Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

2. Mendel's Laws of Inheritance

Pedigrees

Genetics

2. Mendel's Laws of Inheritance

Pedigrees

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2:05 minutes

Problem 14d

Textbook Question

Nail–patella syndrome is an autosomal disorder affecting the shape of nails on fingers and toes as well as the structure of kneecaps. The pedigree below shows the transmission of nail–patella syndrome in a family along with ABO blood type.

Explain why III-6 has nail–patella syndrome and III-8 does not. Give genotypes for these two individuals.

Verified step by step guidance

Step 1: Understand the inheritance pattern of nail–patella syndrome. Nail–patella syndrome is an autosomal dominant disorder, meaning that only one copy of the dominant allele is required for an individual to express the trait. If a parent has the disorder, there is a 50% chance of passing it to their offspring.

Step 2: Analyze the pedigree provided. Look at the family tree to determine which individuals have nail–patella syndrome and which do not. Identify the inheritance pattern and note whether III-6 and III-8 inherited the dominant allele associated with the disorder.

Step 3: Determine the genotype for nail–patella syndrome. Since it is autosomal dominant, individuals with the disorder will have at least one dominant allele (e.g., 'N'). Those without the disorder will have two recessive alleles (e.g., 'nn'). Assign genotypes based on the presence or absence of the syndrome.

Step 4: Consider the ABO blood type information. ABO blood type is inherited independently of nail–patella syndrome, but it can provide additional clues about the genotypes of III-6 and III-8. Use the blood type information to refine the genetic analysis if necessary.

Step 5: Combine the information. Based on the pedigree and the inheritance patterns, explain why III-6 has nail–patella syndrome (likely inherited the dominant allele 'N') and III-8 does not (likely inherited two recessive alleles 'nn'). Provide the genotypes for both individuals, including their nail–patella syndrome alleles and ABO blood type alleles.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Autosomal Dominant Inheritance

Nail-patella syndrome is inherited in an autosomal dominant manner, meaning that only one copy of the mutated gene from an affected parent can cause the disorder. This type of inheritance typically results in the condition appearing in every generation, as affected individuals have a 50% chance of passing the trait to their offspring.

Genotype and Phenotype

The genotype refers to the genetic makeup of an individual, while the phenotype is the observable expression of that genotype. In the case of nail-patella syndrome, an individual with the genotype 'Nn' (where 'N' is the normal allele and 'n' is the mutated allele) will express the syndrome, whereas an individual with the genotype 'NN' will not.

Pedigree Analysis

Pedigree analysis is a diagrammatic method used to trace the inheritance of traits through generations in a family. By examining the pedigree provided, one can determine the genotypes of individuals based on their phenotypes and the patterns of inheritance, helping to explain why certain family members exhibit or do not exhibit the syndrome.

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Related Practice

Textbook Question

Nail–patella syndrome is an autosomal disorder affecting the shape of nails on fingers and toes as well as the structure of kneecaps. The pedigree below shows the transmission of nail–patella syndrome in a family along with ABO blood type.

Explain why III-11 has nail–patella syndrome and III-12 does not. Give genotypes for these two individuals.

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Textbook Question

Does this family give evidence of genetic linkage between nail–patella syndrome and ABO blood group? Why or why not?

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Textbook Question

Is nail–patella syndrome a dominant or a recessive condition? Explain your reasoning.

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Textbook Question

Mendel crossed peas having green seeds with peas having yellow seeds. The F₁ generation produced only yellow seeds. In the F₂, the progeny consisted of 6022 plants with yellow seeds and 2001 plants with green seeds. Of the F₂ yellow-seeded plants, 519 were self-fertilized with the following results: 166 bred true for yellow and 353 produced an F₃ ratio of 3/4 yellow: 1/4 green. Explain these results by diagramming the crosses.

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Textbook Question

Using N and n to represent alleles at the nail–patella locus and Iᴬ, Iᴮ and i to represent ABO alleles, write the genotypes of I-1 and I-2 as well as their five children in generation II.

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Textbook Question

Consider this human pedigree for a vision defect.

What is the most probable mode of inheritance of the disease? Identify any discrepancies between the pedigree and your proposed mode of transmission, and provide possible explanations for these exceptions.

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Textbook Question

The accompanying pedigree shows the transmission of albinism (absence of skin pigment) in a human family.

One child of female I-3 has albinism. What is the probability that any of the other four children are carriers of the allele for albinism?

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Textbook Question

The accompanying pedigree shows the transmission of albinism (absence of skin pigment) in a human family.

What is the probability that female I-3 is a heterozygous carrier of the allele for albinism?

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