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?
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2. Mendel's Laws of Inheritance
Monohybrid Cross
2:17 minutesProblem 12a
Textbook Question
A male mouse with brown fur color is mated to two different female mice with black fur. Black female 1 produces a litter of 9 black and 7 brown pups. Black female 2 produces 14 black pups.
What is the mode of inheritance of black and brown fur color in mice?
Verified step by step guidance1
Step 1: Begin by analyzing the phenotypes of the offspring produced by each mating. Black female 1 produces both black and brown pups, while Black female 2 produces only black pups. This suggests that the inheritance pattern may involve dominance and recessiveness.
Step 2: Hypothesize the genetic basis of fur color. Assume that black fur (B) is dominant and brown fur (b) is recessive. This means that a mouse with the genotype BB or Bb will have black fur, while a mouse with the genotype bb will have brown fur.
Step 3: Analyze the mating between the male mouse (brown fur, likely bb) and Black female 1. The presence of both black and brown pups suggests that Black female 1 is heterozygous (Bb). When crossed with the bb male, the offspring would have a 1:1 ratio of Bb (black) and bb (brown).
Step 4: Analyze the mating between the male mouse (bb) and Black female 2. The fact that all offspring are black suggests that Black female 2 is homozygous dominant (BB). When crossed with the bb male, all offspring would inherit one B allele and one b allele, resulting in the Bb genotype (black fur).
Step 5: Conclude that the mode of inheritance for black and brown fur color in mice is autosomal dominance, where black fur is dominant (B) and brown fur is recessive (b). The observed offspring ratios support this inheritance pattern.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mendelian Inheritance
Mendelian inheritance refers to the principles of heredity established by Gregor Mendel, which include concepts such as dominant and recessive traits. In this case, the fur color in mice is likely governed by these principles, where one color (black) is dominant over the other (brown). Understanding these basic inheritance patterns is crucial for analyzing the offspring's phenotypes.
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Genotype and Phenotype
The genotype is the genetic makeup of an organism, while the phenotype is the observable physical characteristics resulting from the genotype. In this scenario, the black fur color is the phenotype that can arise from different genotypes, including homozygous dominant or heterozygous combinations. Analyzing the offspring's phenotypes helps infer the parental genotypes.
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Punnett Square
A Punnett square is a diagram used to predict the genetic outcomes of a cross between two organisms. It helps visualize the possible combinations of alleles from the parents and their resulting phenotypes in the offspring. By applying a Punnett square to the mating of the brown male and black females, one can deduce the inheritance pattern of fur color in the pups.
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