1. In the snail Cepaea nemoralis, an autosomal allele causing a banded shell (b)

Question

1. In the snail Cepaea nemoralis, an autosomal allele causing a banded shell (b) is recessive to the allele for an unbanded shell (8). Genes at a different autosomal locus determine the background color of the shell: yellow (y) is recessive to brown (V). A true-breeding banded, yellow snail rs crossed with a homozygous brown, unbanded snail. The Fi are then crossed with banded, yellovw snails. a. Write out the F1 cross described above using th independent genes indicated alleles and proper annotation for b. Write out the F1 cross described above using the indicated alleles and proper onnotation for linked genes, Be sure to include genotype AND corresponding phenotypes c. What will the results of the F1 cross described above be if the loci that control banding and color are independent? Be specific regardin genotypes, phenotypes, and proportions d. What will the results of the F1 cross described above be if the loci are completely inked? Be specific regarding progeny genotypes, phenotypes, and proportions

Explanation / Answer

Answer:

a). bbyy (banded, yellow) x BBYY (unbanded, brown)—Parents

                                    BbYy (unbanded, brown)----------F1

b). by/by (banded, yellow) x BY/BY (unbanded, brown)—Parents

                                    BY/ by (unbanded, brown)----------F1

c).

BbYy x BbYy---F1xF1

B_Yy= unbanded, brown (9/16)

B_yy = Unbanded, yellow (3/16)

bbY_ = Banded, brown (3/16)

bbyy = banded, yellow (1/16)

d).

BY/by x BY/by

BY

by

BY

BY/BY (unbanded, brown)

BY/by (unbanded, brown)

by

BY/by (unbanded, brown)

by/by (banded, yellow)

Unbanded, brown (3/4) : banded, yellow (1/4)

BY

by

BY

BY/BY (unbanded, brown)

BY/by (unbanded, brown)

by

BY/by (unbanded, brown)

by/by (banded, yellow)

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