Shell coiling of the snail Lymnaea peregra results from a genetic maternal effec

Question

Shell coiling of the snail Lymnaea peregra results from a genetic maternal effect. An autosomal allele for Map dst right-handed shell, s, called dextral, is dominant over the allele for a left-handed shell, s, called sinistral. In ral, snails are hermaphroditic and reproduce as both males and females. However, a pet snail named Martha is sinistral and reproduces only as a female Marthas dad Martha's mom Sinistral Dextral Martha Dextral O Sinistral Sinistral sinistral Sinistral Sinistral Sinistral Dextral Dextral Dextral From the pedigree above, determine Martha's, her mother's, and her father's genotypes. Place the genotype next to the individuals listed below the pedigree Martha's genotype Martha's mom's genotype Martha's dad's genotype Continued beloww unknown S'S

Explanation / Answer

Dextral-right handed is dominant shell (s+) over sinistral-left handed shell (s)

so following genotypes will show phenotypes like mentioned below

s+s+ = Dextral - right handed

s+s/ ss+ = Dextral - right handed = mom

ss = Sinistral - left handed = dad of martha and also martha

Let's draw a punnett square

Martha and her sibling is sinistral so both have genotype (ss)

Martha's dad is also sinistral = so genotype (ss)

Martha's mom is dextral so genotype will be (s+s)

but not s+s+ because if this will happen, then none of the offspring will be sinistral.

s+ s s s+s (Dextral) ss (sinistral) s s+s (Dextral) ss (sinistral)

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