Question

4. A snail whose shell coils to the left undergoes self-fertilization. All the progeny have shells that coil to the right. (a) What was the genotype of the left-coiling snail's mother? (2 pts) (b) What is the genotype of the left-coiling snail? (2 pts) (C) If the right-coiling progeny are individually self-fertilized, what phenotypes are expected in their progeny (generation 2) and in what frequencies? (2 pts)

Answer 1

let us look at the given picture.

S's SS Dedral Sinistra s Egg S Sperm Sinistra S Ege S's Dextrala S Sperm Fig 18.5 Matemal effect in direction of coiling of the shell in Linnea

(a) The sinistral female egg is the mother and the genotype of the left coiling mother is SS that is sinistral homozygous. as mother's genotypes govern offspring's phenotype.

(b) The genotype of the offspring will be SS* heterozygous because the progeny is right coiling.

(c) the genotype of right coiling snail must be SS* upon self-fertilization it must give 2 SS, SS* and 1 S*S*

so the frequrncy will be 3:1