Textbook Question
Black skin color is dominant to pink skin color in pigs. Two heterozygous black pigs are crossed.
What is the probability that their offspring will have pink skin?
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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 10c
The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.
Cross 1: P₁: Male leopard x male mottled
F₁: All mottled
F₂: 70 mottled, 22 leopard
Cross 2: P₁: Male mottled x female leopard
F₁: All mottled
F₂: 50 mottled, 18 leopard
In the F₂ progeny from both crosses, what proportion is expected to be homozygous? What proportion is expected to be heterozygous?
Verified step by step guidance1
Step 1: Identify the inheritance pattern of the trait. Since the trait is autosomal and the F₁ generation in both crosses is uniformly mottled, this suggests that the mottled phenotype is dominant over the leopard phenotype.
Step 2: Assign genotypes to the parental (P₁) generation. Pure-breeding populations indicate homozygosity. Therefore, the male leopard is homozygous recessive (aa), and the male mottled is homozygous dominant (AA). Similarly, the female leopard is homozygous recessive (aa), and the female mottled is homozygous dominant (AA).
Step 3: Determine the genotypes of the F₁ generation. In both crosses, the F₁ offspring are all mottled, which means they are heterozygous (Aa), inheriting one dominant allele (A) from the mottled parent and one recessive allele (a) from the leopard parent.
Step 4: Predict the genotypes of the F₂ generation using a Punnett square. Cross two heterozygous individuals (Aa x Aa) to determine the expected genotypic ratios: 1 homozygous dominant (AA), 2 heterozygous (Aa), and 1 homozygous recessive (aa).
Step 5: Calculate the proportions of homozygous and heterozygous individuals in the F₂ generation. Based on the Punnett square, 1/4 of the progeny are homozygous dominant (AA), 1/4 are homozygous recessive (aa), and 2/4 (or 1/2) are heterozygous (Aa).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Autosomal Inheritance
Autosomal inheritance refers to the transmission of genes located on the autosomes, which are the non-sex chromosomes. Traits controlled by autosomal genes can be dominant or recessive. In this case, the dorsal pigment pattern in frogs is determined by an autosomal gene, influencing the phenotypic expression of either leopard or mottled patterns based on the alleles inherited from the parents.
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Autosomal Pedigrees
Genotypic Ratios in Mendelian Genetics
Mendelian genetics describes how traits are inherited through specific ratios based on parental genotypes. In a typical monohybrid cross, the expected genotypic ratio for a trait controlled by a single gene is 1 homozygous dominant: 2 heterozygous: 1 homozygous recessive. Understanding these ratios is crucial for predicting the proportions of homozygous and heterozygous individuals in the F₂ generation from the given crosses.
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Reciprocal Crosses
Reciprocal crosses involve switching the sexes of the parents in a genetic cross to determine if the inheritance pattern is influenced by sex. In this scenario, both crosses yield the same F₁ generation (all mottled), indicating that the mottled trait is likely dominant. Analyzing the F₂ progeny from both crosses helps confirm the inheritance pattern and calculate the expected proportions of homozygous and heterozygous individuals.
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Related Practice
Textbook Question
In the datura plant, purple flower color is controlled by a dominant allele, P. White flowers are found in plants homozygous for the recessive allele p. Suppose that a purple-flowered datura plant with an unknown genotype is self-fertilized and that its progeny are 28 purple-flowered plants and 10 white-flowered plants.
If one of the purple-flowered progeny plants is selected at random and self-fertilized, what is the probability it will breed true?
Textbook Question
The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.
Cross 1: P₁: Male leopard x male mottled
F₁: All mottled
F₂: 70 mottled, 22 leopard
Cross 2: P₁: Male mottled x female leopard
F₁: All mottled
F₂: 50 mottled, 18 leopard
Which of the phenotypes is dominant? Explain your answer.
Textbook Question
The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.
Cross 1: P₁: Male leopard x male mottled
F₁: All mottled
F₂: 70 mottled, 22 leopard
Cross 2: P₁: Male mottled x female leopard
F₁: All mottled
F₂: 50 mottled, 18 leopard
Compare and contrast the results of the reciprocal crosses in the context of autosomal gene inheritance.
Textbook Question
The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.
Cross 1: P₁: Male leopard x male mottled
F₁: All mottled
F₂: 70 mottled, 22 leopard
Cross 2: P₁: Male mottled x female leopard
F₁: All mottled
F₂: 50 mottled, 18 leopard
Propose two different genetic crosses that would allow you to determine the genotype of one mottled frog from the F₂ generation.
Textbook Question
Black skin color is dominant to pink skin color in pigs. Two heterozygous black pigs are crossed.
What is the probability that the first and second offspring will have black skin?
5
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