( GENETICS problems 20, 21, & 28--Explain solutions, please ) tall F, plant is b
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( GENETICS problems 20, 21, & 28--Explain solutions, please )
tall F, plant is backcrossed to the tall parent? De produced i b. c. Ai d. Two of the same n e. An even number on both dice 20. Joe has a white cat named Sam. When Joe crosses Sam with a black cat, he obtains /, white kittens and '/, black kittens. When the black kittens are interbred, all the kittens that they produce are black. On the basis of these results, would you conclude that white or black coat color in cats is a recessive trait? Explain your reasoning. two is, or two 2s, or two 3s, etc.) f. An even number on at least one die 27. In a family of seven children, what is the probability of obtaining the following numbers of boys and girls? a. All bovs b. All children of the same sex c. Six girls and one boy d. Four boys and three girls e. Four girls and three boys 21. In sheep, lustrous fleece results from an allele (L) that is dominant over an allele () for normal fleece. A ewe (adult female) with lustrous fleece is mated with a ram (adult male) with normal fleece. The ewe then gives birth to a single lamb with normal fleece. From this single offspring, is it possible to determine the genotypes of the two parents? If so what are their genotypes? If not, why not? 28. Phenylketonuria (PKU) is a disease that results from a recessive gene. Suppose that two unaffected parents produce a child with PKU a. What is the probability that a sperm from the father will contain the PKU allele? Jeffrey van Daele FeaturePics b. What is the probability that an egg from the mother will contain the PKU allele? 22. Alkaptonuria is a metabolic disorder in which affected people produce black urine. Alkaptonuria results from an allele (a) that is recessive to the allele for normal metabolism (A). Sally has normal metabolism, but her brother has alkaptonuria. Sally's father has alkaptonuria, and her mother has normal metabolisnm c. What is the probability that their next child will have PKU? d. What is the probability that their next child will be heterozygous for the PKU gene? 29. In German cockroaches, curved wings (cv) are recessive having to normal wings (cv). A hoExplanation / Answer
20. According to the information given Black coat color is recessive. Because when Sam was crossed with black cat Joe one half of the progeny were white and one half were black. This indicates that one of the parents is heterozygous dominant while the other will be homozygous recessive. But when the black kittens were interbred they produced only black kittens which suggest that black coat color is recessive. If black coat color was dominant the black kittens in the first generation would be heterozygous and if this was the condition inbreeding of black kittens will produce one -fourth progeny of the white kittens.
21. Yes, it is possible to determine the genotype of the parents. Let's assume that the dominant lustrous fleece exhibit completer penetrance. As both the ram and the single lamb have normal fleece (l) it must be homozygous(l) for the normal fleece allele. As the lamb receives one copy of normal allele from ram the other copy should come from the ewe. This suggests that ewe is heterozygous for lustrous fleece.
Ll X ll
Ll (50%) and ll (50%)
28. a. There are 50% chances that the sperm from father contains the PKU allele
b. There are 50% chances that the egg from mother contain the PKU allele
C. As both parents have 1/2 chances of having this mutation so there are 1/4 chances of having a child with PKU.
d. As both parents have 1/2 chances of contributing to the mutant gene and 1/2 chance of donating the healthy gene so there are 50% chances of having a heterozygous child.
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