Concept explainers
The ability of humans to taste the bitter chemical phenylthiocarbamide (PTC) is a genetic trait. People with at least one copy of the normal, dominant allele of the PTC gene can taste PTC; those who are homozygous for a mutant, recessive allele cannot taste it. Could two parents able to taste PTC have a nontaster child? Could nontaster parents have a child able to taste PTC? A pair of taster parents, both of whom had one parent able to taste PTC and one nontaster parent, are expecting their first child. What is the chance that the child will be able to taste PTC? Unable to taste PTC? Suppose the first child is a nontaster. What is the chance that their second child will also be unable to taste PTC?
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Chapter 12 Solutions
Biology: The Dynamic Science (MindTap Course List)
- A certain type of deafness in humans is inherited as an X-linked recessive trait. A man with this type of deafness married a normal woman, and they are expecting a child. They find out that they are distantly related. Part of the family tree is shown here.How would you advise the parents about the probability of their child being a deaf boy, a deaf girl, a normal boy, or a normal girl? Be sure to state any assumptions that you make.arrow_forwardThe ability to detect the bitter taste of Phenylthiocarbamide (PTC) is inherited. “Tasting” is controlled by a dominant allele, while “non-tasting” is recessive PTC paper placed in your mouth can determine if you are a “taster” or a “non-taster”? Let's assume that you are a "taster". What possible genotypes could produce your phenotype? If you produced children with a "non-taster", what genotypic and phenotypic ratios would be expected in your offspring?arrow_forwardIn humans, dark hair (D) is dominant over blondness (d), and color blindness (c) is a sex-linked recessive trait. A woman has a blond brother, a blond mother, and a dark-haired father. Her brother and her parents have normal vision. She bears the following three children by her blond, normal-visioned husband: a dark-haired son with normal vision, a dark-haired daughter with normal vision, and a dark-haired color blind son. Make a pedigree of the entire family showing the probable genotypes of all individuals.arrow_forward
- In humans, dark hair (D) is dominant over blondness (d), and color blindness (c) is a sex-linked recessive trait. A woman has a blond brother, a blond mother, and a dark-haired father. Her brother and her parents have normal vision. She bears the following three children by her blond, normal-visioned husband: a dark-haired son with normal vision, a dark-haired daughter with normal vision, and a dark-haired color blind son. What is the probability that her next (fourth) child will be a colorblind boy.arrow_forwardSickle cell anemia is a blood disorder that is expressed with incomplete dominance. The homozygous recessive phenotype has sickle shaped red blood cells that cause anemia and often death if untreated. If an unaffected father and mother move to the United States from Sub-Saharan Africa and several of their offspring have sickle cell anemia, what do we know about both parents' genotypes? One is homozygous recessive, the other is heterozygous They are both heterozygous They are both homozygous recessive One is homozygous dominant, the other is heterozygousarrow_forwardAs shown in the Punnett square below, one variety of deafness is caused by an autosomal recessive allele. Two parents who do not show any signs of the disease but are carriers could therefore have a child who is deaf, because that child could inherit one recessive deafness-causing gene from each parent. Imagine that a deaf male mates with a hearing female. We know the deaf male must have the genotype dd, but the female could be either Dd or DD. Such a mating is essentially a testcross, like the one shown in Figure 9.10. If the parents’ first child has hearing, can you say with certainty what the mother’s genotype must be? What if the couple has four children (none twins), all with hearing—can you say with certainty the mother’s genotype? What would it take for a definitive genotype to be assigned?arrow_forward
- In Humans, the ability to taste PTC is inherited as a dominant gene (T). In a marriage between 2 heterozygous tasters (Tt): (1) what is the probability of 3 taster children, (2) what is the probability of 3 taster girls, (3) Why is there a difference in the last two answers to this problem?arrow_forwardFor a recessive condition, two normal heterozygous individuals have children. What is the likelihood of their children being affected by this condition? What is the likelihood of their children being carriers without the condition? What is the likelihood of their asymptomatic children being carriers? Suppose that an individual with the condition has children with a heterozygous individual, what is the likelihood of their children being carriers?arrow_forwardAs seen in the photo, Labradors come in three colors-- black, brown and yellow. What is the genetic basis for these different coat colors? One gene produces melanin, a pigment which is deposited in the dog's fur and makes the color dark. With this gene, allele B (black) is dominant to allele b. Only in the case of a recessive homozygote (bb) will the dog's phenotype be brown. The regulatory gene is separate from the melanin gene but it acts as a switch, either turning the melanin gene on or turning it off. Allele E is dominant and allows for the melanin to be deposited in the dog's fur ("on" switch), but if the switch gene is a recessive homozygote, the melanin is blocked ("off" switch) and a yellow dog is the result! 1. Two other Labradors mate and produce puppies. Their genotypes are Bbee and BbEe. What color are each parent and what are the phenotypic rations of their offspring in the F1 Generation? Show your work with a Punnett square.arrow_forward
- Marfan syndrome is a disease caused by a rare dominant allele of the fibrillin-1 gene. Fibrillin-1 is an important component of the extracellular matrix, and people with the disease-causing allele have abnormal connective tissue. An affected mother (Marta) and an unaffected father (Joe) have one unaffected daughter (Luisa - she does not exhibit any traits of the syndrome). If Luisa has a child with Nico (unaffected), what is the probability that her child will inherit Marfan syndrome? Select one: a. 50% b. 25% c. 100% d. 0% e. 75%arrow_forwardHumans who have an abnormally high level of cholesterol are said to suer from familial hypercholesterolemia . The gene for this disorder is dominant (C). A man who is heterozygous for familial hypercholesterolemia marries a woman who is homozygous for the recessive allele. What is the probability that they will have children that suer from this disorder?arrow_forwardThe trait of having short eyelashes is recessive in humans. A male with short eyelashes has two children with a female. One child has short eyelashes and the other has the long eyelash phenotype. What are the genotypes of the two parents?arrow_forward
- Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage Learning