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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1:41 minutes

Problem 14e

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.

Verified step by step guidance

Step 1: Understand the inheritance pattern of nail–patella syndrome. It is described as an autosomal dominant disorder, meaning that only one copy of the dominant allele is required for an individual to express the trait. If an individual inherits the dominant allele from either parent, they will have the syndrome.

Step 2: Analyze the pedigree provided. Look for the transmission of the nail–patella syndrome trait across generations. Identify whether III-11 and III-12 inherited the dominant allele associated with the syndrome from their parents.

Step 3: Determine the genotype for nail–patella syndrome. Since it is autosomal dominant, individuals with the syndrome will have at least one dominant allele (e.g., Nn or NN), while individuals without the syndrome will have two recessive alleles (nn). Assign the appropriate genotype to III-11 and III-12 based on their phenotype (presence or absence of the syndrome).

Step 4: Consider the ABO blood type information provided in the pedigree. ABO blood type is inherited independently of nail–patella syndrome, but it can help confirm parental inheritance patterns. Use the blood type information to verify the genetic relationship between III-11, III-12, and their parents.

Step 5: Combine the information about nail–patella syndrome and ABO blood type to explain why III-11 has the syndrome (likely inherited the dominant allele) and III-12 does not (likely inherited two recessive alleles). Ensure the genotypes for both individuals are consistent with the inheritance patterns observed in the pedigree.

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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 being expressed in every generation, and both males and females are equally likely to be affected. Understanding this pattern is crucial for determining the genotypes of individuals in the pedigree.

Genotype and Phenotype

The genotype refers to the genetic constitution of an individual, while the phenotype is the observable physical or biochemical characteristics. In the case of nail-patella syndrome, an individual with at least one dominant allele (N) will exhibit the syndrome, while those with two recessive alleles (nn) will not. Identifying the genotypes of III-11 and III-12 helps clarify why one has the syndrome and the other does 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 relationships between individuals and infer their genotypes based on the presence or absence of the syndrome. This analysis is essential for understanding how the trait is passed down and for predicting the likelihood of occurrence in future generations.

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Textbook Question

In mice, black coat color is dominant to white coat color. In the pedigree shown here, mice with a black coat are represented by darkened symbols, and those with white coats are shown as open symbols. Using allele symbols B and b, determine the genotypes for each mouse.

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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.

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

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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

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

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