Textbook Question
For the cross Aabb × aaBb, what is the expected genotype ratio? What is the expected phenotype ratio?
Ch. 2 - Transmission Genetics
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 2, Problem 4
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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Identify the dominant and recessive alleles: Black coat color is dominant (B) and white coat color is recessive (b). Therefore, mice with black coats can have genotypes BB or Bb, while white-coated mice must be bb.
Examine the pedigree symbols: Darkened symbols represent black-coated mice, and open symbols represent white-coated mice. Assign the genotype bb to all white-coated (open) mice since they must be homozygous recessive.
Analyze the parents and offspring relationships: For each mating pair, use the phenotypes of their offspring to infer the parents' genotypes. For example, if two black-coated mice have a white-coated offspring, both parents must be heterozygous (Bb) to pass on the recessive allele b.
Use Mendelian inheritance rules: Recall that offspring receive one allele from each parent. Use Punnett squares or probability to determine possible genotypes of each mouse based on their phenotype and the genotypes of their relatives.
Assign genotypes to all mice in the pedigree: Starting from known genotypes (white mice as bb), work through the pedigree step-by-step, deducing the genotype of each black-coated mouse as either BB or Bb based on the presence or absence of white offspring and the genotypes of their mates.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Dominant and Recessive Alleles
Dominant alleles express their trait even if only one copy is present, while recessive alleles require two copies to show their trait. In this case, black coat color (B) is dominant over white coat color (b), meaning mice with BB or Bb genotypes have black coats, and only bb mice have white coats.
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Variations on Dominance
Genotype vs. Phenotype
Phenotype refers to the observable traits, such as coat color, while genotype is the genetic makeup that determines these traits. Understanding the difference helps in deducing the genotype of each mouse based on their phenotype and inheritance patterns.
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Pedigree Analysis
A pedigree chart tracks the inheritance of traits across generations. By analyzing the pattern of black and white coat colors in the pedigree, one can infer the possible genotypes of each mouse using principles of Mendelian inheritance.
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Related Practice
Textbook Question
Compare and contrast the following terms:
Dihybrid cross and Trihybrid cross
Textbook Question
A man, J.B., has a sister with autosomal recessive galactosemia (OMIM 230400), and his partner, S.B., has a brother with galactosemia. Galactosemia is a serious condition caused by an enzyme deficiency that prevents the metabolism of the sugar galactose. Neither J.B. nor S.B. has galactosemia, but they are concerned about the risk that a future child of theirs will have the condition. What is the probability their first child will have galactosemia?
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Textbook Question
For the cross BB×Bb, what is the expected genotype ratio? What is the expected phenotype ratio?
Textbook Question
A woman, S.R., had a maternal grandfather with hemophilia A (OMIM 306700), an X-linked recessive condition that reduces blood clotting. S.R.'s maternal grandmother and paternal grandparents are free of the condition, as are her partner, his parents, and his grandparents. S.R. has no siblings. She wants to know the chance that a son of hers will have the condition. What is that probability?
Textbook Question
Two parents plan to have three children. What is the probability that the children will be two girls and one boy?
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