Male C. elegans expressing the recessive mutations l (long), r (rolling), t (tou

Question

Male C. elegans expressing the recessive mutations l (long), r (rolling), t (touch insensitive), and u (uncoordinated) are crossed to phenotypically wild-type females. The phenotypes of the 3288 F2 progeny are shown below.

653    uncoordinated, long, rolling, touch insensitive

670    long, rolling, touch insensitive

675    wild type

655    uncoordinated

73    uncoordinated, long

71    long

73    uncoordinated, rolling, touch insensitive

74    rolling, touch insensitive

88    uncoordinated, long, rolling

83    long, rolling

85    uncoordinated, touch insensitive

84    touch insensitive

1    uncoordinated, long, touch insensitive

1    long, touch insensitive

1    uncoordinated, rolling

1    rolling

a) Diagram the genotype of the female parent.

b) Map the loci (i.e., determine the position and map distances among the genes).

c) Is there evidence of interference? Justify your answer with numbers.

Explanation / Answer

a). The genotype of the female parent would be: LlRrTtUu

b). U is farthest.

Distance between t and u = (675+655)/(3288) x (100) = 40.45 cM

Distance between r and t = (85+84)/ (3288) x 100 = 5.1 cM

Distance between l and r = 9.5 cM

c). Yes, interference happened and is evidenced by formation of double cross over.

llR_T_uu 2%

llR_T_U_ 2%

llrrT_uu 2.5%

llrrT_U_ 2.5%

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