26. Since each child of two heterozygous parents has a 50% chance of receiving a recessive trait from each parent, A. if the first child is phenotypically recessive, then the next child must be phenotypically dominant. B. if the first child is phenotypically recessive, then the next child has a 3/4 chance of being phenotypically recessive. C. if the first child is phenotypically recessive, then the next child has a 1/2 chance of being phenotypically recessive. D. no matter what the first child’s phenotype, the next child will have a 1/4 chance of being phenotypically recessive. 27. The ability to roll the edges of the tongue upward in a U-shape has been considered to be an inherited ability. The standard assumption is that tongue-rolling is a dominant allele at a single gene locus. Which of the following would cast doubt on this assumption? A. A teacher reports that after testing her class on the ability to roll their tongue, with very little effort the non-tongue-rollers can learn to also roll their tongues. B. A student who can roll his tongue has a mother and father, both of whom cannot. C. A student who cannot roll his tongue has a mother and father, both of whom can. D. Two of the above are situations that would cast doubt on this assumption. 28. If the probability of event A is 3/4 and the probability of event B is 1/4, then the probability of both A and B occurring at the same time is A. 3/4. B. 1/4. C. 1 or absolute certainty. D. 1/2. E. 3/16. 29. The reason why some individuals who inherit polydactyly (having an extra digit on the hand or feet) but do not express the trait is due to ________. A. incomplete penetrance B. incomplete dominance C. gene linkage D. pleiotropy E. none of the answers are correct 30. Computer simulations are sometimes used to demonstrate the outcome of monohybrid fruit fly crosses, where a student can run generation after generation of fruit flies with 100 offspring produced each generation, half male and half female, and a 3-to-1 phenotype ratio (or 75 to 25) in the F1 generation. Compared with real genetics results, A. rarely would exactly 100 fly offspring be produced or survive. B. an exact balance between males and females would be rare. C. a precise 3-to-1 ratio would be uncommon. D. All of the choices are true. Â Â