Ch. 5 - Genetic Linkage and Mapping in Eukaryotes

Sanders - Genetic Analysis: An Integrated Approach 3rd Edition

Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172당신이 사용하는 게 아니라요?교과서 변경

Sanders 3rd Edition

Ch. 5 - Genetic Linkage and Mapping in Eukaryotes

문제 34c

5장, 문제 34c

The accompanying pedigree below shows a family in which an autosomal recessive disorder is present. Family members I-2 and II-2 are affected by the disorder and have the genotype dd. A pregnancy involving II-4 has just undergone genetic testing for a VNTR that is linked to the disease gene. The VNTR has a recombination frequency of r = 20 with the disease gene. The VNTR has two alleles, V₁ and V₂. The gel electrophoresis patterns for each family member are shown, including the VNTR genotype for II-4. Based on the information given, answer the following questions about the family.

What are the syntenic disease gene and VNTR alleles in I-1 and I-2?

검증된 단계별 안내

Step 1: Analyze the pedigree chart to identify the inheritance pattern of the autosomal recessive disorder. Individuals I-2 and II-2 are affected, indicating they are homozygous recessive (dd). The disorder is autosomal recessive, meaning unaffected individuals can be carriers (Dd).

Step 2: Examine the gel electrophoresis results to determine the VNTR genotypes for each family member. VNTR alleles are labeled as V₁ and V₂. For example, I-1 has the genotype V₁V₂, and I-2 has the genotype V₁V₁.

Step 3: Determine the linkage between the VNTR alleles and the disease gene. The recombination frequency (r = 0.20) indicates that the VNTR is linked to the disease gene but not perfectly. This means that VNTR alleles can be used as markers to predict the inheritance of the disease gene.

Step 4: Identify the syntenic VNTR alleles associated with the disease gene in I-1 and I-2. Since I-2 is affected (dd) and has the VNTR genotype V₁V₁, the V₁ allele is likely syntenic with the disease gene. I-1 is unaffected (Dd) and has the VNTR genotype V₁V₂, suggesting that V₁ is linked to the recessive allele (d), while V₂ is linked to the dominant allele (D).

Step 5: Use the VNTR genotypes and recombination frequency to predict the inheritance of the disease gene in II-4. Analyze II-4's VNTR genotype from the gel electrophoresis results and compare it to the parental genotypes to assess the likelihood of inheriting the disease gene.

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주요 개념

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

Autosomal Recessive Inheritance

Autosomal recessive inheritance occurs when a trait or disorder is expressed only when an individual has two copies of the recessive allele (e.g., 'dd'). In this case, individuals I-2 and II-2 are affected by the disorder, indicating they possess the recessive genotype. Carriers, who have one dominant and one recessive allele (e.g., 'Dd'), do not express the disorder but can pass the recessive allele to their offspring.

Variable Number Tandem Repeats (VNTR)

VNTRs are repeating sequences of DNA that vary in length among individuals. They are useful in genetic mapping and can serve as markers for linkage analysis. In this scenario, the VNTR alleles V₁ and V₂ are linked to the disease gene, and their recombination frequency (r = 20) indicates the likelihood of crossover events occurring between the VNTR and the disease gene during meiosis.

Gel Electrophoresis

Gel electrophoresis is a laboratory technique used to separate DNA fragments based on their size. In the context of this question, the gel shows the VNTR genotypes of family members, allowing for the identification of alleles present in each individual. By analyzing the banding patterns, one can infer the genotypes of II-4 and other family members, which is crucial for understanding inheritance patterns and potential disease risk.

관련 실천

교과서 질문

DNA sequences for 10 individuals are

Identify the haplotype carried by each person.

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교과서 질문

Based on previous family studies, an autosomal recessive disease with alleles A and a is suspected to be linked to an RFLP marker. The RFLP marker has four alleles, R₁, R₂, R₃, and R₄. The accompanying pedigree shows a three-generation family in which the disease is present. The gel shows the RFLP alleles for each family member directly below the pedigree symbol for that person. After determining the genotypes for the RFLP and disease gene for each family member, answer the following questions.

Is there any evidence of recombination in this pedigree? If so, identify the recombinant individuals and illustrate the recombination that has occurred.

478

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교과서 질문

What is the most likely arrangement of syntenic alleles for the RFLP and the disease gene in I-1 and I-2?

854

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교과서 질문

The accompanying pedigree below shows a family in which an autosomal recessive disorder is present. Family members I-2 and II-2 are affected by the disorder and have the genotype dd. A pregnancy involving II-4 has just undergone genetic testing for a VNTR that is linked to the disease gene. The VNTR has a recombination frequency of r = 20 with the disease gene. The VNTR has two alleles, V₁ and V₂. The gel electrophoresis patterns for each family member are shown, including the VNTR genotype for II-4. Based on the information given, answer the following questions about the family.

What is the genotype of each family member, including II-4, for the VNTR?

625

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교과서 질문

Excluding II-4, what is the genotype of each family member for the disease gene?

1323

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교과서 질문

What is the chance II-4 has the disease?

516

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