3) (12 pts) Male C. elegans expressing the recessive mutations l (long), r (roll

Question

3) (12 pts) 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

653 : u t r l : male parent

675 : ++++ : female parent

670 : + t r l

655 : u +++

73 : u++l

71 : +++l

73 : u r t +

74 : + r t +

88 : u r + l

83 : + r + l

85 : u + t +

84 : ++ t +

1 : u + t l

1 : ++ t l

1 : u r ++

1 : + r ++

a) Genotype of the female parent : Dominant alleles : URTL or ++++

b) Compare two point crosses :

Map distance :

Distance between u and t : 670 + 655 + 73 + 74 + 88 + 84 + 1 + 1= 1646 /3288 = 0.5 m.u

Distance between u and r : 670 + 655 + 73 + 74 + 83 + 85 + 1 +1 = 1642/ 3288 = 0.499 m.u

Distance between u and l : 670 + 655 + 71 + 73 + 83 + 85 + 1 + 1 = 1639/3288 = 0.498 m.u

Distance between t and r : 88 + 83 + 85 + 84 + 1 + 1 + 1 + 1 = 344/ 3288 = 0.104 m.u

Disatnce between t and l : 73 + 71 + 73 + 74 + 83 + 85 + 84 + 88 = 631/3288 = 0.191 m.u

Distance between r and l : 73 + 71 + 73 + 74 + 1 + 1 + 1 +1 = 295/3288 = 0.089 m.u

Map position : u l r t

c) Interference = 1- coefficient of coincidence

Number of double recombinants / 3288

4 / 3288 = 1.217 x 10 -3 x 100 = 0.1217

0.1217 x 3288 = 400 (expected recombinants)

4/400 = 0.01 = coefficient of coincidence

Interference = 1 - 0.01 = 0.99 x 100 = 99 %

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