Question

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Use the information below to answer questions 1 - 2. Leatherback turtles (Dermochelys coriacea) lay 50 eggs per clutch on soft sand beaches. Let us assume that the first and second cleavage within the developing eggs is controlled by the presence of a single pair of codominant alleles, CA and CB. Full cleavage and development to maturity will occur if an offspring bears alleles in the heterozygous (CAC) condition. However, there is only 18% cleavage penetrance if CACA appears in the homozygous condition and 23% penetrance if CBCP appears in the homozygous condition. The remaining eggs do not proceed past the second cleavage stage of development. 1. What is the genotypic ratio expected among the F, progeny when turtles with a heterozygous genotype are mated? (1 pt) Phenotypic ratio: 2. Assume that after mating, the female of the cross described in the previous question laid a clutch of 50 eggs. How many of these eggs can be expected to produce live young? (4 pts)

Answer 1

Answer (1): Genotypic ratio    CACA: CACB​: CBCB

1 : 2 : 1

Answer (2): 20 of these eggs can be expected to produce live young.