three genes, which one is in the middle?

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