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Ch. 2 - Transmission Genetics
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 2 - Transmission GeneticsProblem 12b
Chapter 2, Problem 12b

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.
Choose symbols for each allele, and identify the genotypes of the brown male and the two black females.

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1
Step 1: Define the symbols for the alleles. Let 'B' represent the dominant allele for black fur and 'b' represent the recessive allele for brown fur. Black fur is dominant over brown fur.
Step 2: Analyze the offspring from Black Female 1. The litter consists of 9 black and 7 brown pups. This indicates that Black Female 1 must be heterozygous (Bb), as she produces both black and brown offspring when mated with the brown male.
Step 3: Determine the genotype of the brown male. Since the male mouse has brown fur, he must be homozygous recessive (bb), as brown fur is recessive and requires two copies of the 'b' allele.
Step 4: Analyze the offspring from Black Female 2. The litter consists of 14 black pups and no brown pups. This suggests that Black Female 2 is homozygous dominant (BB), as she only produces black offspring regardless of the male's genotype.
Step 5: Summarize the genotypes: The brown male is bb, Black Female 1 is Bb, and Black Female 2 is BB. These genotypes explain the observed offspring ratios in the litters.

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Key Concepts

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

Mendelian Genetics

Mendelian genetics is the study of how traits are inherited through generations based on the principles established by Gregor Mendel. It involves understanding dominant and recessive alleles, where dominant alleles mask the expression of recessive ones. This framework helps predict offspring traits based on parental genotypes.
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Descriptive Genetics

Alleles and Genotypes

Alleles are different forms of a gene that determine specific traits, such as fur color in mice. Each individual has two alleles for each gene, one inherited from each parent, which together form the genotype. The genotype influences the phenotype, or observable traits, of the organism.
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New Alleles and Migration

Punnett Squares

Punnett squares are a tool used in genetics to predict the probability of offspring genotypes from parental genotypes. By organizing the possible allele combinations from each parent, Punnett squares help visualize the inheritance patterns and determine the expected ratios of different phenotypes in the offspring.
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Chi Square Analysis
Related Practice
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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Textbook Question

Black skin color is dominant to pink skin color in pigs. Two heterozygous black pigs are crossed.

If these pigs produce a total of three piglets, what is the probability that two will be pink and one will be black?

595
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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?

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Textbook Question

The following figure shows the results of Mendel's test-cross analysis of independent assortment. In this experiment, he first crossed pure-breeding round, yellow plants to pure-breeding wrinkled, green plants. The round yellow are crossed to pure-breeding wrinkled, green plants. Use chi-square analysis to show that Mendel's results do not differ significantly from those expected.

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Textbook Question

An experienced goldfish breeder receives two unusual male goldfish. One is black rather than gold, and the other has a single tail fin rather than a split tail fin. The breeder crosses the black male with a female that is gold. All the F₁ are gold. She also crosses the single-finned male to a female with a split tail fin. All the F₁ have a split tail fin. She then crosses the black male to F₁ gold females and, separately, crosses the single-finned male to F₁ split-finned females. The results of the crosses are shown below.


  Black male x F₁ gold female:

    Gold        32

    Black       34

  Single-finned male x F₁ split-finned female:

    Split fin       41

    Single fin    39

What do the results of these crosses suggest about the inheritance of color and tail fin shape in goldfish?

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Textbook Question

An experienced goldfish breeder receives two unusual male goldfish. One is black rather than gold, and the other has a single tail fin rather than a split tail fin. The breeder crosses the black male to a female that is gold. All the F₁ are gold. She also crosses the single-finned male to a female with a split tail fin. All the F₁ have a split tail fin. She then crosses the black male to F₁ gold females and, separately, crosses the single-finned male to F₁ split-finned females. The results of the crosses are shown below.

Is black color dominant or recessive? Explain. Is single tail dominant or recessive? Explain.

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