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Ch. 3 - Mendelian Genetics
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of GeneticsISBN: 9780135564776당신이 사용하는 게 아니라요?교과서 변경
3장, 문제 25c

A 'wrongful birth' case was recently brought before a court in which a child with Smith–Lemli–Opitz syndrome was born to apparently healthy parents. This syndrome is characterized by a cluster of birth defects, including cleft palate, and an array of problems with the reproductive and urinary organs. Originally considered by their physician as having a nongenetic basis, the parents decided to have another child, who was also born with Smith–Lemli–Opitz syndrome. In the role of a genetic counselor, instruct the court about what occurred, including the probability of the parents having two affected offspring, knowing that the disorder is inherited as a recessive trait. What is the probability that neither of them is a carrier?

검증된 단계별 안내
1
Step 1: Understand the inheritance pattern of Smith–Lemli–Opitz syndrome. It is a recessive genetic disorder, meaning that an individual must inherit two copies of the defective allele (one from each parent) to express the condition. Carriers have one defective allele and one normal allele but do not show symptoms.
Step 2: Analyze the probability of the parents being carriers. Since both children are affected, each parent must have contributed a defective allele. This confirms that both parents are carriers of the recessive allele.
Step 3: Calculate the probability of the parents having two affected offspring. For each child, the probability of inheriting two defective alleles from carrier parents is 25% (1/4). Since the events are independent, multiply the probabilities for two children: \( P(affected) = (1/4) \times (1/4) \).
Step 4: Determine the probability that neither parent is a carrier. If neither parent is a carrier, they cannot produce affected offspring. However, since both children are affected, the probability that neither parent is a carrier is 0%.
Step 5: Use a Punnett square to visualize the inheritance pattern. For two carrier parents (genotype Aa), the possible offspring genotypes are: AA (normal, 25%), Aa (carrier, 50%), and aa (affected, 25%). This confirms the probabilities calculated in Step 3.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Recessive Inheritance

Recessive inheritance occurs when a trait is expressed only when an individual has two copies of the recessive allele. In the case of Smith–Lemli–Opitz syndrome, which is inherited as a recessive trait, both parents must carry one copy of the mutated gene for their child to be affected. If both parents are carriers, there is a 25% chance with each pregnancy that their child will inherit the disorder.
추천 영상:
가이드 코스
05:13
Organelle Inheritance

Carrier Probability

The probability of being a carrier for a recessive genetic disorder can be calculated using the principles of Mendelian genetics. If both parents have one affected child, the likelihood that they are both carriers increases. In this scenario, the parents' genotypes can be analyzed to determine the probability that neither is a carrier, which is essential for understanding the risk of having another affected child.
추천 영상:

Punnett Square

A Punnett square is a diagram used to predict the genetic makeup of offspring from a cross between two parents. It visually represents the possible combinations of alleles that can result from the parents' genotypes. In this case, constructing a Punnett square for the parents' genotypes can help determine the probabilities of their children being affected by Smith–Lemli–Opitz syndrome, including the likelihood that neither parent is a carrier.
추천 영상:
가이드 코스
18:27
Chi Square Analysis
관련 실천
교과서 질문

A 'wrongful birth' case was recently brought before a court in which a child with Smith–Lemli–Opitz syndrome was born to apparently healthy parents. This syndrome is characterized by a cluster of birth defects including cleft palate, and an array of problems with the reproductive and urinary organs. Originally considered by their physician as having a nongenetic basis, the parents decided to have another child, who was also born with Smith–Lemli–Opitz syndrome. In the role of a genetic counselor, instruct the court about what occurred, including the probability of the parents having two affected offspring, knowing that the disorder is inherited as a recessive trait. What is the probability that one of them is a carrier and the other is not? [Hint: The p values in (b), (c), and (d) should equal 1.]

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교과서 질문

Datura stramonium (the Jimsonweed) expresses flower colors of purple and white and pod textures of smooth and spiny. The results of two crosses in which the parents were not necessarily true breeding are shown below. Based on these results, put forward a hypothesis for the inheritance of the purple/white and smooth/spiny traits.

482
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교과서 질문

A 'wrongful birth' case was recently brought before a court in which a child with Smith–Lemli–Opitz syndrome was born to apparently healthy parents. This syndrome is characterized by a cluster of birth defects including cleft palate, and an array of problems with the reproductive and urinary organs. Originally considered by their physician as having a nongenetic basis, the parents decided to have another child, who was also born with Smith–Lemli–Opitz syndrome. In the role of a genetic counselor, instruct the court about what occurred, including the probability of the parents having two affected offspring, knowing that the disorder is inherited as a recessive trait. Calculate the probability that both the male and female are carriers for TSD.

477
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교과서 질문

Datura stramonium (the Jimsonweed) expresses flower colors of purple and white and pod textures of smooth and spiny. The results of two crosses in which the parents were not necessarily true breeding are shown below. Assuming that true-breeding strains of all combinations of traits are available, what single cross could you execute and carry to an F₂ generation that will prove or disprove your hypothesis? Assuming your hypothesis is correct, what results of this cross will support it?

831
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교과서 질문

A 'wrongful birth' case was recently brought before a court in which a child with Smith–Lemli–Opitz syndrome was born to apparently healthy parents. This syndrome is characterized by a cluster of birth defects including cleft palate, and an array of problems with the reproductive and urinary organs. Originally considered by their physician as having a nongenetic basis, the parents decided to have another child, who was also born with Smith–Lemli–Opitz syndrome. In the role of a genetic counselor, instruct the court about what occurred, including the probability of the parents having two affected offspring, knowing that the disorder is inherited as a recessive trait.

496
views
교과서 질문

A 'wrongful birth' case was recently brought before a court in which a child with Smith–Lemli–Opitz syndrome was born to apparently healthy parents. This syndrome is characterized by a cluster of birth defects including cleft palate, and an array of problems with the reproductive and urinary organs. Originally considered by their physician as having a nongenetic basis, the parents decided to have another child, who was also born with Smith–Lemli–Opitz syndrome. In the role of a genetic counselor, instruct the court about what occurred, including the probability of the parents having two affected offspring, knowing that the disorder is inherited as a recessive trait. Draw a pedigree of the families of this couple, showing the relevant individuals.

722
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